A combined study of skin penetration by confocal Raman spectroscopy and human metabolism: A case of benzophenone-3 in sunscreen

Although numerous experiments on benzophenone-3 (BP3) have shown that it can permeate into the skin, the in vivo penetration situation and urinary metabolic trend have not yet been investigated. In this study, sunscreen containing 5.72% BP3 was selected for human-skin exposure. Confocal Raman was successfully used to investigate in vivo skin penetration of BP3 in sunscreen. During 2 h of skin exposure, the semi-quantitative mean values were 5.50, 13.48, 15.79, and 15.00 mu g/cm(2) after application of sunscreen for 15, 30, 60, and 120 min, respectively, indicating that BP3 penetrated the stratum corneum during 60-120 min. After a single exposure of human limbs, BP3 was quickly metabolized and excreted through urine and reached its peak concentration in the 6th hour, whereas its metabolite 2,4-dihydroxybenzophenone (BP1) reached its peak concentration in the 9th hour. Meanwhile, 6% BP3 and 1% BP1 were excreted through the urine within 48 h, but the concentration of 2,2 '-dihydroxy-4-methoxybenzophenone (BP8) was low, although it varied greatly within 48 h after exposure. During consecutive exposures, a significant correlation (p < 0.05) between BP3 concentration and exposure time was found, indicating that BP3 concentration increased at longer exposure times. Therefore, combining Raman spectroscopy and human sample analysis provided a new way to assess absorption and metabolism of personal care additives in the human body.