pH-responsive cationic guar gum-based multifunctional hydrogel with silver nanoenzymes: Combined photothermal antibacterial therapy and antioxidant properties for MRSA infected wound healing.

Managing wounds infected with multi-drug-resistant (MDR) bacteria remains a significant public health challenge in clinical settings. While multifunctional hydrogels are commonly employed to treat skin infections, there is a scarcity of hydrogels that effectively combine cationic guar gum (CG) with both potent antimicrobial and safe therapeutic actions. This study introduces a novel pH responsive, dual-dynamically crosslinked hydrogel (CFC-PDA/Ag), synthesized by crosslinking CG with polydopamine (PDA)-coated silver nanozymes (PDA/PM-AgNPs). The formulated hydrogel demonstrates pH-sensitive peroxidase (POD)-like activity and notable photothermal conversion efficiency (58.39 ± 2.45 %). It exhibits optimal mechanical properties (elastic modulus, G': 0.99 kPa; viscous modulus, G": 0.26 kPa), excellent injectability, self-healing within one minute, and efficient pH -responsive nanozyme release (82.64 % at pH 7.4 and 95.73 % at pH 6.4), enabling targeted bactericidal and anti-inflammatory effects. Extensive in vitro assessments confirm the hydrogel's robust photothermal properties (temperature range: 25-55 °C), outstanding antibacterial activity (kill rates of 99.12 ± 0.26 % against MRSA and 97.57 ± 1.22 % against E. coli), and effective free radical scavenging capabilities (DPPH: 91.25 ± 1.55 %, PTIO: 63.66 ± 8.32 %). In vivo studies on rat models with full-thickness MRSA-infected skin wounds demonstrated that CFC-PDA/Ag effectively eradicates MRSA, reduces inflammation, and enhances angiogenesis and collagen deposition, significantly accelerating the wound healing process. Collectively, these findings underscore the transformative potential of CFC-PDA/Ag hydrogel as an innovative therapeutic platform for treating wounds infected with MDR pathogens.