Comparing Free Radicals in Sunscreen-Treated Pig Skin by Using Electron Paramagnetic Resonance Spectroscopy

Melanoma, a type of cancer that develops in melanocytes, is usually caused by direct exposure of skin to ultraviolet (UV) radiation resulting in cellular damage. In this study, a procedure to determine the effects of various commercial sunscreens with SPF values ranging from 15 to 100 was developed using pig skin to mimic human skin. These sunscreens contain inorganic filters, such as zinc oxide and titanium dioxide; active organic ingredients, such as octocrylene and oxybenzone; or both. As a model for human skin, pig skin was analyzed before and after UV exposure, and the presence of free radicals was measured using electron paramagnetic resonance (EPR) spectroscopy. Using this method, students were able to quantify radical formation following irradiation and use this as a basis to compare the efficacies of sunscreens against UVA. This experiment allowed undergraduate students to characterize a complex chemical process (light-induced radical formation) and relate it to something they experience every da...