Amphiphilic gels as a potential carrier for topical drug delivery

This study involves development of amphiphilic gels consisting solely of nonionic surfactants bearing cyclosporine and characterized for microstructure, gelation temperature, and in vitro drug release into dermis. The formulation is nonirritant and suitable for topical application. Gels consisting of cyclosporine were prepared using different methods by mixing the solid gelator (sorbitan or glyceryl fatty acid esters) and the liquid phase (liquid sorbitan esters or polysorbates) and heating them at 60 degrees C to form a clear isotropic sol phase, and cooling this sol phase to form an opaque semisolid at room temperature. Gel microstructure was examined by phase contrast microscopy while gelation temperatures were measured by melting point apparatus and differential scanning calorimetry. These amphiphilic gels were evaluated in vitro for topical as well as transdermal delivery using rat skin mounted in a Franz diffusion cell. Gel microstructures consisted mainly of clusters of tubules of gelator molecules that had aggregated upon cooling of the sol phase, forming a 3D network throughout the continuous phase. The gels demonstrated thermoreversibility with robust gel network. At temperatures near the skin surface temperature, the gels softened considerably and moreover, it facilitated the drug to accumulate in dermis, thus making an ideal delivery vehicle of cyclosporine topically that can be used in treatment of psoriasis. Thus amphiphilic gels were demonstrated as the ideal vehicle for topical use of cyclosporine.