Self-Adhesive Microneedles with Interlocking Features for Sustained Ocular Drug Delivery

The interests in sustained ocular drug delivery have grown rapidly in recent years, with hope to replace repeated intravitreal injections. Microneedles (MNs), which are minimally invasive, have been shown to be a feasible vehicle for sustained drug delivery. However, securing an MN patch in the eye remains challenging. In this study, a new design of hydrogel MNs with interlocking features to achieve self-adhesion is proposed. Upon swelling, the swollen interlocking features help secure the MNs in place. A new molding process is developed to fabricate MNs with interlocking features that can cause issues when demolding using the regular micromolding process. MNs with two different interlocking feature designs are used in this study and are made with polyvinyl alcohol. MNs with the interlocking features show an 80% increase in adhesion strength and a small amount of increase in penetration force, in comparison to MNs without any feature. The experiments are performed using both a sclera-mimicking phantom and ex vivo eyes harvested from rabbits and are shown to have comparable results. This study demonstrates the feasibility of incorporating interlocking features to MNs to achieve self-adhesion that can enable sustained drug delivery via MNs.