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AUTHOR Kleger, Nicole and Cihova, Martina and Masania, Kunal and Studart, André R. and Löffler, Jörg F.
Title 3d printing of salt as a template for magnesium with structured porosity [Abstract]
Year 2019
Journal/Proceedings advanced materials
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Abstract Porosity is an essential feature in a wide range of applications that combine light weight with high surface area and tunable density. Porous materials can be easily prepared with a vast variety of chemistries using the salt-leaching technique. However, this templating approach has so far been limited to the fabrication of structures with random porosity and relatively simple macroscopic shapes. Here, a technique is reported that combines the ease of salt leaching with the complex shaping possibilities given by additive manufacturing (AM). By tuning the composition of surfactant and solvent, the salt-based paste is rheologically engineered and printed via direct ink writing into grid-like structures displaying structured pores that span from the sub-millimeter to the macroscopic scale. As a proof of concept, dried and sintered NaCl templates are infiltrated with magnesium (Mg), which is typically highly challenging to process by conventional AM techniques due to its highly oxidative nature and high vapor pressure. Mg scaffolds with well-controlled, ordered porosity are obtained after salt removal. The tunable mechanical properties and the potential to be predictably bioresorbed by the human body make these Mg scaffolds attractive for biomedical implants and demonstrate the great potential of this additive technique.
AUTHOR Zhang, Danwei and Jonhson, Win and Herng, Tun Seng and Ang, Yong Quan and Yang, Lin and Tan, Swee Ching and Peng, Erwin and He, Hui and Ding, Jun
Title A 3D-printing method of fabrication for metals{,} ceramics{,} and multi-materials using a universal self-curable technique for robocasting [Abstract]
Year 2019
Journal/Proceedings Materials Horizons
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Ceramics and metals are important materials that modern technologies are constructed from. The capability to produce such materials in a complex geometry with good mechanical properties can revolutionize the way we engineer our devices. Current curing techniques pose challenges such as high energy requirements{,} limitations of materials with high refractive index{,} tedious post-processing heat treatment processes{,} uneven drying shrinkages{,} and brittleness of green bodies. In this paper{,} a novel modified self-curable epoxide–amine 3D printing system is proposed to print a wide range of ceramics (metal oxides{,} nitrides{,} and carbides) and metals without the need for an external curing source. Through this technique{,} complex multi-material structures (with metal–ceramic and ceramic–ceramic combinations) can also be realized. Tailoring and matching the sintering temperatures of different materials through sintering additives and dopants{,} combined with a structural design providing maximum adhesion between interfaces{,} allow us to successfully obtain superior quality sintered multi-material structures. High-quality ceramic and metallic materials have been achieved (e.g.{,} zirconia with >98% theoretical density). Also{,} highly conductive metals and magnetic ceramics were printed and shaped uniquely without the need for a sacrificial support. With the addition of low molecular weight plasticizers and a multi-stage heat treatment process{,} crack-free and dense high-quality integrated multi-material structures fabricated by 3D printing can thus be a reality in the near future.
AUTHOR Kajtez, Janko and Wesseler, Milan Finn and Birtele, Marcella and Khorasgani, Farinaz Riyahi and Rylander Ottosson, Daniella and Heiskanen, Arto and Kamperman, Tom and Leijten, Jeroen and Martínez-Serrano, Alberto and Larsen, Niels B. and Angelini, Thomas E. and Parmar, Malin and Lind, Johan U. and Emnéus, Jenny
Title Embedded 3D Printing in Self-Healing Annealable Composites for Precise Patterning of Functionally Mature Human Neural Constructs [Abstract]
Year 2022
Journal/Proceedings Advanced Science
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Abstract Human in vitro models of neural tissue with tunable microenvironment and defined spatial arrangement are needed to facilitate studies of brain development and disease. Towards this end, embedded printing inside granular gels holds great promise as it allows precise patterning of extremely soft tissue constructs. However, granular printing support formulations are restricted to only a handful of materials. Therefore, there has been a need for novel materials that take advantage of versatile biomimicry of bulk hydrogels while providing high-fidelity support for embedded printing akin to granular gels. To address this need, Authors present a modular platform for bioengineering of neuronal networks via direct embedded 3D printing of human stem cells inside Self-Healing Annealable Particle-Extracellular matrix (SHAPE) composites. SHAPE composites consist of soft microgels immersed in viscous extracellular-matrix solution to enable precise and programmable patterning of human stem cells and consequent generation mature subtype-specific neurons that extend projections into the volume of the annealed support. The developed approach further allows multi-ink deposition, live spatial and temporal monitoring of oxygen levels, as well as creation of vascular-like channels. Due to its modularity and versatility, SHAPE biomanufacturing toolbox has potential to be used in applications beyond functional modeling of mechanically sensitive neural constructs.
AUTHOR Kessel, Benjamin and Lee, Mihyun and Bonato, Angela and Tinguely, Yann and Tosoratti, Enrico and Zenobi-Wong, Marcy
Title 3D Bioprinting of Macroporous Materials Based on Entangled Hydrogel Microstrands [Abstract]
Year 2020
Journal/Proceedings Advanced Science
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Abstract Hydrogels are excellent mimetics of mammalian extracellular matrices and have found widespread use in tissue engineering. Nanoporosity of monolithic bulk hydrogels, however, limits mass transport of key biomolecules. Microgels used in 3D bioprinting achieve both custom shape and vastly improved permissivity to an array of cell functions, however spherical-microbead-based bioinks are challenging to upscale, are inherently isotropic, and require secondary crosslinking. Here, bioinks based on high-aspect-ratio hydrogel microstrands are introduced to overcome these limitations. Pre-crosslinked, bulk hydrogels are deconstructed into microstrands by sizing through a grid with apertures of 40–100 µm. The microstrands are moldable and form a porous, entangled structure, stable in aqueous medium without further crosslinking. Entangled microstrands have rheological properties characteristic of excellent bioinks for extrusion bioprinting. Furthermore, individual microstrands align during extrusion and facilitate the alignment of myotubes. Cells can be placed either inside or outside the hydrogel phase with >90% viability. Chondrocytes co-printed with the microstrands deposit abundant extracellular matrix, resulting in a modulus increase from 2.7 to 780.2 kPa after 6 weeks of culture. This powerful approach to deconstruct bulk hydrogels into advanced bioinks is both scalable and versatile, representing an important toolbox for 3D bioprinting of architected hydrogels.
AUTHOR Zhang, Danwei and Peng, Erwin and Borayek, Ramadan and Ding, Jun
Title Controllable Ceramic Green-Body Configuration for Complex Ceramic Architectures with Fine Features [Abstract]
Year 2019
Journal/Proceedings Advanced Functional Materials
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Abstract Fabrication of dense ceramic articles with intricate fine features and geometrically complex morphology by using a relatively simple and the cost-effective process still remains a challenge. Ceramics, either in its green- or sintered-form, are known for being hard yet brittle which limits further shape reconfiguration. In this work, a combinatorial process of ceramic robocasting and photopolymerization is demonstrated to produce either flexible and/or stretchable ceramic green-body (Flex-Body or Stretch-Body) that can undergo a postprinting reconfiguration process. Secondary shaping may proceed through: i) self-assembly-assisted shaping and ii) mold-assisted shaping process, which allows a well-controlled ceramic structure morphology. With a proposed well-controlled thermal heating process, the ceramic Sintered-Body can achieve >99.0% theoretical density with good mechanical rigidity. Complex and dense ceramic articles with fine features down to 65 μm can be fabricated. When combined with a multi-nozzle deposition process, i) self-shaping ceramic structures can be realized through anisotropic shrinkage induced by suspensions' composition variation and ii) technical and functional multiceramic structures can be fabricated. The simplicity of the proposed technique and its inexpensive processing cost make it an attractive approach for fabricating geometrically complex ceramic articles with unique macrostructures, which complements the existing state of-the-art ceramic additive manufacturing techniques.
AUTHOR Kokkinis, Dimitri and Bouville, Florian and Studart, André R.
Title 3D Printing of Materials with Tunable Failure via Bioinspired Mechanical Gradients [Abstract]
Year 2018
Journal/Proceedings Advanced Materials
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Abstract Mechanical gradients are useful to reduce strain mismatches in heterogeneous materials and thus prevent premature failure of devices in a wide range of applications. While complex graded designs are a hallmark of biological materials, gradients in manmade materials are often limited to 1D profiles due to the lack of adequate fabrication tools. Here, a multimaterial 3D‐printing platform is developed to fabricate elastomer gradients spanning three orders of magnitude in elastic modulus and used to investigate the role of various bioinspired gradient designs on the local and global mechanical behavior of synthetic materials. The digital image correlation data and finite element modeling indicate that gradients can be effectively used to manipulate the stress state and thus circumvent the weakening effect of defect‐rich interfaces or program the failure behavior of heterogeneous materials. Implementing this concept in materials with bioinspired designs can potentially lead to defect‐tolerant structures and to materials whose tunable failure facilitates repair of biomedical implants, stretchable electronics, or soft robotics.
AUTHOR Schaffner, Manuel and R{"u}hs, Patrick A. and Coulter, Fergal and Kilcher, Samuel and Studart, Andr{'e} R.
Title 3D printing of bacteria into functional complex materials [Abstract]
Year 2017
Journal/Proceedings Science Advances
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Despite recent advances to control the spatial composition and dynamic functionalities of bacteria embedded in materials, bacterial localization into complex three-dimensional (3D) geometries remains a major challenge. We demonstrate a 3D printing approach to create bacteria-derived functional materials by combining the natural diverse metabolism of bacteria with the shape design freedom of additive manufacturing. To achieve this, we embedded bacteria in a biocompatible and functionalized 3D printing ink and printed two types of {textquotedblleft}living materials{textquotedblright} capable of degrading pollutants and of producing medically relevant bacterial cellulose. With this versatile bacteria-printing platform, complex materials displaying spatially specific compositions, geometry, and properties not accessed by standard technologies can be assembled from bottom up for new biotechnological and biomedical applications.
AUTHOR Kuthe, Sudhanshu and Schlothauer, Arthur and Bodkhe, Sampada and Hulme, Christopher and Ermanni, Paolo
Title 3D printed mechanically representative aortic model made of gelatin fiber reinforced silicone composite [Abstract]
Year 2022
Journal/Proceedings Materials Letters
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Additive manufacturing (AM) is a useful technology to produce artificial aortic models for the training of transcatheter aortic valve replacement (TAVR) surgery. With AM, the models can be tailored towards the individualized aortic anatomy of patients. Most of these reported models so far are manufactured using single rubber-like materials. However, such materials do not replicate the mechanical properties of natural aortic tissue, especially the stress–strain response in higher strain (>0.1) regions. This could be problematic for surgeons training for surgeries using a model which does not exhibit properties of the real aorta. To overcome this limitation, we developed a 3D-printed, mechanically representative aortic model comprising gelatin fibers and silicone. The model is promising as a realistic analog of aortic sinus for mock TAVR surgery. Computerized tomography data was analyzed beforehand using medical imaging to identify the anatomy of a specific patient’s aortic sinus and the surrounding blood vessels. A novel silicone matrix composite reinforced with gelatin fibers designed in this work was tested and compared with the stress–strain response of aortic tissue. Such a model comprising both patient-specific geometries as well as realistic material properties of aortic tissue can be helpful for the development of next-generation medical phantoms.
AUTHOR Kamdem Tamo, Arnaud and Tran, Tuan Anh and Doench, Ingo and Jahangir, Shaghayegh and Lall, Aastha and David, Laurent and Peniche-Covas, Carlos and Walther, Andreas and Osorio-Madrazo, Anayancy
Title 3D Printing of Cellulase-Laden Cellulose Nanofiber/Chitosan Hydrogel Composites: Towards Tissue Engineering Functional Biomaterials with Enzyme-Mediated Biodegradation [Abstract]
Year 2022
Journal/Proceedings Materials
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The 3D printing of a multifunctional hydrogel biomaterial with bioactivity for tissue engineering, good mechanical properties and a biodegradability mediated by free and encapsulated cellulase was proposed. Bioinks of cellulase-laden and cellulose nanofiber filled chitosan viscous suspensions were used to 3D print enzymatic biodegradable and biocompatible cellulose nanofiber (CNF) reinforced chitosan (CHI) hydrogels. The study of the kinetics of CNF enzymatic degradation was studied in situ in fibroblast cell culture. To preserve enzyme stability as well as to guarantee its sustained release, the cellulase was preliminarily encapsulated in chitosan–caseinate nanoparticles, which were further incorporated in the CNF/CHI viscous suspension before the 3D printing of the ink. The incorporation of the enzyme within the CHI/CNF hydrogel contributed to control the decrease of the CNF mechanical reinforcement in the long term while keeping the cell growth-promoting property of chitosan. The hydrolysis kinetics of cellulose in the 3D printed scaffolds showed a slow but sustained degradation of the CNFs with enzyme, with approximately 65% and 55% relative activities still obtained after 14 days of incubation for the encapsulated and free enzyme, respectively. The 3D printed composite hydrogels showed excellent cytocompatibility supporting fibroblast cell attachment, proliferation and growth. Ultimately, the concomitant cell growth and biodegradation of CNFs within the 3D printed CHI/CNF scaffolds highlights the remarkable potential of CHI/CNF composites in the design of tissue models for the development of 3D constructs with tailored in vitro/in vivo degradability for biomedical applications.
