Fabrication of Rapidly Separable Microneedles for Transdermal Delivery of Metformin on Diabetic Rats

In this work, the rapidly separable microneedles (MNs) consisted of needle-tips and supporting bases have been fabricated by a step-by-step coating method. Poly (vinyl alcohol) (PVA) have been used to prepare the needle-tips of MNs in which they are capped on the solvable supporting bases consisted of sodium bicarbonate, poly (vinyl pyrolidone) (PVP), and tartaric acid (TA) (NaHCO₃/PVP/TA). After insertion into the skin, the needle-tips can be separated rapidly from the patches within 90 s due to the generation of air bubbles in the supporting bases by the reaction between NaHCO₃ and TA after absorption of tissue fluid, leading to the needle-tips remaining in the skin tissue. Metformin, a hypoglycemic drug, encapsulated in the needle-tips of MNs can be released due to swelling and decomposition of PVA by the absorption of tissue fluid. To investigate the pharmacological effect via transdermal delivery route, metformin-loaded MNs are applied on the diabetic SD rats induced by streptozotocin (STZ). They exhibit a longer hypoglycemic effect in vivo than that of subcutaneous injection. These results indicated the as-fabricated rapidly separable MNs present a promising platform for transdermal delivery of drugs against diabetic patients.