ROS-Responsive Double-Layer Microneedles Enable Sequential Antibacterial and Immunomodulatory Therapy for Infected Wound Healing

<b>Background:</b> The healing of chronically infected wounds is severely hindered by persistent inflammation, bacterial infection, and oxidative stress, posing great challenges to clinical therapy. To address these challenges, we designed a multifunctional dual-layer microneedles patch (MN@DOX+RES) featuring reactive oxygen species (ROS) responsiveness and dual drug delivery capabilities. This patch is engineered to deliver synergistic antibacterial, anti-inflammatory, and antioxidant effects, thereby promoting the healing of infected wounds. <b>Methods:</b> The dual-layer microneedles patch comprises a rapidly dissolvable HA backing layer loaded with DOX and a ROS-responsive tips layer composed of a crosslinked AHA-PBA/PVA matrix that encapsulates water-soluble RES inclusion complexes. A series of <i>in vitro</i> experiments was conducted to evaluate the mechanical strength, biocompatibility, antibacterial activity against <i>Staphylococcus aureus</i> and <i>Escherichia coli</i>, antioxidant performance, and macrophage polarization. <i>In vivo</i> evaluations were performed on rat models with infected skin wounds. <b>Results:</b> The MN@DOX+RES microneedles exhibited strong skin penetration ability and excellent mechanical strength. It significantly inhibited bacterial growth, efficiently scavenged free radicals, reduced intracellular ROS levels, and enhanced M2 macrophage polarization. <i>In vivo</i>, the patch accelerated wound closure, suppressed the inflammatory cytokine IL-6, enhanced IL-10 expression, and activated the Keap1/Nrf2/HO-1 antioxidant signaling pathway. <b>Conclusions:</b> This study proposes an innovative therapeutic strategy that combines dual-drug delivery, oxidative microenvironment regulation, and immune modulation to promote the healing of chronic infected wounds. The MN@DOX+RES microneedles system demonstrates great potential in overcoming clinical challenges associated with infection, inflammation, and the limitations of conventional therapeutic approaches.