Optimization of thermoresponsive chitosan/B-glycerophosphate hydrogels for injectable neural tissue engineering application

Regeneration of neural tissue and recovery of lost functions following an accident or disease to the central nervous system remains a major challenge worldwide, with limited treatment options available. The main reason for the failure of conventional therapeutic techniques to regenerate neural tissue is the presence of blood-brain barrier separating nervous system from systemic circulation and the limited capacity of self-regeneration of the nervous system. Injectable hydrogels have shown great promise for neural tissue engineering given their suit-ability for minimally invasive in situ delivery and tunable mechanical and biological properties. Chitosan (CS)/ B-glycerophosphate (B-GP) hydrogels have been extensively investigated and shown regenerative potential in a wide variety of tissues such as bone and cartilage tissue engineering. However, the potential of CS/B-GP hydrogels has never been tested for injectable neural tissue engineering applications. In the present study, CS/ B-GP hydrogels, consisting of 0.5-2% CS and 2-3% B-GP, were prepared and characterized to investigate their suitability for injectable neural tissue engineering applications. The resulting CS/B-GP-hydrogels showed a varying range of properties depending on the CS/B-GP blend ratio. In particular, the 0.5%:3% and 0.75%:3% CS/ B-GP hydrogels underwent rapid gelation (3 min and 5 min, respectively) at physiological temperature (37 degrees C) and pH (7.4). They also had suitable porosity, osmolality, swelling behavior and biodegradation for tissue en-gineering. The biocompatibility of hydrogels was determined in vitro using PC12 cells, an immortalized cell line with neuronal cell-like properties, revealing that these hydrogels supported cell growth and proliferation. In conclusion, the thermoresponsive 0.5%:3% and 0.75%:3% CS/B-GP hydrogels had the greatest potential for neural tissue engineering.