Bletilla striata polysaccharide microneedles with astragaloside Ⅳ loaded ZIF-8 nanoparticles for wound healing and anti-scar treatment

Pathological scars (PS), a prevalent complication following wound healing, can lead to disfigurement, itching, pain, and skin dysfunction, which severely degrade patients' quality of life. Conventional single-treatment approaches struggle to concurrently resolve the clinical dilemma between achieving rapid wound healing and precisely suppressing scar formation. Thus, a Bletilla striata polysaccharide (BSP) microneedle patch (BSP-As@ZIF-8 MNs) with astragaloside Ⅳ (As) encapsulated in zeolite imidazolate framework (ZIF-8) was designed and prepared. BSP-As@ZIF-8 MNs can intelligently respond to pH variations at different stages of wound healing through ZIF-8 nanoparticles to enable controlled release of As. When further combined with BSP, they achieve precise synergistic therapy by promoting early-stage wound healing and providing late-stage anti-scarring effects. The experimental results showed that the BSP-As@ZIF-8 MNs had good mechanical properties and skin penetration, and exhibited excellent antibacterial ability and good biosafety. Drug release results showed that BSP-As@ZIF-8 MNs accelerated the release of As as the pH decreased. Further experiments indicated that BSP-As@ZIF-8 MNs promoted rapid wound healing by activating VEGF and inhibiting TNF-α, and prevented scar formation by reducing TGF-β1, decreasingthe proportion of type I/III collagen, and regulating the collagen deposition in the TGF-β1/Smads pathway. In conclusion, BSP-As@ZIF-8 MNs can synergistically promote wound healing and prevent scar formation, providing a promising drug delivery strategy for wound repair and scar prevention.