Synergistic thermoresponsive and photothermal antimicrobial dressing based on bacterial cellulose with surface-grafted PNIPAM and PDA-coated silver nanoparticles for chronic wound treatment

Chronic wounds pose significant challenges in clinical treatment due to persistent inflammation, bacterial infections, and prolonged healing cycles. The development of smart dressings with moisture absorption, antibacterial properties, and stimulus responsiveness is particularly important. This work addresses the issues of low rehydration rate, lack of antibacterial activity in bacterial cellulose (BC) films, the complexity of traditional silver nanoparticle (AgNPs) preparation processes, and the varying hydrophilicity/hydrophobicity requirements of dressings at different stages of wound healing. Through a multi-level structural design, a photothermal-thermoresponsive synergistic intelligent antibacterial material was successfully constructed. Firstly, the introduction of glycerol (Gly) as a plasticizer significantly improved the rehydration rate, water vapor permeability, and flexibility of BC films. To endow the dressing with antibacterial properties, the natural antibacterial agent berberine (Ber) was introduced, and the synergistic effect of polydopamine (PDA) and polyethyleneimine (PEI) enabled the in-situ reduction and uniform loading of AgNPs under mild conditions, thereby achieving broad-spectrum antibacterial properties. The outer layer was grafted with thermoresponsive poly(N-isopropylacrylamide) (PNIPAM), leveraging its lower critical solution temperature (LCST) to meet the varying hydrophilicity/hydrophobicity requirements of dressings at different stages of wound healing. Simultaneously, PNIPAM coating effectively regulated the photothermal conversion efficiency of PDA and prevented the early rapid release of silver ions. The antioxidant capacity of Ber not only inhibited the oxidative deactivation of AgNPs but also effectively cleared reactive oxygen species (ROS) generated during wound healing and photothermal processes, thereby reducing tissue oxidative damage. Based on the synergistic antibacterial effects of Ber and AgNPs, the composite films achieved maximum inhibition zones of 4.2 ± 0.12 mm, 5.4 ± 0.16 mm, 1.9 ± 0.04 mm and 1.6 ± 0.04 mm against E. coli , S. aureus , P. aeruginosa and MRSA respectively. The material combines moisture absorption and permeability, biocompatibility, and long-term antibacterial performance, along with environmentally responsive controlled drug release and ROS clearance functions, offering a new solution for chronic wound treatment and promoting the innovative development of smart wound dressings.