AUTHOR Kitana, Waseem and Apsite, Indra and Hazur, Jonas and Boccaccini, Aldo R. and Ionov, Leonid
Title 4D Biofabrication of T-Shaped Vascular Bifurcation [Abstract]
Year 2022
Journal/Proceedings Advanced Materials Technologies
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Abstract 4D Biofabrication – a pioneering biofabrication technique – involves the automated fabrication of 3D constructs that are dynamic and show shape-transformation capability. Although current 4D biofabrication methods are highly promising for the fabrication of vascular elements such as tubes, the fabrication of tubular junctions is still highly challenging. Here, for the first time, a 4D biofabrication-based concept for the fabrication of a T-shaped vascular bifurcation using 3D printed shape-changing layers based on a mathematical model is reported. The formation of tubular structures with various diameters is achieved by precisely controlling the parameters (e.g. crosslinking time). Consequently, the 3D printed films show self-transformation into a T-junction upon immersion in water with a diameter of a few millimeters. Perfusion of the tubular T-junction with an aqueous medium simulating blood flow through vessels shows minimal leakages with a maximum flow velocity of 0.11 m s–1. Furthermore, human umbilical vein endothelial cells seeded on the inner surface of the plain T-junction show outstanding growth properties and excellent cell viability. The achieved diameters are comparable to the native blood vessels, which is still a challenge in 3D biofabrication. This approach paves the way for the fabrication of fully automatic self-actuated vascular bifurcations as vascular grafts.
AUTHOR Govindharaj, Mano and Al Hashemi, Noura Sayed and Soman, Soja Saghar and Vijayavenkataraman, Sanjairaj
Title Bioprinting of bioactive tissue scaffolds from ecologically-destructive fouling tunicates [Abstract]
Year 2022
Journal/Proceedings Journal of Cleaner Production
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Urochordates are the closest invertebrate relative to humans and commonly referred to as tunicates, a name ascribed to their leathery outer “tunic”. The tunic is the outer covering of the organism which functions as the exoskeleton and is rich in carbohydrates and proteins. Invasive or fouling tunicates pose a great threat to the indigenous marine ecosystem and governments spend several hundred thousand dollars for tunicate management, considering the huge adverse economic impact it has on the shipping and fishing industries. In this work, the environmentally destructive colonizing tunicate species of Polyclinum constellatum was successfully identified in the coast of Abu Dhabi and methods of sustainably using it as wound-dressing materials, decellularized extra-cellular matrix (dECM) scaffolds for tissue engineering applications and bioinks for bioprinting of tissue constructs for regenerative medicine are proposed. The intricate three-dimensional nanofibrous cellulosic networks in the tunic remain intact even after the multi-step process of decellularization and lyophilization. The lyophilized dECM tunics possess excellent biocompatibility and remarkable tensile modulus of 3.85 ± 0.93 MPa compared to ∼0.1–1 MPa of other hydrogel systems. This work demonstrates the use of lyophilized tunics as wound-dressing materials, having outperformed the commercial dressing materials with a capacity of absorbing 20 times its weight in the dry state. This work also demonstrates the biocompatibility of dECM scaffold and dECM-derived bioink (3D bioprinting with Mouse Embryonic Fibroblasts (MEFs)). Both dECM scaffolds and bioprinted dECM-based tissue constructs show enhanced metabolic activity and cell proliferation over time. Sustainable utilization of dECM-based biomaterials from ecologically-destructive fouling tunicates proposed in this work helps preserve the marine ecosystem, shipping and fishing industries worldwide, and mitigate the huge cost spent for tunicate management.
AUTHOR Strauß, Svenja and Schroth, Bianca and Hubbuch, Jürgen
Title Evaluation of the Reproducibility and Robustness of Extrusion-Based Bioprinting Processes Applying a Flow Sensor [Abstract]
Year 2022
Journal/Proceedings Frontiers in bioengineering and biotechnology
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Bioprinting is increasingly regarded as a suitable additive manufacturing method in biopharmaceutical process development and formulation. In order to manage the leap from research to industrial application, higher levels of reproducibility and a standardized bioprinting process are prerequisites. This said, the concept of process analytical technologies, standard in the biopharmaceutical industry, is still at its very early steps. To date most extrusion-based printing processes are controlled over penumatic pressure and thus not adaptive to environmental or system related changes over several experimental runs. A constant set pressure applied over a number of runs, might lead to variations in flow rate and thus to unreliable printed constructs. With this in mind, the simple question arises whether a printing process based on a set flow rate could improve reproduciblity and transfer to different printing systems. The control and monitoring of flow rate aim to introduce the concept of PAT in the field of bioprinting. This study investigates the effect of different processing modes (set pressure vs. set flow rate) on printing reproducibility occurring during an extrusion-based printing process consisting of 6 experimental runs consisting of 3 printed samples each. Additionally, the influence of different filling levels of the ink containing cartridge during a printing process was determined. Different solutions based on a varying amount of alginate polymer and Kolliphor hydrogels in varying concentrations showed the need for individual setting of printing parameter. To investigate parameter transferability among different devices two different printers were used and the flow was monitored using a flow sensor attached to the printing unit. It could be demonstrated that a set flow rate controlled printing process improved accuracy and the filling level also affects the accuracy of printing, the magnitude of this effects varies as the cartridge level declined. The transferability between printed devices was eased by setting the printing parameters according to a set flow rate of each bioink disregarding the value of the set pressure. Finally, by a bioprinting porcess control based on a set flow rate, the coefficient of variance for printed objects could be reduced from 0.2 to 0.02 for 10% (w/v) alginate polymer solutions.
AUTHOR Neubauer, Vanessa J. and Hüter, Florian and Wittmann, Johannes and Trossmann, Vanessa T. and Kleinschrodt, Claudia and Alber-Laukant, Bettina and Rieg, Frank and Scheibel, Thomas
Title Flow Simulation and Gradient Printing of Fluorapatite- and Cell-Loaded Recombinant Spider Silk Hydrogels [Abstract]
Year 2022
Journal/Proceedings Biomolecules
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Hierarchical structures are abundant in almost all tissues of the human body. Therefore, it is highly important for tissue engineering approaches to mimic such structures if a gain of function of the new tissue is intended. Here, the hierarchical structures of the so-called enthesis, a gradient tissue located between tendon and bone, were in focus. Bridging the mechanical properties from soft to hard secures a perfect force transmission from the muscle to the skeleton upon locomotion. This study aimed at a novel method of bioprinting to generate gradient biomaterial constructs with a focus on the evaluation of the gradient printing process. First, a numerical approach was used to simulate gradient formation by computational flow as a prerequisite for experimental bioprinting of gradients. Then, hydrogels were printed in a single cartridge printing set-up to transfer the findings to biomedically relevant materials. First, composites of recombinant spider silk hydrogels with fluorapatite rods were used to generate mineralized gradients. Then, fibroblasts were encapsulated in the recombinant spider silk-fluorapatite hydrogels and gradually printed using unloaded spider silk hydrogels as the second component. Thereby, adjustable gradient features were achieved, and multimaterial constructs were generated. The process is suitable for the generation of gradient materials, e.g., for tissue engineering applications such as at the tendon/bone interface.
AUTHOR Rahimnejad, Maedeh and Adoungotchodo, Atma and Demarquette, Nicole R. and Lerouge, Sophie
Title FRESH bioprinting of biodegradable chitosan thermosensitive hydrogels [Abstract]
Year 2022
Journal/Proceedings Bioprinting
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Thermosensitive chitosan (CH)-based hydrogels prepared with a mix of sodium bicarbonate and β-glycerophosphate as gelling agents rapidly pass from a liquid at room temperature to a mechanically strong solid at body temperature without any crosslinker. They show excellent potential for tissue engineering applications and could be interesting candidates for bioprinting. Unfortunately, since gelation is not instantaneous, formulations compatible with cell encapsulation (chitosan concentrations around 2% or lower) lead to very poor resolution and fidelity due to filament spreading. Here, we investigate the FRESH bioprinting approach with a warm sacrificial support bath, to overcome these limitations and enhance their bioprintability. First, a support bath, made of Pluronic including sodium chloride salt as a rheology modifier agent, was designed to meet the specific physical state requirements (solid at 37 °C and liquid at room temperature) and rheological properties appropriate for bioprinting. This support bath presented yield stress of over 100 Pa, a shear thinning behavior, and fast self-healing during cyclic recovery tests. Three different chitosan hydrogels (CH2%w/v, CH3%w/v, and a mixture of CH and gelatin) were tested for their ability to form filament and 3D structures, with and without a support bath. Both the resolution and mechanical properties of the printed structure were drastically enhanced using the FRESH method, with an approximate four fold decrease of the filament diameter which is close to the needle diameter. The printed structures were easily harvested without altering their shape by cooling down the support bath, and do not swell when immersed in PBS. Live/dead assays confirmed that the viability of encapsulated mesenchymal stem cells was highest in CH2% and that the support bath-assisted bioprinting process did not adversely impact cell viability. This study demonstrates that using a warm FRESH-like approach drastically enhances the potential for bioprinting of the thermosensitive biodegradable chitosan hydrogels and opens up a wide range of applications for 3D models and tissue engineering.
AUTHOR Yan Li and Lijing Huang and Guangpin Tai and Feifei Yan and Lin Cai and Chenxing Xin and Shamoon {Al Islam}
Title Graphene Oxide-loaded magnetic nanoparticles within 3D hydrogel form High-performance scaffolds for bone regeneration and tumour treatment [Abstract]
Year 2022
Journal/Proceedings Composites Part A: Applied Science and Manufacturing
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The treatment of tumour-related bone defects should ideally combine bone regeneration with tumour treatment. Additive manufacturing (AM) could feasibly place functional bone-repair materials within composite materials with functional-grade structures, giving them bone repair and anti-tumour effects. Magnetothermal therapy is a promising non-invasive method of tumour treatment that has attracted increasing attention. In this study, we prepared novel hydrogel composite scaffolds of polyvinyl alcohol/sodium alginate/hydroxyapatite (PVA/SA/HA) at low temperature via AM. The scaffolds were loaded with various concentrations of magnetic graphene oxide (MGO) @Fe3O4 nanoparticles. The scaffolds were characterised by fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM) and thermal gravimetric analysis (TGA), which showed that the scaffolds have good moulding qualities and strong hydrogen bonding between the MGO/PVA/SA/HA components. TGA analysis demonstrated the expected thermal stability of the MGO and scaffolds. Thermal effects can be adjusted by varying the contents of MGO and the strength of an external alternating magnetic field. The prepared MGO hydrogel composite scaffolds enhance biological functions and support bone mesenchymal stem cell differentiation in vitro. The scaffolds also show favourable anti-tumour characteristics with effective magnetothermal conversion in vivo.
AUTHOR Liu, Chuan and Campbell, Scott B. and Li, Jianzhao and Bannerman, Dawn and Pascual-Gil, Simon and Kieda, Jennifer and Wu, Qinghua and Herman, Peter R. and Radisic, Milica
Title High Throughput Omnidirectional Printing of Tubular Microstructures from Elastomeric Polymers [Abstract]
Year 2022
Journal/Proceedings Advanced Healthcare Materials
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Abstract Bioelastomers have been extensively used in biomedical applications due to their desirable mechanical strength, tunable properties, and chemical versatility; however, 3D printing bioelastomers into microscale structures has proven elusive. Herein, a high throughput omnidirectional printing approach via coaxial extrusion is described that fabricated perfusable elastomeric microtubes of unprecedently small inner diameter (350-550 μm) and wall thickness (40-60 μm). The versatility of this approach was shown through the printing of two different polymeric elastomers, followed by photocrosslinking and removal of the fugitive inner phase. Designed experiments were used to tune the dimensions and stiffness of the microtubes to match that of native ex vivo rat vasculature. This approach afforded the fabrication of multiple biomimetic shapes resembling cochlea and kidney glomerulus and afforded facile, high-throughput generation of perfusable structures that can be seeded with endothelial cells for biomedical applications. Post-printing laser micromachining was performed to generate numerous micro-sized holes (5-20 μm) in the tube wall to tune microstructure permeability. Importantly, for organ-on-a-chip applications, the described approach took only 3.6 minutes to print microtubes (without microholes) over an entire 96-well plate device, in contrast to comparable hole-free structures that take between 1.5 to 6.5 days to fabricate using a manual 3D stamping approach. This article is protected by copyright. All rights reserved
AUTHOR Hou, Yanhao and Wang, Weiguang and Bartolo, Paulo
Title Investigation of polycaprolactone for bone tissue engineering scaffolds: in vitro degradation and biological studies [Abstract]
Year 2022
Journal/Proceedings Materials & Design
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Polycaprolactone (PCL) is one of the most recognized polymeric materials used for bone tissue engineering scaffold fabrication. This study aims to evaluate the effects of the molecular weight (Mn) of PCL on the degradation kinematics, surface, microstructural, thermal, mechanical, and biological properties of 3D printed bone scaffolds. Surface properties were investigated considering water-in-air contact angle and nanoindentation tests, while morphological characteristics and degradation kinematics (accelerated degradation tests) were examined using scanning electron microscopy (SEM), pairing with thermal and mechanical properties monitored at each considered time point. A set of mathematical equations describing the variation of fiber diameter, porosity, mechanical properties, and weight, as a function of molecular weight and degradation time, were obtained based on the experimental results. Human adipose-derived stem cells (hADSCs) proliferation and differentiation tests were also conducted using in vitro colorimetric assay. All results indicated that molecular weight had impacts on the surface, mechanical and biological properties of PCL scaffolds, while no significant effects were observed on the degradation rate. Scaffolds with lower molecular weight presented better bio-mechanical properties. These findings provide useful information for the design of polymeric bone tissue engineering scaffolds.
