Imidazolyl crosslinked chitosan nanogel for nanoconfined synthesis of silver nanocrystallines as antimicrobials

Multi-drug resistant microbes (MDRMs) present a significant threat to human health. Silver nanoparticles possess broad-spectrum antimicrobial properties, but the potential Ag⁺ ion release and toxicity on primary cells drawback the clinical application. In this study, imidazolylhydrazine was employed to cross-link chitosan into nanogels and subsequently to synthesize nanoconfined silver nanocrystallines. These silver nanocrystallines are predominantly characterized by (111) crystalline facets, featuring a high Ag⁰ atomic density and an approximate size of 3 nm. these nanocrystallines demonstrated exceptional visible light bactericidal properties, particularly against MDRMs, attributable to a threefold enhancement in reactive oxygen species (ROS) generation efficiency compared to silver nanoparticles. Remarkably, thanks to the nanoconfined domains of the silver nanocrystallines embedded within the nanogel, along with the gel's strong coordination capabilities with Ag through its imidazole, hydrazide, and amino groups, as well as the proton buffering capacity of imidazole, the release of silver ions in the body fluid environment was not significantly observed at any stage of the wound recovery. This ensures exceptional biocompatibility for postoperative wound spraying. The nanoconfined Ag nanocrystalline platform emerges as a novel prospect for wound sterilization.