Fabrication and Evaluation of Glabridin Tip-loaded Dissolving Microneedles

Background: The clinical application of glabridin in treating skin diseases has been constrained by the limitations of its poor chemical stability and low skin permeability. Objective: Here, we describe Tip-loading Dissolving Microneedles (TDMNs) encapsulating drugs only in the tips of needles for glabridin delivery with improved stability and skin permeability. Methods: The TDMNs fabricated by solvent casting technique had sufficient mechanical strength to penetrate through the excised rat's skin without fracture. Drug delivery efficiency and drug residual in the skin of TDMNs were 63.16% and 49.28%, respectively. Glabridin encapsulated in the tips of TDMNs was effectively delivered into the abdominal skin of rat, and the in vivo delivery efficiency was inversely proportional to the drug doses. Results: Transepidermal Water Loss (TEWL) significantly increased to 34.80 g/m2·h after the application of TDMNs and returned to normal levels (11.31 g/m2·h) after 8 h, indicating that the TDMNs were well tolerated. The stability of glabridin at room temperature was appreciably improved when loaded in TDMNs. Conclusion: These results suggest that intradermal delivery of glabridin by TDMNs is a safe and efficient alternative to currently available routes of administration.