AUTHOR Kim, Jieun and Lee, Joohyung
Title Liquid-Suspended and Liquid-Bridged Liquid Metal Microdroplets [Abstract]
Year 2022
Journal/Proceedings Small
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Abstract Liquid metals (LMs) and alloys are attracting increasing attention owing to their combined advantages of high conductivity and fluidity, and have shown promising results in various emerging applications. Patterning technologies using LMs are being actively researched; among them, direct ink writing is considered a potentially viable approach for efficient LM additive manufacturing. However, true LM additive manufacturing with arbitrary printing geometries remains challenging because of the intrinsically low rheological strength of LMs. Herein, colloidal suspensions of LM droplets amenable to additive manufacturing (or “3D printing”) are realized using formulations containing minute amounts of liquid capillary bridges. The resulting LM suspensions exhibit exceptionally high rheological strength with yield stress values well above 103 Pa, attributed to inter-droplet capillary attraction mediated by the liquid bridges adsorbed on the oxide skin of the LM droplets. Such liquid-bridged LM suspensions, as extrudable ink-type filaments, are based on uncurable continuous-phase liquid media, have a long pot-life and outstanding shear-thinning properties, and shape retention, demonstrating excellent rheological processability suitable for 3D printing. These findings will enable the emergence of a variety of new advanced applications that necessitate LM patterning into highly complicated multidimensional structures.
AUTHOR Nadernezhad, Ali and Groll, Jürgen
Title Machine Learning Reveals a General Understanding of Printability in Formulations Based on Rheology Additives [Abstract]
Year 2022
Journal/Proceedings Advanced Science
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Abstract Hydrogel ink formulations based on rheology additives are becoming increasingly popular as they enable 3-dimensional (3D) printing of non-printable but biologically relevant materials. Despite the widespread use, a generalized understanding of how these hydrogel formulations become printable is still missing, mainly due to their variety and diversity. Employing an interpretable machine learning approach allows the authors to explain the process of rendering printability through bulk rheological indices, with no bias toward the composition of formulations and the type of rheology additives. Based on an extensive library of rheological data and printability scores for 180 different formulations, 13 critical rheological measures that describe the printability of hydrogel formulations, are identified. Using advanced statistical methods, it is demonstrated that even though unique criteria to predict printability on a global scale are highly unlikely, the accretive and collaborative nature of rheological measures provides a qualitative and physically interpretable guideline for designing new printable materials.
AUTHOR Schmieg, Barbara and Gretzinger, Sarah and Schuhmann, Sebastian and Guthausen, Gisela and Hubbuch, Jürgen
Title Magnetic resonance imaging as a tool for quality control in extrusion-based bioprinting [Abstract]
Year 2022
Journal/Proceedings Biotechnology Journal
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Abstract Bioprinting is gaining importance for the manufacturing of tailor-made hydrogel scaffolds in tissue engineering, pharmaceutical research and cell therapy. However, structure fidelity and geometric deviations of printed objects heavily influence mass transport and process reproducibility. Fast, three-dimensional and nondestructive quality control methods will be decisive for the approval in larger studies or industry. Magnetic resonance imaging (MRI) meets these requirements for characterizing heterogeneous soft materials with different properties. Complementary to the idea of decentralized 3D printing, magnetic resonance tomography is common in medicine, and image data processing tools can be transferred system-independently. In this study, a MRI measurement and image analysis protocol was evaluated to jointly assess the reproducibility of three different hydrogels and a reference material. Critical parameters for object quality, namely porosity, hole areas and deviations along the height of the scaffolds are discussed. Geometric deviations could be correlated to specific process parameters, anomalies of the ink or changes of ambient conditions. This strategy allows the systematic investigation of complex 3D objects as well as an implementation as a process control tool. Combined with the monitoring of metadata this approach might pave the way for future industrial applications of 3D printing in the field of biopharmaceutics.
AUTHOR Pai, Roopesh R. and Ajit, Shilpa and Sekar J, Anupama and Nair, Sarath S. and Anil Kumar, P. R. and Velayudhan, Shiny
Title Radical scavenging gelatin methacrylamide based bioink formulation for three dimensional bioprinting of parenchymal liver construct [Abstract]
Year 2022
Journal/Proceedings Bioprinting
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Methacrylated gelatin (GelMA) in the form of methacryloyl, methacrylate, and methacrylamide is an established and widely accepted photocrosslinkable bioink, for three dimensional bioprinting of various tissues. One of the limitations of photocrosslinkable bioinks is the inability to control the free radicals generated by photoinitiators and ultraviolet (UV) rays. The presence of excess free radicals compromises the viability and functionality of cells during crosslinking. In this study, ascorbic acid, a known free radical scavenger (FRS) molecule, was introduced into the GelMA bioink formulation to protect the cell viability, proliferation, and tissue functions of 3D bioprinted parenchymal liver constructs. The concentration of FRS in the bioink was optimized and used for 3D bioprinting of HepG2 cells. The results confirmed that the inclusion of 3.4 mM FRS in the GelMA bioink formulation nullified the excess ROS formed inside the cells. Furthermore, the optimized GelMA formulation containing FRS preserved and improved the cell activity, albumin, and urea synthesis in the 3D construct over 7 days in culture. In the future, this concept could be implemented in the biofabrication of large liver constructs that require multiple or longer durations of UV irradiation.
AUTHOR Demirörs, Ahmet F. and Poloni, Erik and Chiesa, Maddalena and Bargardi, Fabio L. and Binelli, Marco R. and Woigk, Wilhelm and de Castro, Lucas D. C. and Kleger, Nicole and Coulter, Fergal B. and Sicher, Alba and Galinski, Henning and Scheffold, Frank and Studart, André R.
Title Three-dimensional printing of photonic colloidal glasses into objects with isotropic structural color [Abstract]
Year 2022
Journal/Proceedings Nature Communications
Reftype Demirörs2022
DOI/URL DOI
Abstract
Structural color is frequently exploited by living organisms for biological functions and has also been translated into synthetic materials as a more durable and less hazardous alternative to conventional pigments. Additive manufacturing approaches were recently exploited for the fabrication of exquisite photonic objects, but the angle-dependence observed limits a broader application of structural color in synthetic systems. Here, we propose a manufacturing platform for the 3D printing of complex-shaped objects that display isotropic structural color generated from photonic colloidal glasses. Structurally colored objects are printed from aqueous colloidal inks containing monodisperse silica particles, carbon black, and a gel-forming copolymer. Rheology and Small-Angle-X-Ray-Scattering measurements are performed to identify the processing conditions leading to printed objects with tunable structural colors. Multimaterial printing is eventually used to create complex-shaped objects with multiple structural colors using silica and carbon as abundant and sustainable building blocks.
AUTHOR Barceló, Xavier and Eichholz, Kian F. and Garcia, Orquidea and Kelly, Daniel J.
Title Tuning the Degradation Rate of Alginate-Based Bioinks for Bioprinting Functional Cartilage Tissue [Abstract]
Year 2022
Journal/Proceedings Biomedicines
Reftype
DOI/URL URL DOI
Abstract
Negative foreign body responses following the in vivo implantation of bioprinted implants motivate the development of novel bioinks which can rapidly degrade with the formation of functional tissue, whilst still maintaining desired shapes post-printing. Here, we investigated the oxidation of alginate as a means to modify the degradation rate of alginate-based bioinks for cartilage tissue engineering applications. Raw and partially oxidized alginate (OA) were combined at different ratios (Alginate:OA at 100:0; 75:25; 50:50; 25:75; 0:100) to provide finer control over the rate of bioink degradation. These alginate blends were then combined with a temporary viscosity modifier (gelatin) to produce a range of degradable bioinks with rheological properties suitable for extrusion bioprinting. The rate of degradation was found to be highly dependent on the OA content of the bioink. Despite this high mass loss, the initially printed geometry was maintained throughout a 4 week in vitro culture period for all bioink blends except the 0:100 group. All bioink blends also supported robust chondrogenic differentiation of mesenchymal stem/stromal cells (MSCs), resulting in the development of a hyaline-like tissue that was rich in type II collagen and negative for calcific deposits. Such tuneable inks offer numerous benefits to the field of 3D bioprinting, from providing space in a controllable manner for new extracellular matrix deposition, to alleviating concerns associated with a foreign body response to printed material inks in vivo.
AUTHOR Gretzinger, Sarah and Schmieg, Barbara and Guthausen, Gisela and Hubbuch, Jürgen
Title Virtual Reality as Tool for Bioprinting Quality Inspection: A Proof of Principle [Abstract]
Year 2022
Journal/Proceedings Frontiers in Bioengineering and Biotechnology
Reftype
DOI/URL DOI
Abstract
As virtual reality (VR) has drastically evolved over the past few years, the field of applications of VR flourished way beyond the gaming industry. While commercial VR solutions might be available, there is a need to develop a workflow for specific applications. Bioprinting represents such an example. Here, complex 3D data is generated and needs to be visualized in the context of quality control. We demonstrate that the transfer to a commercially available VR software is possible by introducing an optimized workflow. In the present work, we developed a workflow for the visualization of the critical quality attribute (cQA) cell distribution in bioprinted (extrusion-based) samples in VR. The cQA cell distribution is directly influenced by the pre-processing step mixing of cell material in the bioink. Magnetic Resonance Imaging (MRI) was used as an analytical tool to generate spatially resolved 2.5 and 3D data of the bioprinted objects. A sample with poor quality in respect of the cQA cell distribution was identified as its inhomogeneous cell distribution could be displayed spatially resolved in VR. The described workflow facilitates the usage of VR as a tool for quality inspection in the field of bioprinting and represents a powerful tool for visualization of complex 3D MRI data.
AUTHOR Cernencu, Alexandra I. and Lungu, Adriana and Dragusin, Diana M. and Stancu, Izabela C. and Dinescu, Sorina and Balahura, Liliana R. and Mereuta, Paul and Costache, Marieta and Iovu, Horia
Title 3D Bioprinting of Biosynthetic Nanocellulose-Filled GelMA Inks Highly Reliable for Soft Tissue-Oriented Constructs [Abstract]
Year 2021
Journal/Proceedings Materials
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DOI/URL URL DOI
Abstract
Bioink-formulations based on gelatin methacrylate combined with oxidized cellulose nanofibrils are employed in the present study. The parallel investigation of the printing performance, morphological, swelling, and biological properties of the newly developed hydrogels was performed, with inks prepared using methacrylamide-modified gelatins of fish or bovine origin. Scaffolds with versatile and well-defined internal structure and high shape fidelity were successfully printed due to the high viscosity and shear-thinning behavior of formulated inks and then photo-crosslinked. The biocompatibility of 3D-scaffolds was surveyed using human adipose stem cells (hASCs) and high viability and proliferation rates were obtained when in contact with the biomaterial. Furthermore, bioprinting tests were performed with hASCs embedded in the developed formulations. The results demonstrated that the designed inks are a versatile toolkit for 3D bioprinting and further show the benefits of using fish-derived gelatin for biofabrication.
AUTHOR Rößler, Sina and Brückner, Andreas and Kruppke, Iris and Wiesmann, Hans-Peter and Hanke, Thomas and Kruppke, Benjamin
Title 3D Plotting of Silica/Collagen Xerogel Granules in an Alginate Matrix for Tissue-Engineered Bone Implants [Abstract]
Year 2021
Journal/Proceedings Materials
Reftype
DOI/URL URL DOI
Abstract
Today, materials designed for bone regeneration are requested to be degradable and resorbable, bioactive, porous, and osteoconductive, as well as to be an active player in the bone-remodeling process. Multiphasic silica/collagen Xerogels were shown, earlier, to meet these requirements. The aim of the present study was to use these excellent material properties of silica/collagen Xerogels and to process them by additive manufacturing, in this case 3D plotting, to generate implants matching patient specific shapes of fractures or lesions. The concept is to have Xerogel granules as active major components embedded, to a large proportion, in a matrix that binds the granules in the scaffold. By using viscoelastic alginate as matrix, pastes of Xerogel granules were processed via 3D plotting. Moreover, alginate concentration was shown to be the key to a high content of irregularly shaped Xerogel granules embedded in a minimum of matrix phase. Both the alginate matrix and Xerogel granules were also shown to influence viscoelastic behavior of the paste, as well as the dimensionally stability of the scaffolds. In conclusion, 3D plotting of Xerogel granules was successfully established by using viscoelastic properties of alginate as matrix phase.
