Dually Responsive Injectable Hydrogel Prepared by In Situ Cross-Linking of Glycol Chitosan and Benzaldehyde-Capped PEO-PPO-PEO

Injectable hydrogels with pH and temperature triggered drug release capability were synthesized based on biocompatible glycol chitosan and benzaldehyde-capped poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) (PEO-PPO-PEO). Aqueous solutions of the above polymers formed hydrogel under physiological conditions, allowing a desirable injectability, through the formation covalent benzoic-imine bond with pH and temperature changes. Rheological characterization demonstrated that the gelation rate and the moduli of the hydrogels were able to be tuned with chemical composition as well as pH and temperature of the polymer solution. Both hydrophobic and hydrophilic drugs could be incorporated inside the hydrogel through the in situ gel forming process and undergo a controlled release by altering pH or temperature. In vivo tests proved the formation and biocompatibility of the hydrogel in rat model.