RESOURCES

Abstract
Abstract Gelatin-methacryloyl (GelMA) hydrogel has gained huge success in the last decades thanks to its versatilities in many applications. Notably, one of them is 3D bioprinting, as GelMA physical-mechanical properties and biocompatibility of uncured formulation perfectly suit the requirements of a bioink. Nevertheless, before the photopolymerization, the hydrogel shows weak mechanical properties and long recovery time after stress application, which results in the inability to obtain complex and self-standing forms due to structure collapse. In this work, Carbopol ETD 2020 NF, dissolved in cell culture medium, was used as supporting bath to optimize GelMA bioprinting and overcome its stability limitations. The achieved results demonstrated the possibility of printing shapes containing hollows with lumens or non-planar surfaces, also by using nozzles with larger inner diameter, which reduced cell death during printing process, but were usually avoid because of low resolution. Moreover, constructs' extraction was easier when Carbopol solution was prepared in culture medium rather than in water, reducing sample handling. In conclusion, thanks to this supporting bath, it was possible to print cellularized scaffold, with channels that were then seeded, obtaining inner structure. Further, this Carbopol formulation could be considered an eligible candidate as a supporting bath to obtain GelMA 3D self-standing-shaped and vascularized scaffold.

Abstract
The study proposes a platform for the formation and culture of non-small cell lung cancer (NSCLC) spheroids, to obtain an in vitro model suitable for drug and therapy testing. To achieve that, traditional cell culture is compared to methacrylated gelatin (GelMA) 3D bioprinting, in order to explore not only the potential of the matrix itself, but also the impact of different architectures on spheroid formation. Starting from a systematic analysis, where GelMA concentration, methacrylation degree and cell seeding concentration is set; three different architectures (round, ring and grid) are analyzed in terms of spheroid formation and growth, using 3D bioprinting. The study reveals that Very High GelMA 7.5% w/v formulation, with single cells dispersed in, is the best bioink to obtain NSCLC spheroids. Moreover, grid architecture performs in the best way, because of the highest volume-surface area ratio. The designed GelMA platform can be used as a powerful in vitro tool for drug testing and therapy screening, that can be designed playing with four different parameters: cell concentration, GelMA methacrylation degree, GelMA concentration and geometry.

Abstract
Three dimensional (3D) bioprinting technology has been making a progressive advancement in the field of tissue engineering to produce tissue constructs that mimic the shape, framework, and microenvironment of an organ. The technology has not only paved the way to organ development but has been widely studied for its application in drug and cosmetic testing using 3D bioprinted constructs. However, not much has been explored on the utilization of bioprinting technology for the development of tumor models to test anti-cancer drug efficacy. The conventional methodology involves a two dimensional (2D) monolayer model to test cellular drug response which has multiple limitations owing to its inability to mimic the natural tissue environment. The choice of bioink for 3D bioprinting is critical as cell morphology and proliferation depend greatly on the property of bioink. In this study, we developed a multicomponent bioink composed of alginate, diethylaminoethyl cellulose, gelatin, and collagen peptide to generate a 3D bioprinted construct. The bioink has been characterised and validated for its printability, shape fidelity and biocompatibility to be used for generating tumor models. Further, a bioprinted tumor model was developed using lung cancer cell line and the efficacy of 3D printed construct for drug screening application was established.