Researchers from Albert-Ludwigs-Universität Freiburg im Breisgau, Université Claude Bernard Lyon 1, Universidad Central “Marta Abreu”​ de Las Villas and Johannes Gutenberg-Universität Mainz developed a 3d printable, bioinspired hydrogel composed of two different biopolymers, chitosan and cellulose nanofibers, through an environmentally friendly process by avoiding both chemical modification of the components and additional chemical crosslinking in their processing. 
The bioinspired hydrogel composition and processing parameters were optimized to improve the quality of the constructs fabricated through micro-extrusion technology by means of REGENHU 3D Bioprinters.
By exploiting the dedicated design software and high-accuracy automated calibration mechanisms of the system, researchers were able to perform the process directly within Petri dishes filled with a neutralization solution for chitosan, acting as a coagulation bath to enable high-fidelity scaffold fabrication. 
Through this optimization process, they obtained constructs presenting high fidelity, good mechanical performance, anisotropic microstructure and suitable biological response. The authors envision this functional hydrogel to be exploited as a biomimetic alternative in tissue engineering of mechanically demanding tissues such as intervertebral disc.

Discover more here : https://www.mdpi.com/2073-4360/13/10/1663


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.