Antimicrobial mechanism study of NIR-activated chitosan-montmorillonite hydrogel and their anti-MDR S. aureus properties in vitro pigskin model

Wound infections caused by surgery, chronic ulcers, or trauma have been a challenge for clinicians, especially multiple resistant bacteria induced by the misuse of antibiotics, which has increased the risk of bacterial infection. It is very urgent to design and develop antimicrobial materials with potential for clinical application against drug-resistant bacterial infections. In this study, a photothermal montmorillonite-chitosan hydrogel system (MNT-CS Gel) was fabricated as a photothermal antimicrobial dressing. This study found for the first time that montmorillonite (MNT) has good photothermal properties and photothermal conversion efficiency under near-infrared (NIR) light, and on this basis, its application research was carried out. The MNT possesses broad-spectrum antibacterial activity with significant inhibitory effects against E. coli and S. aureus, excellent photothermal stability under NIR light. And all the performances were improved after combining with CS-Gel, especially in bacterial adsorption capacity and photothermal performance. Notably, MNT-CS Gel was used as a photothermal antibacterial agent for the first time, and the antibacterial effects in vitro and their mechanisms have been systematically investigated. It was found that the MNT-CS Gel had significant inhibitory and destructive effects on bacteria in an in vitro pigskin model. The MNT-CS Gel could adsorb the bacteria strongly, inhibit bacterial biofilm formation, induced the generation of ROS, destroy the structure of bacteria, and cause the leakage of nucleic acids. The MNT-CS Gel demonstrated good photothermal antimicrobial properties, suggesting that the MNT-CS Gel has potential for clinical hygiene applications.