Fabrication of Polymeric Microneedles using Novel Vacuum Compression Molding Technique for Transdermal Drug Delivery

Purpose To demonstrate the feasibility of vacuum compression molding as a novel technique for fabricating polymeric poly (D, L-lactic-co-glycolic acid) microneedles. Methods First, polydimethylsiloxane molds were prepared using metal microneedle templates and fixed in the MeltPrep (R) Vacuum Compression Molding tool. Poly (D, L-lactic-co-glycolic acid) (EXPANSORB (R) DLG 50-5A) was added, enclosed, and heated at 130 degrees C for 15 min under a vacuum of -15 psi, cooled with compressed air for 15 min, followed by freezing at -20 degrees C for 30 min, and stored in a desiccator. The microneedles and microchannels were characterized by a variety of imaging techniques. In vitro permeation of model drug lidocaine as base and hydrochloride salt was demonstrated across intact and microporated dermatomed human skin. Results Fabricated PLGA microneedles were pyramid-shaped, sharp, uniform, and mechanically robust. Scanning electron microscopy, skin integrity, dye-binding, histology, and confocal laser microscopy studies confirmed the microchannel formation. The receptor delivery of lidocaine salt increased significantly in microporated (270.57 +/- 3.73 mu g/cm(2)) skin as compared to intact skin (142.19 +/- 13.70 mu g/cm(2)) at 24 h. The receptor delivery of lidocaine base from microporated skin was significantly higher (312.37 +/- 10.57 mu g/cm(2)) than intact skin (169.68 +/- 24.09 mu g/cm(2)) up to 8 h. Lag time decreased significantly for the base (2.24 +/- 0.17 h to 0.64 +/- 0.05 h) and salt (4.76 +/- 0.31 h to 1.47 +/- 0.21 h) after microporation. Conclusion Vacuum compression molding was demonstrated as a novel technique to fabricate uniform, solvent-free, strong polymer microneedles in a short time.

Automated summary

This study demonstrated that vacuum compression molding is a novel technique for fabricating polymeric microneedles. The fabricated microneedles were pyramid-shaped, sharp, uniform, and mechanically robust. Various imaging techniques confirmed the formation of microchannels, and the release of lidocaine from the microneedles was significantly increased.