# In Situ Formation of Silver Nanoparticles-Containing Gallic Acid-Conjugated Chitosan Hydrogels as Antimicrobial Tissue Adhesive Materials

## TL;DR

This paper introduces a new type of antimicrobial hydrogel that forms in situ and sticks well to tissues, showing promise for wound healing and biomedical applications.

## Contribution

The novel contribution is the development of in situ formed Ag NP-containing CHI-G hydrogels with strong adhesion, antimicrobial properties, and biocompatibility.

## Key findings

- Ag/CHI-G hydrogels were formed without additional reducing agents or crosslinkers.
- The hydrogels showed excellent adhesion to porcine intestinal tissue and inhibited E. coli and S. aureus.
- They exhibited no significant cytotoxicity against fibroblast cell lines.

## Abstract

Antimicrobial hydrogels have attracted considerable attention for wound treatment due to the major clinical challenges of bacterial infections, which lead to delayed tissue regeneration and chronic inflammation. In addition, the strong adhesion of antimicrobial hydrogels to tissue surfaces is essential because wounds are generally moist, topographically irregular, and continuously exposed to various biological molecules. In this study, we developed in situ formed silver nanoparticle (Ag NP)-incorporated gallic acid-conjugated chitosan (CHI-G) hydrogels as bio-inspired antimicrobial and tissue adhesive materials. Ag/CHI-G hydrogels were successfully formed by the simultaneous reduction in Ag+ ions with a stable dispersion of Ag NPs. No additional reduction agents or crosslinkers were required to prepare the Ag/CHI-G hydrogels. In addition, the elastic moduli of the Ag/CHI-G hydrogels increased significantly with increasing concentrations of both AgNO3 and CHI-G. Furthermore, the hydrogels exhibited excellent adhesion to the porcine intestinal tissue surfaces. The adhesive Ag/CHI-G hydrogels showed an inhibition of both Escherichia coli and Staphylococcus aureus with no significant cytotoxicity against NIH3T3 and CCD-18Co fibroblasts. Thus, in situ formed Ag/CHI-G hydrogels with adhesive, biocompatible, and antimicrobial properties are expected to be useful for versatile biomedical applications, such as drug delivery depots, tissue engineering hydrogels, and wound dressing materials.