Gallic acid-grafted chitosan photothermal hydrogels functionalized with mineralized copper-sericin nanoparticles for MRSA-infected wound management.

The management of wounds infected with drug-resistant bacteria represents a significant challenge to public health globally. Nanotechnology-functionalized photothermal hydrogel with good thermal stability, biocompatibility and tissue adhesion exhibits great potential in treating these infected wounds. Herein, a novel photothermal hydrogel (mCS-Cu-Ser) was prepared through in situ mineralization in the hydrogel networks and ion cross-linking driven by copper ions (∼3 mM). Self-assembling polyphosphate sericin nanoparticles (Ser NPs) formed by an ultrasound-assisted anti-solvent method were as mineralization templates and gallic acid-grafted chitosan (mCS) was prepared as the sole matrix. Grafting of polyphenols and cross-linking of copper ions endowed mCS-Cu-Ser with injectable, skin-adhesive and self-healing characteristics. Due to the nonradiative relaxation of Cu electron-hole pairs of copper phosphate on the surface of Ser NPs and the molecular thermo-vibrational effect of the mCS-Cu complex, mCS-Cu-Ser rapidly warmed up to 50 °C within one minute under near-infrared (NIR) irradiation. Integrating such excellent photothermal properties with antimicrobial activity and intracellular reactive oxygen species scavenging from mCS, mCS-Cu-Ser + NIR effectively accelerated methicillin-resistant Staphylococcus aureus (MRSA) infected wound healing. This work develops a novel dressing for the treatment of MRSA-infected wounds and provides some reference for the preparation of multifunctional acid-free chitosan hydrogels.