Bifunctional Aloe-Birch Extracts for Green Silver Nanoparticle Synthesis and Synergistic Antimicrobial Microneedles Toward Infected Wound Healing

Plant-mediated green synthesis of silver nanoparticles (AgNPs) predominantly relies on single botanical sources, constraining reduction efficiency and forfeiting the therapeutic potential of residual biomass. This study employed aloe vera and birch bark extracts as reducing agents. A combination of single-factor analysis and response surface methodology was employed to prepare monodisperse 30 nm AgNPs (with a Zeta potential of −35.3 mV and confirmed by XPS as metallic Ag0). It was loaded into carboxymethyl chitosan-vanillin-polyvinyl alcohol (CVP) gel microneedles using the vacuum casting method. The mechanical strength of these microneedles reaches 0.302 N/needle, exceeding the skin penetration threshold. Throughout the entire preparation process, both its Ag0 chemical state and crystal structure were maintained (by FT-IR and XRD). The MIC values of AgNPs@CVP against four pathogens ranged from 0.977 to 7.813 μg/mL, with a biofilm disruption rate exceeding 70%, and demonstrated excellent biocompatibility (hemolytic rate < 1.6%, cell survival rate > 80%). In a rat wound infection model, high-dose microneedle therapy reduced the residual wound area to 10.9% by day 9. This strategy inhibited the secretion of TNF-α and IL-6 while promoting epithelial regeneration, angiogenesis, and collagen deposition. This bifunctional Aloe-Birch strategy converges green nanomaterial synthesis with therapeutic delivery within a single bio-based platform, advancing sustainable nanomedicine paradigms and providing a resource-efficient blueprint for clinical infectious wound management.