AUTHOR Leu Alexa, Rebeca and Ianchis, Raluca and Savu, Diana and Temelie, Mihaela and Trica, Bogdan and Serafim, Andrada and Vlasceanu, George Mihail and Alexandrescu, Elvira and Preda, Silviu and Iovu, Horia
Title 3D Printing of Alginate-Natural Clay Hydrogel-Based Nanocomposites [Abstract]
Year 2021
Journal/Proceedings Gels
Reftype
DOI/URL URL DOI
Abstract
Biocompatibility, biodegradability, shear tinning behavior, quick gelation and an easy crosslinking process makes alginate one of the most studied polysaccharides in the field of regenerative medicine. The main purpose of this study was to obtain tissue-like materials suitable for use in bone regeneration. In this respect, alginate and several types of clay were investigated as components of 3D-printing, nanocomposite inks. Using the extrusion-based nozzle, the nanocomposites inks were printed to obtain 3D multilayered scaffolds. To observe the behavior induced by each type of clay on alginate-based inks, rheology studies were performed on composite inks. The structure of the nanocomposites samples was examined using Fourier Transform Infrared Spectrometry and X-ray Diffraction (XRD), while the morphology of the 3D-printed scaffolds was evaluated using Electron Microscopy (SEM, TEM) and Micro-Computed Tomography (Micro-CT). The swelling and dissolvability of each composite scaffold in phosfate buffer solution were followed as function of time. Biological studies indicated that the cells grew in the presence of the alginate sample containing unmodified clay, and were able to proliferate and generate calcium deposits in MG-63 cells in the absence of specific signaling molecules. This study provides novel information on potential manufacturing methods for obtaining nanocomposite hydrogels suitable for 3D printing processes, as well as valuable information on the clay type selection for enabling accurate 3D-printed constructs. Moreover, this study constitutes the first comprehensive report related to the screening of several natural clays for the additive manufacturing of 3D constructs designed for bone reconstruction therapy.
AUTHOR Leu Alexa, Rebeca and Iovu, Horia and Ghitman, Jana and Serafim, Andrada and Stavarache, Cristina and Marin, Maria-Minodora and Ianchis, Raluca
Title 3D-Printed Gelatin Methacryloyl-Based Scaffolds with Potential Application in Tissue Engineering [Abstract]
Year 2021
Journal/Proceedings Polymers
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DOI/URL URL DOI
Abstract
The development of materials for 3D printing adapted for tissue engineering represents one of the main concerns nowadays. Our aim was to obtain suitable 3D-printed scaffolds based on methacrylated gelatin (GelMA). In this respect, three degrees of GelMA methacrylation, three different concentrations of GelMA (10%, 20%, and 30%), and also two concentrations of photoinitiator (I-2959) (0.5% and 1%) were explored to develop proper GelMA hydrogel ink formulations to be used in the 3D printing process. Afterward, all these GelMA hydrogel-based inks/3D-printed scaffolds were characterized structurally, mechanically, and morphologically. The presence of methacryloyl groups bounded to the surface of GelMA was confirmed by FTIR and 1H-NMR analyses. The methacrylation degree influenced the value of the isoelectric point that decreased with the GelMA methacrylation degree. A greater concentration of photoinitiator influenced the hydrophilicity of the polymer as proved using contact angle and swelling studies because of the new bonds resulting after the photocrosslinking stage. According to the mechanical tests, better mechanical properties were obtained in the presence of the 1% initiator. Circular dichroism analyses demonstrated that the secondary structure of gelatin remained unaffected during the methacrylation process, thus being suitable for biological applications.
AUTHOR Jiahui Lai and Xinliang Ye and Jia Liu and Chong Wang and Junzhi Li and Xiang Wang and Mingze Ma and Min Wang
Title 4D printing of highly printable and shape morphing hydrogels composed of alginate and methylcellulose [Abstract]
Year 2021
Journal/Proceedings Materials & Design
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DOI/URL URL DOI
Abstract
4D printing of swellable/shrinkable hydrogels has been viewed as an appealing approach for fabricating dynamic structures for various biomedical applications. However, 4D printing of precise hydrogel structures is still highly challenging due to the relatively poor printability of hydrogels and high surface roughness of printed patterns, when micro extrusion-based 3D printers are used. In this study, a highly printable and shape morphing hydrogel was investigated for 4D printing by blending alginate (Alg) and methylcellulose (MC). The optimized Alg/MC hydrogel exhibited excellent rheological properties, extrudability and shape fidelity of printed structures. The printable Alg/MC hydrogel was 4D printed into a series of patterned 2D architectures which were encoded with anisotropic stiffness and swelling behaviors by strategically controlling the network density gradients vertical to the orientation of the patterned strips. By controlling the strip interspacing and angle, these 2D architectures could transform into various prescribed simple 3D morphologies (e.g., tube-curling and helix) and complex 3D morphologies (e.g., double helix and flowers) after immersion in a calcium chloride solution. This shape morphing Alg/MC hydrogel with excellent printability has high potential for 4D printing of delicate hydrogel patterns, which are increasingly needed in the tissue engineering, biomedical device and soft robotics fields.
AUTHOR Kwak, Chaesu and Young Ryu, Seoung and Park, Hyunsu and Lim, Sehyeong and Yang, Jeewon and Kim, Jieun and Hyung Kim, Jin and Lee, Joohyung
Title A pickering emulsion stabilized by chlorella microalgae as an eco-friendly extrusion-based 3D printing ink processable under ambient conditions [Abstract]
Year 2021
Journal/Proceedings Journal of Colloid and Interface Science
Reftype
DOI/URL URL DOI
Abstract
Three-dimensional (3D) printing technology is actively utilized in various industrial fields because it facilitates effective and customizable fabrication of complex structures. An important processing route for 3D printing is the extrusion of inks in the form of colloidal suspensions or emulsions, which has recently attracted considerable attention because it allows for selection of a wide range of printing materials and is operable under ambient processing conditions. Herein, we investigate the 3D printability of complex fluids containing chlorella microalgae as an eco-friendly material for 3D printing. Two possible ink types are considered: aqueous chlorella suspensions and emulsions of oil and water mixtures. While the aqueous chlorella suspensions at high particle loading display the 3D-printable rheological properties such as high yield stress and good shape retention, the final structures after extruding and drying the suspensions under ambient conditions show a significant number of macroscopic defects, limiting their practical application. In contrast, the 3D structures produced from the oil-in-water Pickering emulsions stabilized by chlorella microalgae, which are amphiphilic and active at the oil–water interface, show significantly reduced defect formation. Addition of a fast-evaporable oil phase, hexane, is crucial in the mechanisms of enhanced cementation between the individual microalgae via increased inter-particle packing, capillary attraction, and hydrophobic interaction. Furthermore, addition of solid paraffin wax, which is crystalline but well-soluble in the hydrocarbon oil phase under ambient conditions, completely eliminates the undesirable defect formation via enhanced inter-particle binding, while maintaining the overall rheological properties of the emulsion. The optimal formulation of the Pickering emulsion is finally employed to produce a 3D scaffold of satisfactory structural integrity, suggesting that the chlorella-based ink, in the form of an emulsion, has potential as an eco-friendly 3D printing ink processable under ambient conditions.
AUTHOR Zuoxin Zhou and Mario Samperi and Lea Santu and Glenieliz Dizon and Shereen Aboarkaba and David Limón and David Limón and Christopher Tuck and Lluïsa Pérez-García and Derek J. Irvine and David B. Amabilino and Ricky Wildman
Title An Imidazolium-Based Supramolecular Gelator Enhancing Interlayer Adhesion in 3D Printed Dual Network Hydrogels [Abstract]
Year 2021
Journal/Proceedings Materials & Design
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DOI/URL URL DOI
Abstract
The variety of UV-curable monomers for 3D printing is limited by a requirement for rapid curing after each sweep depositing a layer. This study proposes to trigger supramolecular self-assembly during the process by a gemini imidazolium-based low-molecular-weight gelator, allowing printing of certain monomers. The as-printed hydrogel structures were supported by a gelator network immobilising monomer:water solutions. A thixotropic hydrogel was formed with a recovery time of < 50 seconds, storage modulus = 8.1 kPa and yield stress = 18 Pa, processable using material-extrusion 3D printing. Material-extrusion 3D printed objects are usually highly anisotropic, but in this case the gelator network improved the isotropy by subverting the usual layer-by-layer curing strategy. The monomer in all printed layers was cured simultaneously during post-processing to form a continuous polymeric network. The two networks then physically interpenetrate to enhance mechanical performance. The double-network hydrogels fabricated with layers cured simultaneously showed 62-147 % increases in tensile properties compared to layer-by-layer cured hydrogels. The results demonstrated excellent inter- and intra-layered coalescence. Consequently, the tensile properties of 3D printed hydrogels were close to mould cast objects. This study has demonstrated the benefits of using gelators to expand the variety of 3D printable monomers and shown improved isotropy to offer excellent mechanical performances.
AUTHOR Yuanhao Wu and Gabriele Maria Fortunato and Babatunde O Okesola and Francesco Luigi Pellerej di Brocchetti and Ratima Suntornnond and John Connelly and Carmelo De Maria and Jose Carlos Rodriguez-Cabello and Giovanni Vozzi and Wen Wang and Alvaro Mata
Title An interfacial self-assembling bioink for the manufacturing of capillary-like structures with tuneable and anisotropic permeability [Abstract]
Year 2021
Journal/Proceedings Biofabrication
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DOI/URL DOI
Abstract
Self-assembling bioinks offer the possibility to biofabricate with molecular precision, hierarchical control, and biofunctionality. For this to become a reality with widespread impact, it is essential to engineer these ink systems ensuring reproducibility and providing suitable standardization. We have reported a self-assembling bioink based on disorder-to-order transitions of an elastin-like recombinamer (ELR) to co-assemble with graphene oxide (GO). Here, we establish reproducible processes, optimize printing parameters for its use as a bioink, describe new advantages that the self-assembling bioink can provide, and demonstrate how to fabricate novel structures with physiological relevance. We fabricate capillary-like structures with resolutions down to ∼10 µm in diameter and ∼2 µm thick tube walls and use both experimental and finite element analysis to characterize the printing conditions, underlying interfacial diffusion-reaction mechanism of assembly, printing fidelity, and material porosity and permeability. We demonstrate the capacity to modulate the pore size and tune the permeability of the resulting structures with and without human umbilical vascular endothelial cells. Finally, the potential of the ELR-GO bioink to enable supramolecular fabrication of biomimetic structures was demonstrated by printing tubes exhibiting walls with progressively different structure and permeability.
AUTHOR Leu Alexa, Rebeca and Iovu, Horia and Trica, Bogdan and Zaharia, Catalin and Serafim, Andrada and Alexandrescu, Elvira and Radu, Ionut-Cristian and Vlasceanu, George and Preda, Silviu and Ninciuleanu, Claudia Mihaela and Ianchis, Raluca
Title Assessment of Naturally Sourced Mineral Clays for the 3D Printing of Biopolymer-Based Nanocomposite Inks [Abstract]
Year 2021
Journal/Proceedings Nanomaterials
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DOI/URL URL DOI
Abstract
The present study investigated the possibility of obtaining 3D printed composite constructs using biomaterial-based nanocomposite inks. The biopolymeric matrix consisted of methacrylated gelatin (GelMA). Several types of nanoclay were added as the inorganic component. Our aim was to investigate the influence of clay type on the rheological behavior of ink formulations and to determine the morphological and structural properties of the resulting crosslinked hydrogel-based nanomaterials. Moreover, through the inclusion of nanoclays, our goal was to improve the printability and shape fidelity of nanocomposite scaffolds. The viscosity of all ink formulations was greater in the presence of inorganic nanoparticles as shear thinning occurred with increased shear rate. Hydrogel nanocomposites presented predominantly elastic rather than viscous behavior as the materials were crosslinked which led to improved mechanical properties. The inclusion of nanoclays in the biopolymeric matrix limited hydrogel swelling due the physical barrier effect but also because of the supplementary crosslinks induced by the clay layers. The distribution of inorganic filler within the GelMA-based hydrogels led to higher porosities as a consequence of their interaction with the biopolymeric ink. The present study could be useful for the development of soft nanomaterials foreseen for the additive manufacturing of customized implants for tissue engineering.
