Microneedle ocular patch: fabrication, characterization, and ex-vivo evaluation using pilocarpine as model drug

Context: Enhacing the ocular bioavailability of drugs after their topical application is a challenge.Objective: The objective of the study was to design, fabricate, and investigate the effectiveness of microneedle ocular patch (MOP) in delivering the model drug, pilocarpine HCl across the corneal membrane.Methods: MOP mimicked commercially available contact lens design elements having a diameter of 14.20 mm and a sagittal height of 3.85 mm with a convex curvature. The base of this patch contained an array of 25 pyramid-shaped microneedles measuring 521 ± 10 µm in length. Pilocarpine loaded MOP was prepared by micromolding technique using dissolvable polyvinyl alcohol and polyvinyl pyrrolidone matrix. MOP was characterized for physical and mechanical properties using a stereomicroscope, scanning electron microscope, and texture analyzer.Results: Histological examination after MOP application on excised human cornea showed penetration of microneedles with a required insertional force of 1.04 ± 0.17 N. Flux of pilocarpine across excised cornea was significantly (p < 0.05) greater after application of MOP (704 ± 149 µg/cm²/h) compared with solution formulation (188 ± 24 µg/cm²/h). Ex-vivo pilocarpine permeation study in porcine eye globe revealed significantly (p < 0.05) greater availability in aqueous humor within 30 min of application of MOP (249 ± 85 µg/ml) compared with solution formulation (46 ± 9 µg/ml).Conclusion: MOP can be developed as a potential ophthalmic drug delivery system.