TiO₂ nanoparticles as an effective UV-B radiation skin-protective compound in sunscreens

Protecting human skin against harmful UV-B radiation coming from the sun is currently a problem. Due to the decreased thickness of the ozone layer, a more dangerous amount of UV-B light reaches the surface of our planet. This causes increased frequency of skin diseases. Titanium dioxide (TiO₂) fine particles are embedded with sunscreens into the skin to effectively attenuate UV-B radiation. This study evaluates the most appropriate size of such particles assuming they are spheres. The distribution of TiO₂ particles within the skin, achieved with topically applied sunscreens, is determined experimentally by the tape-stripping technique. Computer code implementing the Monte Carlo method is used to simulate photon migration within the plain 20 νm thick horny layer matrix partially filled with nano-sized TiO₂ particles. Dependences of harmful UV-B radiation of 307-311 nm absorbed by, backscattered from and transmitted through the horny layer on the concentration of TiO₂ particles are obtained and analysed. As a result, particles of 62 nm are found to be the most effective in protecting skin against UV-B light.