A pH-Responsive Core-Shell Microneedle Patch with Self-Monitoring Capability for Local Long-Lasting Analgesia

Postoperative pain, as a common and significant healthcare issue, has always been the focus of attention in the field of anesthesia for its control and treatment. In the present study, a pH-responsive microneedle (MN) patch is developed for sustained incisional analgesia after surgery. The MN patch has a 10 x 10 MN array within 0.5 cm2 area, and each MN features a complete core-shell structure, with a needle height of approximate to 850 mu m. Upon application, the MNs fully implant in the skin within 15 min due to the rapid dissolution of the water-soluble backing layer. The acidic microenvironment at the surgical site (pH 6.8-7.0) interacts with the pH-reactive medium in the MN shell, triggering the shell rupture. This process enables the smooth release of encapsulated local anesthetic drug (Ropivacaine, Rop) microcrystals, extending local anesthesia duration to over 72 h at a drug concentration of 100 mg mL-1. Additionally, the MN patch intelligently modulates drug release based on the postoperative pain behavior, which correlates with the pH value of the surgical incision microenvironment. This responsive feature results in a prolonged and personalized analgesic effect, addressing the limitations of existing invasive treatments in postoperative pain management. In this study, a pH-responsive microneedle (MN) patch with self-monitoring capabilities is engineered for long-lasting analgesia. The MN patch developed in this study holds a great potential in the fields of long-lasting analgesia and postoperative pain management. It paves the way for the refinement and advancement of biomaterials in traditional analgesic approaches.image