Non-Invasive Label-Free Imaging of Oxidative Processes in Human Skin

Oxidative processes present across all types of organisms, including humans, cause chemical formation of electron excited species with subsequent endogenous ultra-weak photon emission. Thus, imaging of this endogenous chemiluminescence using ultra-sensitive devices potentially enables label-free monitoring of oxidative stress in optically accessible areas of human body, such as human skin. However, no quantified imaging of oxidative processes in human skin has been performed until now using endogenous chemiluminescence under controlled extent of oxidative stress conditions. Furthermore, the mechanisms and dynamics of endogenous chemiluminescence is not fully explored.Here we demonstrate that different degrees of oxidative processes on skin can be spatially resolved through non-invasive label-free endogenous chemiluminescence imaging in a quantitative manner. Additionally, to obtain insight into the underlying mechanisms, we developed and employed a minimal chemical model of skin based on a mixture of lipid (linoleic acid) / melanin / water to show that it reproduces essential features of the response of a real skin to oxidative stress. Our results contribute to novel non-invasive label-free methods for quantitative monitoring of oxidative processes and oxidative stress.We acknowledge support by the Czech Science Foundation, project no. P102/15-17102S. Authors participate in COST Action BM1309 and bilateral exchange project between Czech and Slovak Academies of Sciences, no. SAV-15-22.