Separable Microneedles for Near-Infrared Light-Triggered Transdermal Delivery of Metformin in Diabetic Rats

Near-infrared (NIR) light-triggered and separable segmented microneedles (MNs), consisting of lauric acid and polycaprolactone (LA/PCL) arrowheads and poly(vinyl alcohol) and polycaprolactone (PVA/PVP) supporting bases, have been fabricated. A hypoglycemic drug (metformin) and photothermal conversion factor (Cu7S4 nanoparticles) are encapsulated into LA/PCL arrowheads. Due to the dissolution of soluble supporting bases after the absorption of tissue fluid, the separable MNs arrowheads can be embedded into skin after insertion. Under the NIR-light irradiation, the LA/PCL arrowheads exhibit an excellent thermal-ablation change with a low amount of Cu7S4 nanoparticles (0.1 wt %) due to the low melting point of LA and PCL, thus enabling the release behavior of the encapsulated model drug to be photothermally triggered. Compared to the hypodermic injection of metformin, the thermal ablation of separable MNs triggered by NIR irradiation in the current research exhibit an excellent hypoglycemic effect in vivo. It suggests that the NIR-induced thermal-ablation MNs comprise a prospective transdermal drug-delivery system for the precise control of the timing and dosage of a drug that is dependent on NIR administration.