AUTHOR Silvestri, Alessandro and Criado, Alejandro and Poletti, Fabrizio and Wang, Faxing and Fanjul-Bolado, Pablo and González-García, María B. and García-Astrain, Clara and Liz-Marzán, Luis M. and Feng, Xinliang and Zanardi, Chiara and Prato, Maurizio
Title Bioresponsive, Electroactive, and Inkjet-Printable Graphene-Based Inks [Abstract]
Year 2021
Journal/Proceedings Advanced Functional Materials
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DOI/URL DOI
Abstract
Abstract With the advent of flexible electronics, the old fashioned and conventional solid-state technology will be replaced by conductive inks combined with low-cost printing techniques. Graphene is an ideal candidate to produce conductive inks, due to its excellent conductivity and zero bandgap. The possibility to chemically modify graphene with active molecules opens up the field of responsive conductive inks. Herein, a bioresponsive, electroactive, and inkjet-printable graphene ink is presented. The ink is based on graphene chemically modified with selected enzymes and an electrochemical mediator, to transduce the products of the enzymatic reaction into an electron flow, proportional to the analyte concentration. A water-based formulation is engineered to be respectful with the enzymatic activity while matching the stringent requirements of inkjet printing. The efficient electrochemical performance of the ink, as well as a proof-of-concept application in biosensing, is demonstrated. The versatility of the system is demonstrated by modifying graphene with various oxidoreductases, obtaining inks with selectivity toward glucose, lactate, methanol, and ethanol.
AUTHOR Kamdem Tamo, Arnaud and Doench, Ingo and Walter, Lukas and Montembault, Alexandra and Sudre, Guillaume and David, Laurent and Morales-Helguera, Aliuska and Selig, Mischa and Rolauffs, Bernd and Bernstein, Anke and Hoenders, Daniel and Walther, Andreas and Osorio-Madrazo, Anayancy
Title Development of Bioinspired Functional Chitosan/Cellulose Nanofiber 3D Hydrogel Constructs by 3D Printing for Application in the Engineering of Mechanically Demanding Tissues [Abstract]
Year 2021
Journal/Proceedings Polymers
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DOI/URL DOI
Abstract
Soft tissues are commonly fiber-reinforced hydrogel composite structures, distinguishable from hard tissues by their low mineral and high water content. In this work, we proposed the development of 3D printed hydrogel constructs of the biopolymers chitosan (CHI) and cellulose nanofibers (CNFs), both without any chemical modification, which processing did not incorporate any chemical crosslinking. The unique mechanical properties of native cellulose nanofibers offer new strategies for the design of environmentally friendly high mechanical performance composites. In the here proposed 3D printed bioinspired CNF-filled CHI hydrogel biomaterials, the chitosan serves as a biocompatible matrix promoting cell growth with balanced hydrophilic properties, while the CNFs provide mechanical reinforcement to the CHI-based hydrogel. By means of extrusion-based printing (EBB), the design and development of 3D functional hydrogel scaffolds was achieved by using low concentrations of chitosan (2.0–3.0% (w/v)) and cellulose nanofibers (0.2–0.4% (w/v)). CHI/CNF printed hydrogels with good mechanical performance (Young’s modulus 3.0 MPa, stress at break 1.5 MPa, and strain at break 75%), anisotropic microstructure and suitable biological response, were achieved. The CHI/CNF composition and processing parameters were optimized in terms of 3D printability, resolution, and quality of the constructs (microstructure and mechanical properties), resulting in good cell viability. This work allows expanding the library of the so far used biopolymer compositions for 3D printing of mechanically performant hydrogel constructs, purely based in the natural polymers chitosan and cellulose, offering new perspectives in the engineering of mechanically demanding hydrogel tissues like intervertebral disc (IVD), cartilage, meniscus, among others.
AUTHOR Curti, Filis and Drăgușin, Diana-Maria and Serafim, Andrada and Iovu, Horia and Stancu, Izabela-Cristina
Title Development of thick paste-like inks based on superconcentrated gelatin/alginate for 3D printing of scaffolds with shape fidelity and stability [Abstract]
Year 2021
Journal/Proceedings Materials Science and Engineering: C
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DOI/URL URL DOI
Abstract
Shape fidelity and integrity are serious challenges in the 3D printing of hydrogel precursors, as they can influence the overall performance of 3D scaffolds. This work reports the development of superconcentrated inks based on sodium alginate and fish gelatin as an appealing strategy to satisfy such challenges and dictate the quality of the printed scaffolds, without using crosslinking strategies during 3D printing. SEM micrographs and micro-CT images indicate the homogeneous distribution of the polysaccharide in the gelatin-based matrix, suggesting its potential to act as a reinforcing additive. The high concentration of gelatin aqueous solution (50 wt%) and substantial incorporation of alginate have facilitated the highly accurate printability and influence the in vitro stability and mechanical properties of the printed scaffolds. An improvement of the stiffness is dictated by the increase of alginate concentration from 20 wt% to 25 wt%, and an increase of Young modulus with about 46% is reached, confirming the reinforcing effect of polysaccharide. This study highlights the potential of paste-type inks to provide high resolution 3D printed structures with appealing structural and dimensional stability, in vitro degradability and mechanical properties for biomedical applications.
AUTHOR Shiwarski,Daniel J. and Hudson,Andrew R. and Tashman,Joshua W. and Feinberg,Adam W.
Title Emergence of FRESH 3D printing as a platform for advanced tissue biofabrication
Year 2021
Journal/Proceedings APL Bioengineering
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DOI/URL DOI
AUTHOR Chen, Shengyang and Shi, Qian and Jang, Taesik and Ibrahim, Mohammed Shahrudin Bin and Deng, Jingyu and Ferracci, Gaia and Tan, Wen See and Cho, Nam-Joon and Song, Juha
Title Engineering Natural Pollen Grains as Multifunctional 3D Printing Materials [Abstract]
Year 2021
Journal/Proceedings Advanced Functional Materials
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DOI/URL DOI
Abstract
Abstract The development of multifunctional 3D printing materials from sustainable natural resources is a high priority in additive manufacturing. Using an eco-friendly method to transform hard pollen grains into stimulus-responsive microgel particles, we engineered a pollen-derived microgel suspension that can serve as a functional reinforcement for composite hydrogel inks and as a supporting matrix for versatile freeform 3D printing systems. The pollen microgel particles enabled the printing of composite inks and improved the mechanical and physiological stabilities of alginate and hyaluronic acid hydrogel scaffolds for 3D cell culture applications. Moreover, the particles endowed the inks with stimulus-responsive controlled release properties. The suitability of the pollen microgel suspension as a supporting matrix for freeform 3D printing of alginate and silicone rubber inks was demonstrated and optimized by tuning the rheological properties of the microgel. Compared with other classes of natural materials, pollen grains have several compelling features, including natural abundance, renewability, affordability, processing ease, monodispersity, and tunable rheological features, which make them attractive candidates to engineer advanced materials for 3D printing applications.
AUTHOR Götz, Lisa-Marie and Holeczek, Katharina and Groll, Jürgen and Jüngst, Tomasz and Gbureck, Uwe
Title Extrusion-Based 3D Printing of Calcium Magnesium Phosphate Cement Pastes for Degradable Bone Implants [Abstract]
Year 2021
Journal/Proceedings Materials
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DOI/URL URL DOI
Abstract
This study aimed to develop printable calcium magnesium phosphate pastes that harden by immersion in ammonium phosphate solution post-printing. Besides the main mineral compound, biocompatible ceramic, magnesium oxide and hydroxypropylmethylcellulose (HPMC) were the crucial components. Two pastes with different powder to liquid ratios of 1.35 g/mL and 1.93 g/mL were characterized regarding their rheological properties. Here, ageing over the course of 24 h showed an increase in viscosity and extrusion force, which was attributed to structural changes in HPMC as well as the formation of magnesium hydroxide by hydration of MgO. The pastes enabled printing of porous scaffolds with good dimensional stability and enabled a setting reaction to struvite when immersed in ammonium phosphate solution. Mechanical performance under compression was approx. 8–20 MPa as a monolithic structure and 1.6–3.0 MPa for printed macroporous scaffolds, depending on parameters such as powder to liquid ratio, ageing time, strand thickness and distance.
AUTHOR Wibowo, Arie and Tajalla, Gusti U. N. and Marsudi, Maradhana A. and Cooper, Glen and Asri, Lia A.T.W. and Liu, Fengyuan and Ardy, Husaini and Bartolo, Paulo J.D.S.
Title Green Synthesis of Silver Nanoparticles Using Extract of Cilembu Sweet Potatoes (Ipomoea batatas L var. Rancing) as Potential Filler for 3D Printed Electroactive and Anti-Infection Scaffolds [Abstract]
Year 2021
Journal/Proceedings Molecules
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DOI/URL URL DOI
Abstract
Electroactive biomaterials are fascinating for tissue engineering applications because of their ability to deliver electrical stimulation directly to cells, tissue, and organs. One particularly attractive conductive filler for electroactive biomaterials is silver nanoparticles (AgNPs) because of their high conductivity, antibacterial activity, and ability to promote bone healing. However, production of AgNPs involves a toxic reducing agent which would inhibit biological scaffold performance. This work explores facile and green synthesis of AgNPs using extract of Cilembu sweet potato and studies the effect of baking and precursor concentrations (1, 10 and 100 mM) on AgNPs’ properties. Transmission electron microscope (TEM) results revealed that the smallest particle size of AgNPs (9.95 ± 3.69 nm) with nodular morphology was obtained by utilization of baked extract and ten mM AgNO3. Polycaprolactone (PCL)/AgNPs scaffolds exhibited several enhancements compared to PCL scaffolds. Compressive strength was six times greater (3.88 ± 0.42 MPa), more hydrophilic (contact angle of 76.8 ± 1.7°), conductive (2.3 ± 0.5 × 10−3 S/cm) and exhibited anti-bacterial properties against Staphylococcus aureus ATCC3658 (99.5% reduction of surviving bacteria). Despite the promising results, further investigation on biological assessment is required to obtain comprehensive study of this scaffold. This green synthesis approach together with the use of 3D printing opens a new route to manufacture AgNPs-based electroactive with improved anti-bacterial properties without utilization of any toxic organic solvents.
AUTHOR Tan, Edgar Y. S. and Suntornnond, Ratima and Yeong, Wai Yee
Title High-Resolution Novel Indirect Bioprinting of Low-Viscosity Cell-Laden Hydrogels via Model-Support Bioink Interaction [Abstract]
Year 2021
Journal/Proceedings 3D Printing and Additive Manufacturing
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DOI/URL DOI
Abstract
Abstract Bioprinting of unmodified soft extracellular matrix into complex 3D structures has remained challenging to fabricate. Herein, we established a novel process for the printing of low-viscosity hydrogel by using a unique support technique to retain the structural integrity of the support structure. We demonstrated that this process of printing could be used for different types of hydrogel, ranging from fast crosslinking gelatin methacrylate to slow crosslinking collagen type I. In addition, we evaluated the biocompatibility of the process by observing the effects of the cytotoxicity of L929 and the functionality of the human umbilical vein endothelium primary cells after printing. The results show that the bioprinted construct provided excellent biocompatibility as well as supported cell growth and differentiation. Thus, this is a novel technique that can be potentially used to enhance the resolution of the extrusion-based bioprinter.
AUTHOR Lechner, Annika and Trossmann, Vanessa T. and Scheibel, Thomas
Title Impact of Cell Loading of Recombinant Spider Silk Based Bioinks on Gelation and Printability [Abstract]
Year 2021
Journal/Proceedings Macromolecular Bioscience
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DOI/URL DOI
Abstract
Abstract Printability of bioinks encompasses considerations concerning rheology and extrudability, characterization of filament formation, shape fidelity, cell viability and post-printing cellular development. Recombinant spider silk based hydrogels might be a suitable material to be used in bioinks, i.e. a formulation of cells and materials to be used for bioprinting. Here, the high shape fidelity of spider silk ink is shown by bioprinting the shape and size of a human aortic valve. Further the influence of the encapsulation of cells has been evaluated on spider silk hydrogel formation, hydrogel mechanics, and shape fidelity upon extrusion based bioprinting. It is shown that the presence of cells impacts gelation of spider silk proteins differently depending on the used silk variant. RGD-modified spider silk hydrogels are physically crosslinked by the cells, while there is no active interaction between cells and un-tagged spider silk proteins. Strikingly, even at cell densities up to ten million cells/ml, cell viability is high after extrusion based printing which is a significant prerequisite for future applications. Shape fidelity of the printed constructs is demonstrated using a filament collapse test in absence and presence of human cells. This article is protected by copyright. All rights reserved
AUTHOR Trucco, Diego and Sharma, Aarushi and Manferdini, Cristina and Gabusi, Elena and Petretta, Mauro and Desando, Giovanna and Ricotti, Leonardo and Chakraborty, Juhi and Ghosh, Sourabh and Lisignoli, Gina
Title Modeling and Fabrication of Silk Fibroin-Gelatin-Based Constructs Using Extrusion-Based Three-Dimensional Bioprinting [Abstract]
Year 2021
Journal/Proceedings ACS Biomater. Sci. Eng.
