EPR Dosimetry in Human Fingernail: Ultraviolet-Induced Signals

Abstract

Abstract This manuscript reports on the effect of ultraviolet (UV) and sunlight irradiated fingernail samples by electron paramagnetic resonance (EPR) in Q-band. Two UV-induced signals were identified and studied in detail. The first one labeled as UVIS2, was measured shortly after UVA radiation. The parameters of the UVIS2 are very similar to those from the previously identified radiation-induced signal RIS2. The second identified UV-induced signal, labelled UVIS5, is similar in behavior to the radiation-induced signal RIS5 and superimposed on the background signal labelled BKS. UVIS5 is stable over time and is induced by UV irradiation and sunlight. This signal is similar to the BKS endogenous signal that is attributed to anionic semiquinone radicals generated by degradation of the dihydroxyphenylalanine (DOPA) molecules. The uncontrolled sunlight exposure of fingernails can be responsible for contributing to the known interpersonal variability of the BKS, resulting from different exposures times to sunlight. The endogenous signal BKS and the UVIS5 are two components of the same signal, but of different origins. The origin of the BKS has not yet been fully identified. In principle, UVIS5 can potentially be used as an individual biomarker of the dose from UV-irradiation.