Fabrication of Dissolving Polymer Microneedles for Controlled Drug Encapsulation and Delivery: Bubble and Pedestal Microneedle Designs

Dissolving microneedle patches offer promise as a simple, minimally invasive method of drug and vaccine delivery to the skin that avoids the need for hypodermic needles. However, it can be difficult to control the amount and localization of drug within microneedles. In this study, we developed novel microneedle designs to improve control of drug encapsulation and delivery using dissolving microneedles by (i) localizing drug in the microneedle tip, (ii) increasing the amount of drug loaded in microneedles while minimizing wastage, and (iii) inserting microneedles more fully into the skin. Localization of our model drug, sulforhodamine B in the microneedle tip by either casting a highly concentrated polymer solution as the needle matrix or incorporating an air bubble at the base of the microneedle achieved approximately 80% delivery within 10 min compared to 20% delivery achieved by the microneedles encapsulating nonlocalized drug. As another approach, a pedestal was introduced to elevate each microneedle for more complete insertion into the skin and to increase its drug loading capacity by threefold from 0.018 to 0.053 μL per needle. Altogether, these novel microneedle designs provide a new set of tools to fabricate dissolving polymer microneedles with improved control over drug encapsulation, loading, and delivery.