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DOI/URL DOI
Abstract
Robotic dispensing-based 3D bioprinting represents one of the most powerful technologies to develop hydrogel-based 3D constructs with enormous potential in the field of regenerative medicine. The optimization of hydrogel printing parameters, proper geometry and internal architecture of the constructs, and good cell viability during the bioprinting process are the essential requirements. In this paper, an analytical model based on the hydrogel rheological properties was developed to predict the extruded filament width in order to maximize the printed structure’s fidelity to the design. Viscosity data of two natural hydrogels were imputed to a power-law model to extrapolate the filament width. Further, the model data were validated by monitoring the obtained filament width as the output. Shear stress values occurring during the bioprinting process were also estimated. Human mesenchymal stromal cells (hMSCs) were encapsulated in the silk fibroin-gelatin (G)-based hydrogel, and a 3D bioprinting process was performed to produce cell-laden constructs. Live and dead assay allowed estimating the impact of needle shear stress on cell viability after the bioprinting process. Finally, we tested the potential of hMSCs to undergo chondrogenic differentiation by evaluating the cartilaginous extracellular matrix production through immunohistochemical analyses. Overall, the use of the proposed analytical model enables defining the optimal printing parameters to maximize the fabricated constructs’ fidelity to design parameters before the process execution, enabling to achieve more controlled and standardized products than classical trial-and-error approaches in the biofabrication of engineered constructs. Employing modeling systems exploiting the rheological properties of the hydrogels might be a valid tool in the future for guaranteeing high cell viability and for optimizing tissue engineering approaches in regenerative medicine applications. Robotic dispensing-based 3D bioprinting represents one of the most powerful technologies to develop hydrogel-based 3D constructs with enormous potential in the field of regenerative medicine. The optimization of hydrogel printing parameters, proper geometry and internal architecture of the constructs, and good cell viability during the bioprinting process are the essential requirements. In this paper, an analytical model based on the hydrogel rheological properties was developed to predict the extruded filament width in order to maximize the printed structure’s fidelity to the design. Viscosity data of two natural hydrogels were imputed to a power-law model to extrapolate the filament width. Further, the model data were validated by monitoring the obtained filament width as the output. Shear stress values occurring during the bioprinting process were also estimated. Human mesenchymal stromal cells (hMSCs) were encapsulated in the silk fibroin-gelatin (G)-based hydrogel, and a 3D bioprinting process was performed to produce cell-laden constructs. Live and dead assay allowed estimating the impact of needle shear stress on cell viability after the bioprinting process. Finally, we tested the potential of hMSCs to undergo chondrogenic differentiation by evaluating the cartilaginous extracellular matrix production through immunohistochemical analyses. Overall, the use of the proposed analytical model enables defining the optimal printing parameters to maximize the fabricated constructs’ fidelity to design parameters before the process execution, enabling to achieve more controlled and standardized products than classical trial-and-error approaches in the biofabrication of engineered constructs. Employing modeling systems exploiting the rheological properties of the hydrogels might be a valid tool in the future for guaranteeing high cell viability and for optimizing tissue engineering approaches in regenerative medicine applications.
AUTHOR Iria Seoane-Viaño and Patricija Januskaite and Carmen Alvarez-Lorenzo and Abdul W. Basit and Alvaro Goyanes
Title Semi-solid extrusion 3D printing in drug delivery and biomedicine: Personalised solutions for healthcare challenges [Abstract]
Year 2021
Journal/Proceedings Journal of Controlled Release
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Abstract
Three-dimensional (3D) printing is an innovative additive manufacturing technology, capable of fabricating unique structures in a layer-by-layer manner. Semi-solid extrusion (SSE) is a subset of material extrusion 3D printing, and through the sequential deposition of layers of gel or paste creates objects of any desired size and shape. In comparison to other extrusion-based technologies, SSE 3D printing employs low printing temperatures which makes it suitable for drug delivery and biomedical applications, and the use of disposable syringes provides benefits in meeting critical quality requirements for pharmaceutical use. Besides pharmaceutical manufacturing, SSE 3D printing has attracted increasing attention in the field of bioelectronics, particularly in the manufacture of biosensors capable of measuring physiological parameters or as a means to trigger drug release from medical devices. This review begins by highlighting the major printing process parameters and material properties that influence the feasibility of transforming a 3D design into a 3D object, and follows with a discussion on the current SSE 3D printing developments and their applications in the fields of pharmaceutics, bioprinting and bioelectronics. Finally, the advantages and limitations of this technology are explored, before focusing on its potential clinical applications and suitability for preparing personalised medicines.
AUTHOR Göckler, Tobias and Haase, Sonja and Kempter, Xenia and Pfister, Rebecca and Maciel, Bruna R. and Grimm, Alisa and Molitor, Tamara and Willenbacher, Norbert and Schepers, Ute
Title Tuning Superfast Curing Thiol-Norbornene-Functionalized Gelatin Hydrogels for 3D Bioprinting [Abstract]
Year 2021
Journal/Proceedings Advanced Healthcare Materials
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Abstract
Abstract Photocurable gelatin-based hydrogels have established themselves as powerful bioinks in tissue engineering due to their excellent biocompatibility, biodegradability, light responsiveness, thermosensitivity and bioprinting properties. While gelatin methacryloyl (GelMA) has been the gold standard for many years, thiol-ene hydrogel systems based on norbornene-functionalized gelatin (GelNB) and a thiolated crosslinker have recently gained increasing importance. In this paper, a highly reproducible water-based synthesis of GelNB is presented, avoiding the use of dimethyl sulfoxide (DMSO) as organic solvent and covering a broad range of degrees of functionalization (DoF: 20% to 97%). Mixing with thiolated gelatin (GelS) results in the superfast curing photoclick hydrogel GelNB/GelS. Its superior properties over GelMA, such as substantially reduced amounts of photoinitiator (0.03% (w/v)), superfast curing (1–2 s), higher network homogeneity, post-polymerization functionalization ability, minimal cross-reactivity with cellular components, and improved biocompatibility of hydrogel precursors and degradation products lead to increased survival of primary cells in 3D bioprinting. Post-printing viability analysis revealed excellent survival rates of > 84% for GelNB/GelS bioinks of varying crosslinking density, while cell survival for GelMA bioinks is strongly dependent on the DoF. Hence, the semisynthetic and easily accessible GelNB/GelS hydrogel is a highly promising bioink for future medical applications and other light-based biofabrication techniques.
AUTHOR Chen, Shengyang and Jang, Tae-Sik and Pan, Houwen Matthew and Jung, Hyun-Do and Sia, Ming Wei and Xie, Shuying and Hang, Yao and Chong, Seow and Wong, Dongan
Title 3D Freeform Printing of Nanocomposite Hydrogels through in situ Precipitation in Reactive Viscous Fluid
Year 2020
Journal/Proceedings International Journal of Bioprinting
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AUTHOR Rupp, Harald and Binder, Wolfgang H.
Title 3D Printing of Core–Shell Capsule Composites for Post-Reactive and Damage Sensing Applications [Abstract]
Year 2020
Journal/Proceedings Advanced Materials Technologies
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Abstract 3D printing of multicomponent materials as an advantageous method over traditional mold casting methods is demonstrated, developing small core–shell capsule composites fabricated by a two-step 3D printing process. Using a two-print-head system (fused deposition modeling extruder and a liquid inkjet print head), micro-sized capsules are manufactured in sizes ranging from 100 to 800 µm. The thermoplastic polymer poly(ε-caprolactone) (PCL) is chosen as matrix/shell material due to its optimal interaction with the embedded hydrophobic liquids. First, the core–shell capsules are printed with model liquids and pure PCL to optimize the printing parameters and to ensure fully enclosed capsules inside the polymer. As a proof of concept, novel “click” reaction systems, used in self-healing and stress-detection applications, are manufactured in which PCL composites with nano- and micro-fillers are combined with reactive, encapsulated liquids. The so generated 3D printed core–shell capsule composite can be used for post-printing reactions and damage sensing when combined with a fluorogenic dye.
AUTHOR Jung, Harry and Lee, Ji Seung and Lee, Jun Ho and Park, Ki Joon and Lee, Jae Jun and Park, Hae Sang
Title A Feasibility Study for 3D-printed Poly(methyl methacrylate)-resin Tracheostomy Tube Using a Hamster Cheek Pouch Model
Year 2020
Journal/Proceedings In Vivo
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AUTHOR Lee, J. M. and Sing, S. L. and Yeong, W. Y.
Title Bioprinting of Multimaterials with Computer-aided Design/Computer -aided Manufacturing [Abstract]
Year 2020
Journal/Proceedings International Journal of Bioprinting; Vol 6, No 1 (2020)
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Multimaterials deposition, a distinct advantage in bioprinting, overcomes material’s limitation in hydrogel-based bioprinting. Multimaterials are deposited in a build/support configuration to improve the structural integrity of three-dimensional bioprinted construct. A combination of rapid cross-linking hydrogel has been chosen for the build/support setup. The bioprinted construct was further chemically cross-linked to ensure a stable construct after print. This paper also proposes a file segmentation and preparation technique to be used in bioprinting for printing freeform structures.
AUTHOR Müller, Michael and Fisch, Philipp and Molnar, Marc and Eggert, Sebastian and Binelli, Marco and Maniura-Weber, Katharina and Zenobi-Wong, Marcy
Title Development and thorough characterization of the processing steps of an ink for 3D printing for bone tissue engineering [Abstract]
Year 2020
Journal/Proceedings Materials Science and Engineering: C
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Abstract
Achieving reproducibility in the 3D printing of biomaterials requires a robust polymer synthesis method to reduce batch-to-batch variation as well as methods to assure a thorough characterization throughout the manufacturing process. Particularly biomaterial inks containing large solid fractions such as ceramic particles, often required for bone tissue engineering applications, are prone to inhomogeneity originating from inadequate mixing or particle aggregation which can lead to inconsistent printing results. The production of such an ink for bone tissue engineering consisting of gellan gum methacrylate (GG-MA), hyaluronic acid methacrylate and hydroxyapatite (HAp) particles was therefore optimized in terms of GG-MA synthesis and ink preparation process, and the ink's printability was thoroughly characterized to assure homogeneous and reproducible printing results. A new buffer mediated synthesis method for GG-MA resulted in consistent degrees of substitution which allowed the creation of large 5 g batches. We found that both the new synthesis as well as cryomilling of the polymer components of the ink resulted in a decrease in viscosity from 113 kPa·s to 11.3 kPa·s at a shear rate of 0.1 s−1 but increased ink homogeneity. The ink homogeneity was assessed through thermogravimetric analysis and a newly developed extrusion force measurement setup. The ink displayed strong inter-layer adhesion between two printed ink layers as well as between a layer of ink with and a layer without HAp. The large polymer batch production along with the characterization of the ink during the manufacturing process allows ink production in the gram scale and could be used in applications such as the printing of osteochondral grafts.
AUTHOR Tan, Wen See and Juhari, Muhammad Aidil Bin and Shi, Qian and Chen, Shengyang and Campolo, Domenico and Song, Juha
Title Development of a new additive manufacturing platform for direct freeform 3D printing of intrinsically curved flexible membranes [Abstract]
Year 2020
Journal/Proceedings Additive Manufacturing
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Abstract
The wearable technology market has been expanding from wearable medical devices for non-invasive continuous monitoring of patient vital signs to wearable devices for tracking fitness activities that any person can access. Regardless of their form or function, desirable characteristics of wearable devices are the ability to be flexible, conformal, and easily attachable to the human body. However, as the human body is intrinsically curved and irregular, flat devices often have poor interfacial adhesion with the human body. This often leads to interfacial delamination and eventual detachment of the device. Therefore, a new additive manufacturing (AM) platform, a direct freeform 3D printing process (DF3DP), is proposed to allow direct construction of intrinsically curved 3D surfaces during the material deposition phase without the need for any pre-shaped supporting molds or templates. This 3D freeform printing process involves a supporting matrix made up of calcium alginate microgels, printing material made from silicone ink, and freeform printing paths derived from customized G-codes that conform exactly to the scanned human surface profile. Curved meshes mimicking the human elbow were used as a demonstration. A static contact stability test showed that the printed 3D silicone mesh was highly conformal to the model elbow surface as compared to a 2D flat mesh. A dynamic contact stability test was also conducted by subjecting both meshes to 100 cycles of mechanical flexion and extension, proving that intrinsically curved surfaces can provide better contact stability for complex human body surfaces undergoing motion than can flat surfaces. These results have proven that intrinsically curved membranes or structures fabricated by DF3DP can reduce the interfacial shear stress and occurrence of cracks and delamination while maintaining structural integrity and stability during use without compromising the comfort of the users. Our approach can resolve interfacial issues in flexible substrates and has great potential for epidermal devices or soft robotics via its long-term sustainable performance.
