Prettypaul, Donald. Photophysics and skin penetration of active agents in a commercial sunscreen and insect repellent. Retrieved from https://doi.org/doi:10.7282/t3-ksyj-9v43
DescriptionThis dissertation is focused on active agents in commercial sunscreen and insect repellent products. It consists of two parts, the first focusing on the photophysics of a sunscreen active agent and the second on the permeation and spatial distribution of the sunscreen active and an insect repellent active when these agents are applied to ex-vivo human skin.
In the photochemistry study, ultrafast spectroscopy was used to study the excited state dynamics of the sunscreen molecule, Bemotrizinol. The work focused on the dissipation rates of the electronic excitation energy in different solvents. To complement the results from time-resolved femtosecond spectroscopy, Hartree-Fock UH/UHF 6-31G* calculations were used to characterize the ground and excited states potential energy surfaces. The results indicate that the excited state deactivation pathway follows a proton coupled electron transfer process which proceeds via a concerted mechanism. The dependencies on solvent polarity, viscosity, and H/D isotope effects, were investigated.
Sunscreen products have been developed to protect skin from ultraviolet (UV) radiation; to achieve adequate protection, the sunscreen must be evenly applied and remain on the surface of the skin. However, skin itself presents a major challenge for application of a uniform film because of its undulating surface. Due to these inherent contours, sunscreen filters may not be distributed evenly during application. Confocal Raman microscopy was utilized to investigate the film properties of a sunscreen formulation when applied to ex-vivo human skin. The results indicate that the presence of a film-forming polymer causes the sunscreen active, Bemotrizinol, to be distributed more homogeneously and to temporally persist on the skin surface.
DEET is the most efficacious and widely-used active ingredient formulated into insect repellent. Confocal Raman microscopy was used to investigate the effect of polymers on the spatial distribution and permeation of DEET following its application to ex-vivo human skin. The results confirm that DEET permeates into the skin; furthermore, it is demonstrated that polymers do affect the permeation process in a variety of potentially important ways.