Effect of multiple scattering of light by titanium dioxide nanoparticles implanted into a superficial skin layer on radiation transmission in different wavelength ranges

The propagation of radiation in different spectral ranges in a superficial skin layer partially filled with titanium dioxide nanoparticles at the volume concentration 0.67% – 2.25% is simulated by the Monte-Carlo method. This volume concentration corresponds to the maximum admissible concentrations of particles that most efficiently attenuate radiation in the independent scattering regime. The transmission of radiation at 307, 400, and 500 nm in a 20-μm thick skin layer is simulated and the effect of nanoparticles on the contributions from photons of different scattering orders to transmission is considered. It is shown that the administration of nanoparticles results in the broadening of the scattering-order distribution of photons propagated through the skin layer and the shift of the maximum of this distribution in the direction of a greater number of scattering events at wavelengths 400 and 500 nm, the effect being more pronounced at 400 nm. The increase in the scattering order elongates photon trajectories in the medium and enhances diffusely scattered radiation, thereby reducing transmission.