Fabrication of Poly Lactic-<i>co</i>-Glycolic Acid Microneedles for Sustained Delivery of Lipophilic Peptide-Carfilzomib

Transdermal drug delivery (TDD) is an attractive route of administration, providing several advantages, especially over oral and parenteral routes. However, TDD is significantly restricted due to the barrier imposed by the uppermost layer of the skin, the stratum corneum (SC). Microneedles is a physical enhancement technique that efficiently pierces the SC and facilitates the delivery of both lipophilic and hydrophilic molecules. Dissolving microneedles is a commonly used type that is fabricated utilizing various biodegradable and biocompatible polymers, such as polylactic acid, polyglycolic acid, or poly(lactide-<i>co</i>-glycolide) (PLGA). Such polymers also promote the prolonged release of the drug due to the slow degradation of the polymer matrix following its insertion. We selected carfilzomib, a small therapeutic peptide (<i>M</i>_W: 719.924 g/mol, log <i>P</i> 4.19), as a model drug to fabricate a microneedle-based sustained delivery system. This study is a proof-of-concept investigation in which we fabricated PLGA microneedles using four types of PLGA (50-2A, 50-5A, 75-5A, and 50-7P) to evaluate the feasibility of long-acting transdermal delivery of carfilzomib. Micromolding technique was used to fabricate the PLGA microneedles and characterization tests, including Fourier transform infrared spectroscopy, insertion capability using the skin simulant Parafilm model, histological evaluation, scanning electron microscopy, and confocal microscopy were conducted. <i>In vitro</i> release and permeation testing were conducted in vertical Franz diffusion cells. <i>N</i>-methyl pyrrolidone was utilized as the organic solvent and microneedles were solidified in controlled conditions, which led to good mechanical strength. Both <i>in vitro</i> release and permeation testing showed sustained profiles of carfilzomib over 7 days. The release and permeation were significantly influenced by the molecular weight of PLGA and the lipophilic properties of carfilzomib.