Bilayer microneedles based on Bletilla striata polysaccharide containing asiaticoside effectively promote scarless wound healing

The repair of wounds is essential for overcoming injuries, but the process often leads to scars, and the formation mechanism is unclear. Interestingly, Bletilla striata polysaccharide (BSP) is a procoagulant and has anti-inflammatory properties to promote wound healing, which has great research value for scarless wound healing. Herein, we developed a transdermal drug delivery system of BSP/chitosan (CS) composite bilayer dissolvable microneedles (CS-AS-BSP MNs) containing asiaticoside (AS) based on a centrifugation method with a polydimethylsiloxane mould that fulfilled the requirements of wound healing and achieved a scar-free effect. The drug release results showed that this system improved the solubility of AS and maintained the stable release of the drug for a long time. Further experiments indicated that CS-AS-BSP MNs had a good antibacterial effect and reduced the proliferation of human scar fibroblasts. The wound healing effect of CS-AS-BSP MNs was evaluated in an experimental full-thickness-wound rat model, which demonstrated that the covered wound healed completely without scars within 3 weeks. Furthermore, CS-AS-BSP MNs downregulated TGF-β1 and COL Ⅰ, which are fibrosis-related genes, to inhibit scarring. In brief, this study provides a new strategy for meeting the clinical requirements of effective scarless wound dressings.