Bioadhesive patches based on carboxymethyl cellulose/polyvinylpyrrolidone/bentonite composites and Soluplus® for skin admninistration of poorly soluble molecules

The skin delivery of poorly soluble drugs represents a problem especially for formulations with limited residence time for which a low amount of drug is released with consequent inefficacy of the therapy. Many purposed approaches suggest the use of nanocarriers as liposomes, micro/nanoparticles or cyclodextrins to solve this problem. This study aims at enhancing the skin delivery of poorly soluble drugs by a simple and scalable formulation. With this aim, a skin self-adhesive flexible and mechanically resistant patch was developed. A composite between sodium carboxymethyl cellulose/polyvinylpyrrolidone and bentonite was prepared and combined to Soluplus®, a co-polymer used to obtain a solid dispersion of poorly soluble drugs. With this objective the molecule β-glycyrrhetinic acid (Gly) was used as model. Two different bentonites, having different morphologies (flake-shaped and spherical) and dimensions (micrometric and nanometric), were assayed to evaluate their effect on patch final properties. Patches containing bentonite/Soluplus® (ratio 1:1 wt./wt.) were the most promising as they feature i) good deformability and suitable mechanical properties to adapt to large deformations during application and use, ii) self-adhesivity to the skin and iii) controlled release. The different morphologies of the chosen bentonites did not produce differences in the final mechanical properties. The amount of Gly released is able to control the growth of S. aureus and Methicillin-Resistant Staphylococcus aureus, bacterial strains involved in many skin infections.