Dissolving microneedles loaded with chitosan oligosaccharides and gallic acid-modified ε-poly-L-lysine for the combined antibacterial and anti-inflammatory therapy of acne vulgaris.

Acne is a chronic skin disorder closely associated with the over-proliferation of P. acnes within hair follicles. To avoid the overuse of antibiotics and address the low efficiency of conventional transdermal drug delivery, this study reported a chitosan oligosaccharide/gallic acid-modified ε-poly-L-lysine/polyvinyl alcohol microneedle (CEGP MNs) patch for acne treatment. The patch possessed sufficient needle length (600 µm) and mechanical strength (0.8 N per needle) to penetrate the stratum corneum and dissolve rapidly in the dermis, thereby releasing the active ingredients COS and EPL-GA. Experiments demonstrated that COS and EPL-GA effectively kill bacteria through their enhanced antibacterial action, thus alleviating acne-related inflammation. Furthermore, owing to the antioxidant and anti-inflammatory properties of GA, CEGP MNs significantly reduced the expression levels of TNF-α, IL-6, and IL-1β. Meanwhile, CEGP MNs up-regulated the expression of IL-10 and maintained the VEGF at a moderate level to create favorable conditions for the acne repair phase, helping to reduce pigmentation and prevent scar formation. Consequently, in a severe acne mouse model induced by P. acnes, the biocompatible CEGP MNs exhibited promising therapeutic effects. This study proposes an effective acne treatment strategy based on the transdermal delivery of natural compounds.