Ultrasmall gold Nanoparticles/Carboxymethyl chitosan composite hydrogel: Tough, restorable, biocompatible antimicrobial dressing for wound healing

Bacterial infection is one of the most challenging tasks in biomedical fields and still remains a serious threat to human lives today. Antibacterial hydrogel has attracted increasing scholarly interest as a promising wound dressing material. The antibacterial properties of ultrasmall gold nanoparticles (UsAuNPs) have also been widely recognized. Developing a tensile, self-healable, biocompatible composite hydrogel with desirable antibacterial properties to facilitate wound recovery is essential to improve treatment outcomes. However, UsAuNPs selfaggregate easily, resulting in decreased antibacterial effectiveness and limited clinical application. To address this problem, a composite material, UsAuNPs and carboxymethyl chitosan (UsAuNPs@CMCS) was designed. CMCS limit the self-aggregation of gold nanoparticles (AuNPs) at the size of 1-3 nm and attracts bacteria carrying negative charge on the surface, which renders the high antibacterial efficacy of the composite material. When the composite was crosslinked with the highly compatible polyacrylic acid (PAA) backbone of the hydrogel, the resulting PAA-CMCS-Au hydrogel displayed desirable antibacterial properties and facilitated wound recovery in vivo. This research establishes a new strategy to prevent the self-aggregation of UsAuNPs, and provides new insights in treating wounds with antibacterial composite hydrogels.