Process optimization and photostability of silymarin nanostructured lipid carriers: effect on UV-irradiated rat skin and SK-MEL 2 cell line

The objective of the present work was to formulate a novel stable delivery system which would not only overcome the solubility issue of silymarin, but also help to increase the therapeutic value by better permeation, anticancer action and reduced toxicity. This was envisaged through the recent developments in nanotechnology, combined with the activity of the phytoconstituent silymarin. A 2 full factorial design based on three independent variables was used for process optimization of nanostructured lipid carriers (NLC). Developed formulations were evaluated on the basis of particle size, morphology, in vitro drug release, photostability and cell line studies. Optimized silymarin-NLC was incorporated into carbopol gel and further assessed for rheological parameters. Stable behaviour in presence of light was proven by photostability testing of formulation. Permeability parameters were significantly higher in NLC as compared to marketed phytosome formulation. The NLC based gel described in this study showed faster onset, and prolonged activity up to 24 h and better action against edema as compared to marketed formulation. In case of anticancer activity of silymarin-NLC against SK-MEL 2 cell lines, silymarin-NLC proved to possess anticancer activity in a dose-dependent manner (10–80 μM) and induced apoptosis at 80 μM in SK-MEL 2 cancer cells. This work documents for the first time that silymarin can be formulated into nanostructured lipoidal carrier system for enhanced permeation, greater stability as well as anticancer activity for skin.