Microneedle array with a pH-responsive polymer coating and its application in smart drug delivery for wound healing

For successful wound treatment, therapeutics must be delivered directly to the wound. Various issues restrict the delivery of antibiotics to wounds, including the barrier mannered by necrotic tissue and biofilms, which create an extracellular polymeric layer that impedes the efficient administration of therapeutics. For achieving break of the necrotic tissue barrier and biofilm, in addition, improving antibiotics penetration through a painless administration, we fabricated porous polymer coatings on microneedles (MNs) which had the ability of automatic “release” therapeutics in response to wound pH conditions. In the pores of the porous polymer film, the model drug was packed using aqueous gelatin porogen, and the porous layer was coated with a Eudragit S100 film to cap the pores to prevent drug leakage and provide a wound pH-responsive drug release. By combining the advantages of porous and pH-responsive polymer coatings, the coated MNs exhibited remarkably enhanced therapeutic results. This formulation showed both in vivo (in rats) and in vitro (in phosphate-buffered saline and in porcine skin) wound pH-sensitive drug release with rapid responsiveness. At healthy skin pH (pH 4.5), an insignificant release was noticed for MNs in the test media. However, drug release considerably increased when MNs were exposed to wound pH conditions (pH 7.5). The present study provides proof-of-concept evidence that developed MNs have the potential of enhanced treatment protocol for wound infections with the flexibility of coating materials and antimicrobials and offers significant scope for further variations and advancement.