Photo-Responsive Hydrogel Microneedles With Interlocking Control for Easy Extraction in Sustained Ocular Drug Delivery

Abstract

Microneedle arrays provide a minimally invasive platform for ocular drug delivery. Self-adhesive microneedle arrays, which incorporate barb-like locking features, have been developed to secure the array in place without using any adhesive. However, these locking features may increase extraction forces when removing the microneedle array once the drug delivery is completed. In this study, we demonstrated a photoresponsive hydrogel microneedle array that can self-adhere to the application site upon swelling and can deswell for easy removal when illuminated with light. The photoresponsive hydrogel microneedle arrays were made by a mixture of polyvinyl alcohol and spiropyran-conjugated N-isopropylacrylamide (NIPPAM). Experimental results show a significant decrease in extraction force after the microneedle of 20% spiropyran-conjugated NIPPAM was illuminated with light for 15 min. At the same time, the width of the interlocking feature also deswelled by 20% due to the photoresponsive behavior. However, the addition of the spiropyran-conjugated NIPPAM also weakens the mechanical properties of the microneedle and thus increase in insertion force.