Covalent and environment-responsive biopolymer hydrogel for drug delivery and wound healing

Biopolymer-based hydrogels are important cell scaffolding materials for drug delivery and regenerative medicine. In this study, we report a covalently cross-linked composite chitosan-alginate hydrogel possessing pH sensitivity to degradation for drug delivery. To enhance mechanical strength of hydrogel, polyvinyl alcohol (PVA) was also added to form hydrogen bonds with polysaccharides under physiological condition. The gelation mechanism is attributed to the Schiff-base reaction occurring between amino groups in carboxymethyl chitosan (CMCS) and aldehyde groups in oxidized sodium alginate (OAlg). Synchronously, to enhance antibacterial properties of biomaterials, 5-fluorouracil (5-Flu) was mechanically mixed in the PVA solution, followed by incorporation into the CMCS-OAlg hydrogel to form a composite gel scaffold. Molecular weight and concentration of PVA would affect the gelation morphology, mechanical properties, swelling ratio, in vitro degradation and pH sensitivity of the gel scaffold. The composite gel scaffold has good drug release and antibacterial properties through drug release calculation and antibacterial performance evaluation. These results indicate that the composite gel scaffold has great potential for pH-sensitive drug delivery and wound healing applications.