Photostability and stability over time of retinyl palmitate in an O/W emulsion and in SLN introduced in the emulsion

Solid lipid nanoparticles (SLNs) have been introduced as a novel carrier system for drugs and cosmetics. It has been found that SLNs themselves show physical UV-blocking action. Cetyl palmitate, glyceryl behenate, and palmitic acid SLNs, all loaded with retinyl (vitamin A) palmitate, were prepared and introduced in an O/W emulsion. SLNs in O/W emulsion protect retinyl palmitate from the photo degradation induced by UVA and UVB radiation. This effect is probably due to the light-scattering properties of SLN. Nanoparticles also protect vitamin A palmitate from thermal degradation. DSC thermal analytical examination, Z potential determination, and particle size measurement confirmed the solid character of the nanoparticles and the encapsulation of retinyl palmitate, their easy dispersion due to their negative charge on the surface, and their mean diameters in the nanometer range.