AUTHOR Zhang, Hua and Cong, Yang and Osi, Amarachi Rosemary and Zhou, Yang and Huang, Fangcheng and Zaccaria, Remo P. and Chen, Jing and Wang, Rong and Fu, Jun
Title Direct 3D Printed Biomimetic Scaffolds Based on Hydrogel Microparticles for Cell Spheroid Growth [Abstract]
Year 2020
Journal/Proceedings Advanced Functional Materials
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Abstract
Abstract Biocompatible hydrogel inks with shear-thinning, appropriate yield strength, and fast self-healing are desired for 3D bioprinting. However, the lack of ideal 3D bioprinting inks with outstanding printability and high structural fidelity, as well as cell-compatibility, has hindered the progress of extrusion-based 3D bioprinting for tissue engineering. In this study, novel self-healable pre-cross-linked hydrogel microparticles (pcHμPs) of chitosan methacrylate (CHMA) and polyvinyl alcohol (PVA) hybrid hydrogels are developed and used as bioinks for extrusion-based 3D printing of scaffolds with high fidelity and biocompatibility. The pcHμPs display excellent shear thinning when injected through a syringe and subsequently self-heal into gels as shear forces are removed. Numerical simulations indicate that the pcHμPs experience a plug flow in the nozzle with minimal disturbance, which favors a steady and continuous printing. Moreover, the pcHμPs show a self-supportive yield strength (540 Pa), which is critical for the fidelity of printed constructs. A series of biomimetic constructs with very high aspect ratio and delicate fine structures are directly printed by using the pcHμP ink. The 3D printed scaffolds support the growth of bone-marrow-derived mesenchymal stem cells and formation of cell spheroids, which are most important for tissue engineering.
AUTHOR Lee, Jia Min and Yeong, Wai Yee
Title Engineering macroscale cell alignment through coordinated toolpath design using support-assisted 3D bioprinting [Abstract]
Year 2020
Journal/Proceedings Journal of The Royal Society Interface
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Abstract
Aligned cells provide direction-dependent mechanical properties that influence biological and mechanical function in native tissues. Alignment techniques such as casting and uniaxial stretching cannot fully replicate the complex fibre orientation of native tissue such as the heart. In this study, bioprinting is used to direct the orientation of cell alignment. A 0°–90° grid structure was printed to assess the robustness of the support-assisted bioprinting technique. The variation in the angles of the grid pattern is designed to mimic the differences in fibril orientation of native tissues, where angles of cell alignment vary across the different layers. Through bioprinting of a cell–hydrogel mixture, C2C12 cells displayed directed alignment along the longitudinal axis of printed struts. Cell alignment is induced through firstly establishing structurally stable constructs (i.e. distinct 0°–90° structures) and secondly, allowing cells to dynamically remodel the bioprinted construct. Herein reports a method of inducing a macroscale level of controlled cell alignment with angle variation. This was not achievable both in terms of methods (i.e. conventional alignment techniques such as stretching and electrical stimulation) and magnitude (i.e. hydrogel features with less than 100 µm features).
AUTHOR Somasekharan, Lakshmi and Kasoju, Naresh and Raju, Riya and Bhatt, Anugya
Title Formulation and Characterization of Alginate Dialdehyde, Gelatin, and Platelet-Rich Plasma-Based Bioink for Bioprinting Applications [Abstract]
Year 2020
Journal/Proceedings Bioengineering
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Abstract
Layer-by-layer additive manufacturing process has evolved into three-dimensional (3D) “bio-printing” as a means of constructing cell-laden functional tissue equivalents. The process typically involves the mixing of cells of interest with an appropriate hydrogel, termed as “bioink”, followed by printing and tissue maturation. An ideal bioink should have adequate mechanical, rheological, and biological features of the target tissues. However, native extracellular matrix (ECM) is made of an intricate milieu of soluble and non-soluble extracellular factors, and mimicking such a composition is challenging. To this end, here we report the formulation of a multi-component bioink composed of gelatin and alginate -based scaffolding material, as well as a platelet-rich plasma (PRP) suspension, which mimics the insoluble and soluble factors of native ECM respectively. Briefly, sodium alginate was subjected to controlled oxidation to yield alginate dialdehyde (ADA), and was mixed with gelatin and PRP in various volume ratios in the presence of borax. The formulation was systematically characterized for its gelation time, swelling, and water uptake, as well as its morphological, chemical, and rheological properties; furthermore, blood- and cytocompatibility were assessed as per ISO 10993 (International Organization for Standardization). Printability, shape fidelity, and cell-laden printing was evaluated using the RegenHU 3D Discovery bioprinter. The results indicated the successful development of ADA–gelatin–PRP based bioink for 3D bioprinting and biofabrication applications.
AUTHOR Eltaher, Hoda M. and Abukunna, Fatima E. and Ruiz-Cantu, Laura and Stone, Zack and Yang, Jing and Dixon, James E.
Title Human-scale tissues with patterned vascular networks by additive manufacturing of sacrificial sugar-protein composites [Abstract]
Year 2020
Journal/Proceedings Acta Biomaterialia
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Combating necrosis, by supplying nutrients and removing waste, presents the major challenge for engineering large three-dimensional (3D) tissues. Previous elegant work used 3D printing with carbohydrate glass as a cytocompatible sacrificial template to create complex engineered tissues with vascular networks (Miller et al. 2012, Nature Materials). The fragile nature of this material compounded with the technical complexity needed to create high-resolution structures led us to create a flexible sugar-protein composite, termed Gelatin-sucrose matrix (GSM), to achieve a more robust and applicable material. Here we developed a low-range (25–37˚C) temperature sensitive formulation that can be moulded with micron-resolution features or cast during 3D printing to produce complex flexible filament networks forming sacrificial vessels. Using the temperature-sensitivity, we could control filament degeneration meaning GSM can be used with a variety of matrices and crosslinking strategies. Furthermore by incorporation of biocompatible crosslinkers into GSM directly, we could create thin endothelialized vessel walls and generate patterned tissues containing multiple matrices and cell-types. We also demonstrated that perfused vascular channels sustain metabolic function of a variety of cell-types including primary human cells. Importantly, we were able to construct vascularized human noses which otherwise would have been necrotic. Our material can now be exploited to create human-scale tissues for regenerative medicine applications. Statement of Significance Authentic and engineered tissues have demands for mass transport, exchanging nutrients and oxygen, and therefore require vascularization to retain viability and inhibit necrosis. Basic vascular networks must be included within engineered tissues intrinsically. Yet, this has been unachievable in physiologically-sized constructs with tissue-like cell densities until recently. Sacrificial moulding is an alternative in which networks of rigid lattices of filaments are created to prevent subsequent matrix ingress. Our study describes a biocompatible sacrificial sugar-protein formulation; GSM, made from mixtures of inexpensive and readily available bio-grade materials. GSM can be cast/moulded or bioprinted as sacrificial filaments that can rapidly dissolve in an aqueous environment temperature-sensitively. GSM material can be used to engineer viable and vascularized human-scale tissues for regenerative medicine applications.
AUTHOR Strauß, Svenja and Meutelet, Rafaela and Radosevic, Luka and Gretzinger, Sarah and Hubbuch, Jürgen
Title Image analysis as PAT-Tool for use in extrusion-based bioprinting [Abstract]
Year 2020
Journal/Proceedings Bioprinting
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The technology of bioprinting is arousing a growing interest in biopharmaceutical research and industry. In order to accelerate process development in the field of bioprinting, image-based analysis methods are non-invasive, time- and cost-saving tools which are usable for printer characterization, bioink printability evaluation, and process optimization. Image processing can also be used for the study of reproducibility, since reliable production is important in the transition from research to industrial application, and more precisely to clinical studies. This study revolves around the establishment of an automated and image-based line analysis method for bioprinting applications which enables an easy comparison of 3D-printed lines. Diverse rheological properties of bioinks and the printing process affect the geometry of the resulting object. The line represents a simple geometry, where the influence of the rheological properties and printing parameters is directly apparent. Therefore, a method for line analysis was developed on the basis of image recognition. At first, the method is tested for several substances such as Nivea®, pure and colored Kolliphor solutions, and two commercially available hydrogel formulations which can be used as bioinks. These are Biogelx™-ink-RGD by Biogelx and Cellink® Bioink by Cellink. The examination of limitations showed that transparent materials such as Kolliphor-based solutions cannot be analyzed with the developed method whereas opaque materials such as Nivea® and both bioinks can be analyzed. In the course of process characterization, the method was used to investigate the shrinkage behavior for both bionks. With the help of the line analysis tool, a shrinkage behavior of both bioinks was demonstrated and thus, process time could be identified as a critical process parameter.
AUTHOR Fisch, Philipp and Holub, Martin and Zenobi-Wong, Marcy
Title Improved accuracy and precision of bioprinting through progressive cavity pump-controlled extrusion [Abstract]
Year 2020
Journal/Proceedings bioRxiv
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Abstract
3D bioprinting has seen a tremendous growth in recent years in a variety of fields such as tissue and organ models, drug testing and regenerative medicine. This growth has led researchers and manufacturers to continuously advance and develop novel bioprinting techniques and materials. Although new bioprinting methods are emerging (e.g. contactless and volumetric bioprinting), micro-extrusion bioprinting remains the most widely used method. Micro-extrusion bioprinting, however, is still largely dependent on the conventional pneumatic extrusion process, which relies heavily on homogenous biomaterial inks and bioinks to maintain a constant material flowrate. Augmenting the functionality of the bioink with the addition of nanoparticles, cells or biopolymers can induce inhomogeneities resulting in uneven material flow during printing and/or clogging of the nozzle, leading to defects in the printed construct. In this work, we evaluated a novel extrusion technique based on a miniaturized progressive cavity pump. We compared the accuracy and precision of this system to the pneumatic extrusion system and tested both for their effect on cell viability after extrusion. The progressive cavity pump achieved a significantly higher accuracy and precision compared to the pneumatic system while maintaining good viability and was able to maintain its reliability independently of the bioink composition, printing speed or nozzle size. Progressive cavity pumps are a promising tool for bioprinting and could help provide standardized and validated bioprinted constructs while leaving the researcher more freedom in the design of the bioinks with increased functionality.
AUTHOR Rupp, Harald and Binder, Wolfgang H.
Title Multicomponent Stress-Sensing Composites Fabricated by 3D-Printing Methodologies [Abstract]
Year 2020
Journal/Proceedings Macromolecular Rapid Communications
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Abstract The preparation and characterization of mechanoresponsive, 3D-printed composites are reported using a dual-printing setup for both, liquid dispensing and fused-deposition-modeling. The here reported stress-sensing materials are based on high- and low molecular weight mechanophores, including poly(ε-caprolactone)-, polyurethane-, and alkyl(C11)-based latent copper(I)bis(N-heterocyclic carbenes), which can be activated by compression to trigger a fluorogenic, copper(I)-catalyzed azide/alkyne “click”-reaction of an azide-functionalized fluorescent dye inside a bulk polymeric material. Focus is placed on the printability and postprinting activity of the latent mechanophores and the fluorogenic “click”-components. The multicomponent specimen containing both, azide and alkyne, are manufactured via a 3D-printer to place the components separately inside the specimen into void spaces generated during the FDM-process, which subsequently are filled with liquids using a separate liquid dispenser, located within the same 3D-printing system. The low-molecular weight mechanophores bearing the alkyl-C11 chains display the best printability, yielding a mechanochemical response after the 3D-printing process.
AUTHOR Lee, Mihyun and Bae, Kraun and Levinson, Clara and Zenobi-Wong, Marcy
Title Nanocomposite bioink exploits dynamic covalent bonds between nanoparticles and polysaccharides for precision bioprinting [Abstract]
Year 2020
Journal/Proceedings Biofabrication
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Abstract
The field of bioprinting has made significant recent progress towards engineering tissues with increasing complexity and functionality. It remains challenging, however, to develop bioinks with optimal biocompatibility and good printing fidelity. Here, we demonstrate enhanced printability of a polymer-based bioink based on dynamic covalent linkages between nanoparticles (NPs) and polymers, which retains good biocompatibility. Amine-presenting silica NPs (ca. 45 nm) were added to a polymeric ink containing oxidized alginate (OxA). The formation of reversible imine bonds between amines on the NPs and aldehydes of OxA lead to significantly improved rheological properties and high printing fidelity. In particular, the yield stress increased with increasing amounts of NPs (14.5 Pa without NPs, 79 Pa with 2 wt% NPs). In addition, the presence of dynamic covalent linkages in the gel provided improved mechanical stability over 7 d compared to ionically crosslinked gels. The nanocomposite ink retained high printability and mechanical strength, resulting in generation of centimeter-scale porous constructs and an ear structure with overhangs and high structural fidelity. Furthermore, the nanocomposite ink supported both in vitro and in vivo maturation of bioprinted gels containing chondrocytes. This approach based on simple oxidation can be applied to any polysaccharide, thus the widely applicability of the method is expected to advance the field towards the goal of precision bioprinting.
