Chitosan-decorated polystyrene-b-poly(acrylic acid) polymersomes as novel carriers for topical delivery of finasteride

In view of the fact that the oral administration of finasteride (FIN) has resulted in various undesirable systemic side effects, the topical application of polystyrene and poly(acrylic acid)-based polymersomes (underexplored system) was investigated. Undecorated PS139-b-PAA(17) and PS404-b-PAA(63) vesicles (C3 and C7, respectively) or vesicles decorated with chitosan samples of different molecular weight (C3/CS-oligo, C7/CS-oligo, C3/CS-37 and C7/CS-37) were prepared by the co-solvent self-assembly method and characterized by small-angle X-ray scattering, transmission electron microscopy and dynamic light scattering techniques. In vitro release experiments and ex vivo permeation using Franz diffusion cells were carried out (through comparison with hydroethanolic finasteride solution). The ideal system should provide high finasteride retention in the dermis and epidermis while allowing some control of the drug release. The particle size and in vitro release were negatively correlated with the permeation coefficient and skin retention in both the epidermis and dermis. The findings that the longest lag time was obtained for the hydroethanolic drug solution and lowest permeation for the systems able to release the drug faster support the hypothesis that nanostructured systems may be required to enhance the penetration and permeation of the drug. Chitosan-decorated polymersomes interacted more strongly with the skin components than non-decorated samples, probably due to the positive surface charge, which increased the FIN retention and reduced the lag time. C7 polymersomes decorated with chitosan were more appropriate for topical applications (high retention in the dermis and epidermis and controlled drug delivery). (C) 2013 Elsevier B.V. All rights reserved.