Development, characterization, and evaluation of sunscreen cream containing solid lipid nanoparticles of silymarin

Most of the sunscreen formulations mainly contain chemicals or synthetic molecules. Nowadays, researchers are mainly focussing on herbal formulations due to toxicity of the synthetic molecules. Silymarin is a natural flavonoids having excellent antioxidant properties. Solid lipid nanoparticles are novel drug carriers which improve the drug stability and tolerance effect and also enhance the permeation effect.

This study aimed at the preparation of solid lipid nanoparticles containing silymarin that will be incorporated into a sunscreen cream and determine its sun protection factor.

The solid lipid nanoparticles were prepared by micro-emulsion method; here, the glyceryl monostearate was used as lipid, and Tween 80 was used as an emulsifier. The solid lipid nanoparticles were evaluated for drug entrapment, particle size and morphology, zeta potential, and polydispersity index. The dispersion was formulated into sunscreen cream and evaluated for various parameters, such as extrudability, viscosity, spreadability, drug content, in vitro drug release, ex vivo permeation of drug, in vitro and in vivo sun protection factor determination, in vivo skin irritation test, and accelerated stability studies.

The results suggested that as the concentration of emulsifier increased, the entrapment efficiency of silymarin increased. In vitro and in vivo sun protection factor determination showed that SPF of 13.80 and 14.1, respectively. Stability studies were performed under accelerated conditions, and it did not show any appreciable change in parameters.

These results indicated that the sunscreen containing silymarin solid lipid nanoparticles exhibited better photoprotective action.