AUTHOR Cernecu, Alexandra and Lungu, Adriana and Stancu, Izabela Cristina and Vasile, Eugeniu and Iovu, Horia
Title Polysaccharide-Based 3D Printing Inks Supplemented with Additives
Year 2020
Journal/Proceedings University Politechnica of Bucharest Scientific Bulletin
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AUTHOR Tan, Wen See and Shi, Qian and Chen, Shengyang and Bin Juhari, Muhammad Aidil and Song, Juha
Title Recyclable and biocompatible microgel-based supporting system for positive 3D freeform printing of silicone rubber [Abstract]
Year 2020
Journal/Proceedings Biomedical Engineering Letters
Reftype Tan2020
DOI/URL DOI
Abstract
Additive manufacturing (AM) of biomaterials has evolved from a rapid prototyping tool into a viable approach for the manufacturing of patient-specific implants over the past decade. It can tailor to the unique physiological and anatomical criteria of the patient’s organs or bones through precise controlling of the structure during the 3D printing. Silicone elastomers, which is a major group of materials in many biomedical implants, have low viscosities and can be printed with a special AM platform, known as freeform 3D printing systems. The freeform 3D printing systems are composed of a supporting bath and a printing material. Current supporting matrices that are either commercially purchased or synthesized were usually disposed of after retrieval of the printed part. In this work, we proposed a new and improved supporting matrix comprises of synthesized calcium alginate microgels produced via encapsulation which can be recycled, reused, and recovered for multiple prints, hence minimizing wastage and cost of materials. The dehydration tolerance of the calcium alginate microgels was improved through physical means by the addition of glycerol and chemical means by developing new calcium alginate microgels encapsulated with glycerol. The recyclability of the heated calcium alginate microgels was also enhanced by a rehydration step with sodium chloride solution and a recovery step with calcium chloride solution via the ion exchange process. We envisaged that our reusable and recyclable biocompatible calcium alginate microgels can save material costs, time, and can be applied in various freeform 3D printing systems.
AUTHOR Sanz-Fraile, Hector and Amorós, Susana and Mendizabal, Irene Isabel and Gálvez-Montón, Carolina and Prat-Vidal, Cristina and Bayés-Genís, Antoni and Navajas, Daniel and Farre, Ramon and Otero, Jorge
Title Silk-reinforced Collagen Hydrogels with Raised Multiscale Stiffness for Mesenchymal Cells 3D Culture [Abstract]
Year 2020
Journal/Proceedings Tissue Engineering Part A
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Type I collagen hydrogels are of high interest in tissue engineering. With the evolution of 3D bioprinting technologies, a high number of collagen-based scaffolds have been reported for the development of 3D cell cultures. A recent proposal was to mix collagen with silk fibroin derived from Bombyx Mori silkworm. Nevertheless, due to the difficulties in the preparation and the characteristics of the protein, several problems like phase separation and collagen denaturation appears during the procedure. Therefore, the common solution is to diminish the concentration of collagen although in that way the most biologically relevant component is reduced. In the present work, we present a new, simple and effective method to develop a collagen-silk hybrid hydrogel with high collagen concentration and with increased stiffness approaching that of natural tissues, which could be of high interest for the development of cardiac patches for myocardial regeneration and for preconditioning of mesenchymal stem cells to improve their therapeutic potential. Sericin in the silk was preserved by using a physical solubilizing procedure which results in a preserved fibrous structure of type I collagen, as shown by ultrastructural imaging. The macro- and micromechanical properties of the hybrid hydrogels measured by tensile stretch and Atomic Force Microscopy respectively, showed a more than two-fold stiffening as compared with collagen-only hydrogels. Rheological measurements showed improved printability properties for the developed biomaterial. The suitability of the hydrogels for 3D cell culture was assessed by 3D bioprinting bone marrow-derived mesenchymal stem cells cultured within the scaffolds. The result was a biomaterial with improved printability characteristics that better resembled the mechanical properties of natural soft tissues while preserving biocompatibility owing to the high concentration of collagen.
AUTHOR Li, Huijun and Tan, Yu Jun and Kiran, Raj and Tor, Shu Beng and Zhou, Kun
Title Submerged and non-submerged 3D bioprinting approaches for the fabrication of complex structures with the hydrogel pair GelMA and alginate/methylcellulose [Abstract]
Year 2020
Journal/Proceedings Additive Manufacturing
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Abstract
The extrusion-based bioprinting of hydrogels such as gelatin methacrylate (GelMA) into structures with complex shape suffers from poor printability due to their low viscosity. The present study deals with hydrogel materials by using the mixture of cell-laden photopolymerizable GelMA as a main printing material and the mixture of alginate and methylcellulose (Alg/MC) as a support material because of its high viscosity and good thixotropic property. One extrusion-based approach is developed by printing the two mixtures into structures in an alternating layer-by-layer manner, with the electrostatic interactions between polycationic GelMA and polyanionic Alg/MC contributing to the integrity of the structures. The final printed structures are exposed to ultraviolet (UV) light to form crosslinks in GelMA through photopolymerization for further structural strengthening. The one-time UV exposure minimizes cell damage in cell-GelMA, demonstrating an advantage over those in previously reported studies that required repeated UV exposures upon the printing of each layer of a structure. The other approach is developed by submerging the extrusion nozzle into a bath of Alg/MC to print cell-laden GelMA structures, which, upon printing completion, are also subject to one-time UV exposure before the removal of the support material Alg/MC. A flower with living cells is printed to demonstrate the capability of the second approach of fabricating structures with geometric complexity. The structures printed using both approaches demonstrate a well-maintained shape fidelity, structural integrity and cell viability of over 93% up to five culturing days. The proposed two printing approaches based on the cell-GelMA and Alg/MC pair will be beneficial for exploring new opportunities in bioprinting.
AUTHOR Schwab, Andrea and Helary, Christophe and Richards, Geoff and Alini, Mauro and Eglin, David and D{textquoteright}Este, Matteo
Title Tissue mimetic hyaluronan bio-ink containing oriented collagen fibers to modulate hMSC spreading and differentiation [Abstract]
Year 2020
Journal/Proceedings bioRxiv
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DOI/URL URL DOI
Abstract
Biofabrication is providing scientists and clinicians the ability to produce engineered tissues with desired shapes, chemical and biological gradients. Typical resolutions achieved with extrusion-based bioprinting are at the macroscopic level. However, for capturing the fibrillar nature of the extracellular matrix (ECM), it is necessary to arrange ECM components at smaller scales, down to the sub-micron and the molecular level.In this study, we introduce a (bio)ink containing hyaluronan (HA) as tyramine derivative (THA) and collagen (Col). Similarly to other connective tissues, in this (bio)ink Col is present in fibrillar form and HA as viscoelastic space filler. THA was enzymatically crosslinked under mild conditions allowing simultaneous Col fibrillogenesis, thus achieving a homogeneous distribution of Col fibrils within the viscoelastic HA-based matrix. THA-Col composite displayed synergistic properties in terms of storage modulus and shear-thinning, translating into good printability.Shear-induced alignment of the Col fibrils along the printing direction was achieved and quantified via immunofluorescence and second harmonic generation.Cell-free and cell-laden constructs were printed and characterized, analyzing the influence of the controlled microscopic anisotropy on cell behavior and chondrogenic differentiation.THA-Col showed cell instructive properties modulating hMSC adhesion, morphology and sprouting from spheroids stimulated by the presence and the orientation of Col fibers. Actin filament staining showed that hMSCs embedded into aligned constructs displayed increased cytoskeleton alignment along the fibril direction. Based on gene expression of cartilage/bone markers and matrix production, hMSCs embedded into the bioink displayed chondrogenic differentiation comparable or superior to standard pellet culture by means of proteoglycan production (Safranin O staining and proteoglycan quantification) as well as increase in cartilage related genes.The possibility of printing matrix components with control over microscopic alignment brings biofabrication one step closer to capturing the complexity of native tissues.
AUTHOR Shapira, Assaf and Noor, Nadav and Oved, Hadas and Dvir, Tal
Title Transparent support media for high resolution 3D printing of volumetric cell-containing ECM structures [Abstract]
Year 2020
Journal/Proceedings Biomedical Materials
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DOI/URL DOI
Abstract
3D bioprinting may revolutionize the field of tissue engineering by allowing fabrication of bio-structures with high degree of complexity, fine architecture and heterogeneous composition. The printing substances in these processes are mostly based on biomaterials and living cells. As such, they generally possess weak mechanical properties and thus must be supported during fabrication in order to prevent the collapse of large, volumetric multi-layered printouts. In this work, we characterize a uniquely formulated media used to support printing of extracellular matrix-based biomaterials. We show that a hybrid material, comprised of calcium-alginate nanoparticles and xanthan gum, presents superb qualities that enable printing at high resolution of down to 10 microns, allowing fabrication of complex constructs and cellular structures. This hybrid also presents an exclusive combination of desirable properties such as biocompatibility, high transparency, stability at a wide range of temperatures and amenability to delicate extraction procedures. Moreover, as fabrication of large, volumetric biological structures may require hours and even days to accomplish, we have demonstrated that the hybrid medium can support prolonged, precise printing for at least 18 hours. All these qualities make it a promising support medium for 3D printing of tissues and organs.
AUTHOR Döhler, Diana and Kang, Jiheong and Cooper, Chris Brittain and Tok, Jeffrey B.-H. and Rupp, Harald and Binder, Wolfgang H. and Bao, Zhenan
Title Tuning the Self-Healing Response of Poly(dimethylsiloxane)-Based Elastomers [Abstract]
Year 2020
Journal/Proceedings ACS Appl. Polym. Mater.
Reftype
DOI/URL DOI
Abstract
We present a comprehensive investigation of mechanical properties of supramolecular polymer networks with rationally developed multistrength hydrogen-bonding interactions. Self-healing poly(dimethylsiloxane) (PDMS)-based elastomers with varying elasticity, fracture toughness, and the ability to dissipate strain energy through the reversible breakage and re-formation of the supramolecular interactions were obtained. By changing the ratio between isophorone diisocyanate (IU), 4,4′-methylenebis(cyclohexyl isocyanate) (MCU), and 4,4′-methylenebis(phenyl isocyanate) (MPU) and by varying the molecular weight of the PDMS precursor, we obtained a library of poly(urea)s to study the interplay of mechanical performance and self-healability. The Young’s moduli of the presented materials ranged between 0.4 and 13 MPa and increased with decreasing molecular weight of the PDMS precursor and increasing content of MCU or MPU units related to the formation of stronger hydrogen-bonding interactions. By exchanging MPU against MCU units, we achieved an optimum balance between mechanical properties and self-healing performance, and by the additional reduction of the molecular weight of the precursor polymer, a minimum recovery of 80% in stress within 12 h at room temperature was observed. Selected poly(urea)s could be processed via 3D printing by the conventional extrusion method, obtaining dimensionally stable and freestanding objects. We present a comprehensive investigation of mechanical properties of supramolecular polymer networks with rationally developed multistrength hydrogen-bonding interactions. Self-healing poly(dimethylsiloxane) (PDMS)-based elastomers with varying elasticity, fracture toughness, and the ability to dissipate strain energy through the reversible breakage and re-formation of the supramolecular interactions were obtained. By changing the ratio between isophorone diisocyanate (IU), 4,4′-methylenebis(cyclohexyl isocyanate) (MCU), and 4,4′-methylenebis(phenyl isocyanate) (MPU) and by varying the molecular weight of the PDMS precursor, we obtained a library of poly(urea)s to study the interplay of mechanical performance and self-healability. The Young’s moduli of the presented materials ranged between 0.4 and 13 MPa and increased with decreasing molecular weight of the PDMS precursor and increasing content of MCU or MPU units related to the formation of stronger hydrogen-bonding interactions. By exchanging MPU against MCU units, we achieved an optimum balance between mechanical properties and self-healing performance, and by the additional reduction of the molecular weight of the precursor polymer, a minimum recovery of 80% in stress within 12 h at room temperature was observed. Selected poly(urea)s could be processed via 3D printing by the conventional extrusion method, obtaining dimensionally stable and freestanding objects.
AUTHOR Alison, Lauriane and Menasce, Stefano and Bouville, Florian and Tervoort, Elena and Mattich, Iacopo and Ofner, Alessandro and Studart, André R.
Title 3D printing of sacrificial templates into hierarchical porous materials [Abstract]
Year 2019
Journal/Proceedings Scientific Reports
Reftype Alison2019
DOI/URL DOI
Abstract
Hierarchical porous materials are widespread in nature and find an increasing number of applications as catalytic supports, biological scaffolds and lightweight structures. Recent advances in additive manufacturing and 3D printing technologies have enabled the digital fabrication of porous materials in the form of lattices, cellular structures and foams across multiple length scales. However, current approaches do not allow for the fast manufacturing of bulk porous materials featuring pore sizes that span broadly from macroscopic dimensions down to the nanoscale. Here, ink formulations are designed and investigated to enable 3D printing of hierarchical materials displaying porosity at the nano-, micro- and macroscales. Pores are generated upon removal of nanodroplets and microscale templates present in the initial ink. Using particles to stabilize the droplet templates is key to obtain Pickering nanoemulsions that can be 3D printed through direct ink writing. The combination of such self-assembled templates with the spatial control offered by the printing process allows for the digital manufacturing of hierarchical materials exhibiting thus far inaccessible multiscale porosity and complex geometries.
AUTHOR Rupp, Harald and Döhler, Diana and Hilgeroth, Philipp and Mahmood, Nasir and Beiner, Mario and Binder, Wolfgang H.
Title 3D Printing of Supramolecular Polymers: Impact of Nanoparticles and Phase Separation on Printability [Abstract]
Year 2019
Journal/Proceedings Macromolecular Rapid Communications
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DOI/URL DOI