Effect of calcium carbonate nanoparticles on in vitro photoprotection efficiency of physical sunscreens

Abstract

Physical sunscreens are safer, more photostable and broader spectral protection but exhibit lower SPF than chemical sunscreens. In this study, calcium carbonate nanoparticles were combined with both titanium dioxide and zinc oxide to improve UV protection efficiency. Speed and duration of high speed disperser were varied to investigate suitable dispersing condition in dimethicone oil. The results showed that speed of 2000 rpm and duration of 10 minutes was the optimal condition.

Concentrations of physical sunscreens and calcium carbonate were varied to study the UV improving protection using UV-Visible spectrophotometer. It was found that addition of calcium carbonate can improve UV absorption in every physical sunscreen concentrations. The enhancing results were confirmed by evaluating the sun protection factor SPF and UVA protection factor UVA-PF values using SPF analyzer. Titanium dioxide combined with calcium carbonate resulted in synergistic effect on UV protection whereas the combination of zinc oxide and calcium carbonate exhibited only additive effect. Therefore, titanium dioxide combined with calcium carbonate was chosen to be formulated in water in oil (w/o) and oil in water (o/w) emulsions to investigate for suitable emulsion type. The results showed that w/o had better SPF and UVA-PF values than o/w (p<0.05). In conclusion, calcium carbonate nanoparticles can be used as photoprotection enhancer for both physical sunscreens. The enhancement was especially high for titanium dioxide where it can reduce the level of titanium dioxide used in the formulation.