In situ formation of silver nanoparticles-contained gelatin-PEG-dopamine hydrogels via enzymatic cross-linking reaction for improved antibacterial activities.

Hydrogels containing silver nanoparticles (AgNPs) were recently found to exhibit excellent antibacterial properties against both gram-negative/positive bacteria and fungi. In this study, we reported the synthesis of AgNPs-contained gelatin-polyethylene glycol-dopamine (AgNP-GPD) hydrogels via the in situ formation of AgNPs in GPD polypeptide solution, followed by an enzymatic cross-linking reaction to form hydrogels. The experimental results showed that the reducing reaction exerted by GPD polypeptides under physiological conditions can afford the formation of AgNPs in situ in the polypeptide solution without the need for additional reducing agents and/or processes such as UV or thermal treatments and then the hydrogelation of GPD polypeptide solution containing AgNPs were preceeded via enzymatic cross-linking reaction. It was found that the gelation time, hydrogel mechanical property, degree of swelling and degree of enzymatic degradation for both GPD and AgNP-GPD hydrogels can be tuned by varying enzyme/oxidative agent concentration, catechol content, and reducing reaction conditions such as reaction time and silver ion concentration. Importantly, AgNP-GPD hydrogels exhibit excellent antibacterial properties against gram-negative and gram-positive bacteria. This type of hydrogel is a promising biomaterial for biomedical applications including wound healing and tissue engineering.