Modulating microneedles’ array design and application force for personalizing skin permeation using design of experiments

Polymeric microneedle arrays are medical devices composed of micro-scale needles that enhance skin permeation by breaching stratum corneum's integrity and creating microchannels. Morphology as well as dimensional characteristics of these structures, namely height, base width, density of arrays and tip diameter can significantly affect the permeation profile of the active ingredient. Additionally, the force applied during application is also considered a key factor of drug delivery. Therefore, within the concept of personalizing the rate and amount of drug permeated through skin, a screening of the aforementioned factors was performed. Specifically, microneedles of various geometries and dimensions were prepared and evaluated with regards to their dimensional accuracy, insertion depth and drug permeation. For this purpose, Ropinirole Hydrochloride (RopHCl) was utilized as model drug due to its hydrophilic nature. In more detail, ten microneedle morphologies were evaluated in relation to their effect in the drug delivered, while a Definitive Screening Design (DSD) was implemented to screen the effect of the microneedle dimensional characteristics in the arrays' performance. Overall, significant differentiations between the microneedles shapes were observed across the permeation profiles while height, interspacing distance and insertion force were the main factors revealed as significant by the experimental design applied. Regarding base width, although it does not directly influence drug permeation, it affects the mechanical rigidity. It can be thus concluded that drug permeation through skin can be effectively personalized by tuning the microneedle array properties, while keeping a constant microneedle composition.