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

Abstract

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 day (sun damage). Interestingly, students found higher levels of postillumination radical formation in sunscreen-treated samples, perhaps indicating sunscreen-induced stabilization of these species. Student outcomes included learning how to collect and interpret EPR data, statistical analysis of these data, and the preparation of reproducible biological samples. Students also consulted literature sources to properly display their measurements.

Examining Particle Size of Inorganic Active Ingredients within Sunscreens Using Dynamic Light Scattering

“…31 This laboratory experiment places emphasis on understanding the DLS as the main form of instrumental analysis and, if possible, will allow the use of a second instrument to assist students in understanding conceptually how the DLS works by creating a more complete analysis and comparison as shown in previous educational publications. 1,3,25,32 This experimentation also shows a compar-ison between sunscreen samples and standards: both nanopowder and dispersions.…”

“…Another argument in the use of nanoparticles is the oxidative stress and contribution to reactive oxygen species (ROS) generation and activation of various signal transduction pathways in target cells. 3,56 This is important since the human body needs a way to counteract or detoxify the potential damage through neutralization by antioxidants. 56 Recently, researchers analyzed consumer products (MLPs) such as Henna tattoos, skin-care products, and cosmetics with TiO 2 nanoparticles and found that the nanoparticle did not alter the cytotoxicity profiles of the consumer products' ingredients, and there were no alterations of cellular apoptosis, ROS production, or cellular glutathione content.…”

“…2 Sunscreens are commonly composed of organic active ingredients that have the ability to absorb radiation and/or inorganic components which can scatter the light's waves. 3 The FDA has since approved 17 active ingredients that can be used in the preparation of sunscreens, ranging from organic filters to metal oxides. 2 Of the 17 FDA approved ingredients, the Environmental Working Group (EWG) claims that only 4 of the ingredients (Mexoryl SX, avobenzone, titanium dioxide, and zinc oxide) provide full UV-A protection.…”

“…Sunscreens are commonly composed of organic active ingredients that have the ability to absorb radiation and/or inorganic components which can scatter the light’s waves . The FDA has since approved 17 active ingredients that can be used in the preparation of sunscreens, ranging from organic filters to metal oxides .…”

“…Even though there are various publications of experiments dealing with sunscreen analysis in a teaching lab, there are few laboratory experiments published in the Journal of Chemical Education that have used DLS with consumer and real world samples. ,,,− The majority of those experiments deal with analysis of particle sizing after synthesizing nanoparticles. , Some other publications suggest the use of the DLS as a sophisticated instrumentation technique to analyze nanoparticle dispersion, in conjunction with multiple other instruments, as an inquiry-based approach to teach students about characterization of unrevealed nanoparticles to determine their composition, size, morphology, and surface area. , However, some of these publications focus on multiple instrumentations based on graduate-level content that apply the DLS as a supplemental portion of the overall experimentation . This laboratory experiment places emphasis on understanding the DLS as the main form of instrumental analysis and, if possible, will allow the use of a second instrument to assist students in understanding conceptually how the DLS works by creating a more complete analysis and comparison as shown in previous educational publications. ,,, This experimentation also shows a comparison between sunscreen samples and standards: both nanopowder and dispersions.…”