Cold-adaptation of a methacrylamide gelatin towards the expansion of the biomaterial toolbox for specialized functionalities in tissue engineering.

Tissue regeneration is witnessing a significant surge in advanced medicine. It requires the interaction of scaffolds with different cell types for efficient tissue formation post-implantation. The presence of tissue subtypes in more complex organs demands the co-existence of different biomaterials showing different hydrolysis rate for specialized cell-dependent remodeling. To expand the available toolbox of biomaterials with sufficient mechanical strength and variable rate of enzymatic degradation, a cold-adapted methacrylamide gelatin was developed from salmon skin. Compared with mammalian methacrylamide gelatin (GelMA), hydrogels derived from salmon GelMA displayed similar mechanical properties than the former. Nevertheless, salmon gelatin and salmon GelMA-derived hydrogels presented characteristics common of cold-adaptation, such as reduced activation energy for collagenase, increased enzymatic hydrolysis turnover of hydrogels, increased interconnected polypeptides molecular mobility and lower physical gelation capability. These properties resulted in increased cell-remodeling rate in vitro and in vivo, proving the potential and biological tolerance of this mechanically adequate cold-adapted biomaterial as alternative scaffold subtypes with improved cell invasion and tissue fusion capacity.

Layer-by-layer approach for a uniformed fabrication of a cell patterned vessel-like construct.

Successful tissue engineered small diameter blood vessels (SDBV) require manufacturing systems capable of precisely controlling different key elements, such as material composition, geometry and spatial location of specialized biomaterials and cells types. We report in this work an automated methodology that enables the manufacture of multilayer cylindrical constructs for SDBV fabrication that uses a layer-by-layer deposition approach while controlling variables such as dipping and spinning speed of a rod and biomaterial viscosity. Different biomaterials including methacrylated gelatin, alginate and chitosan were tested using this procedure to build different parts of the constructs. The system was capable of controlling dimensions of lumen from 0.5 mm up to 6 mm diameter and individual layers from 1 µm up to 400 µm thick. A cellular component was successfully added to the biomaterial in the absence of significant cytotoxic effect which was assessed by viability and proliferation assays. Additionally, cells showed a homogenous distribution with well-defined concentric patterns across the multilayer vessel grafts. The challenging generation of inner endothelial cells of approximately 20-30 µm of thickness was achieved. Preliminary experimental evidences of microstructural alignment of the biomaterial were obtained when the dipping approach was combined with the rod rotation. The study demonstrated the wide versatility and scalability of the automated system to easily and rapidly fabricate complex cellularized multilayer vascular grafts with structural configuration that resembles natural blood vessels.