Dual-Drug Chitosan Hydrogel Loaded with Metformin and Cefazolin for Antibacterial, Anti-Inflammatory and Antioxidant Treatment of Drug-Resistant Bacteria-Infected Skin Wounds

Bacterial-infected skin wounds, especially those caused by drug-resistant pathogens accompanied by persistent inflammation, remain a major clinical therapeutic challenge. Rising antimicrobial resistance compromises the therapeutic effect of conventional single-agent antibiotics, creating an urgent demand for novel wound therapeutics that integrate bactericidal potency, immunomodulation and tissue regeneration capacity. In this work, an injectable multifunctional chitosan-based hydrogel (C@MC) was developed, which simultaneously incorporates metformin hydrochloride (as a potential antibiotic adjuvant) and cefazolin sodium (as a β-lactam class antibacterial drug). The optimized C@MC possesses interconnected three-dimensional pores with an initial storage modulus of ~0.83 kPa (C@MC360), featuring desirable mechanical strength, injectability, tissue adhesion and dual pH/glucose-responsive sustained drug release. In vitro evaluations revealed the dose-dependent bactericidal activity of C@MC against Staphylococcus aureus (S. aureus), Escherichia coli (E. coli) and New Delhi metallo-β-lactamase-1-producing E. coli (NDM-1 E. coli, resistant bacteria). The highest drug-laden group nearly eliminated all wound bacteria in vitro. It scavenged reactive oxygen species (ROS) to lower cellular MDA levels and suppress pro-inflammatory TNF-α and IL-6 in LPS-stimulated RAW 264.7 macrophages. In full-thickness mouse wounds infected with NDM-1 E. coli, C@MC360 achieved nearly complete wound closure, with only a 4.2% residual wound area on day 14, accompanied by suppressed inflammatory infiltration and accelerated wound regeneration. This dual-drug hydrogel integrates antibiotic potentiation, anti-inflammation and antioxidation, providing an intervention regimen for skin wounds infected with drug-resistant bacteria.