In situ gelling polysaccharide-based hydrogel for cell and drug delivery in tissue engineering

Injectable hydrogels have attracted a great deal of attention as cell carriers and bioactive agents in regenerative medicine due to their ability to fill complex three-dimensional (3D) tissue gaps and relative ease of in vivo administration. Polysaccharide-based hydrogels can provide microenvironments that favor tissue regeneration and biocompatibility due to their chemical similarities with native extracellular matrix components. This manuscript reports the in vitro application of an injectable chitosan-based polysaccharide hydrogel for cell and protein delivery. Crosslinked hydrogels were produced by the reaction between the amino functionality of chitosan and the aldehyde of dextran aldehyde resulting in an imine bond (Schiff's base) formation in aqueous solutions. This approach eliminated the use of additional crosslinking agents which may pose undesired side effects regarding cytotoxicity and biocompatibility. Additionally, we demonstrate versatility of the gel in terms of its fabrication, and ability to alter mechanical properties by changing the crosslinking extent due to aldehyde content. Bovine serum albumin (BSA), used as a model protein, followed a steady release pattern from the gel. BSA release was dependent on the extent of hydrogel crosslinking. Increase in crosslinking extent resulted in improved mechanical properties and sustained release of BSA. Human fetal osteoblasts encapsulated into the hydrogel showed at least 70% viability and continued to proliferate under in vitro culture.