Fabrication of Dissolving Microneedles with Thermal-Responsive Coating for NIR-Triggered Transdermal Delivery of Metformin on Diabetic Rats

This study described near-infrared (NIR) light-responsive polymer-nanodot composite microneedles (MNs) used for on-demand transdermal drug delivery. Bismuth (Bi) nanodots stabilized by poly(vinylpyrrolidone) (PVP) as a photothermal conversion agent and metformin as an antidiabetic drug were introduced into the dissolving MNs coated with lauric acid (LA). When the MNs were irradiated with NIR light, light-to-heat transduction induced by the Bi nanodots caused the LA to melt. As a result, the polymer matrix was dissolved after absorbing the interstitial fluid, enabling the encapsulated metformin release from the MNs into skin tissue. Compared with subcutaneous injection of metformin, the administration using the Bi nanodots-induced NIR responsive MNs developed in the current research exhibited a remarkable hypoglycemic effect in vivo. This work indicates that the as-fabricated Bi nanodot-induced NIR responsive and LA-coated MNs have potential applications in diabetes treatment. Additionally, these artificial MNs also present a promising platform for delivering other therapeutic drugs.