A novel sunscreen system based on tocopherol acetate incorporated into solid lipid nanoparticles

Solid lipid nanoparticles (SLN) have been introduced as a novel carrier system for drugs and cosmetics. It has been found that SLN possess characteristics of physical UV-blockers on their own, thus offering the possibility of developing a more effective sunscreen system with reduced side-effects. Incorporation of the chemical sunscreen tocopherol acetate into SLN prevents chemical degradation and increases the UV-blocking capacity. Aqueous SLN dispersions were produced and incorporated into gels, followed by particle size examination, stability testing upon storage and thermoanalytical examination. Investigation of the UV-blocking capacity using different in vitro techniques revealed that the SLN dispersions produced in this study are at least twice as effective as their reference emulsions (conventional emulsions with identical lipid content). Placebo SLN even show greater UV-blocking efficacy than emulsions containing tocopherol acetate as the molecular sunscreen. Incorporation of tocopherol acetate into SLN leads to an overadditive UV-blocking effect. Furthermore, film formation of SLN on the skin and occlusivity were examined. The obtained data show that incorporation of tocopherol acetate into SLN leads to an improved sunscreen and skin care formulation.