Multiple spatially resolved reflection spectroscopy for in vivo determination of carotenoids in human skin and blood

Non-invasive measurement of carotenoid antioxidants in human skin is one of the important tasks to investigate the skin physiology in vivo. Resonance Raman spectroscopy and reflection spectroscopy are the most frequently used non-invasive techniques in dermatology and skin physiology. In the present study, an improved method based on multiple spatially resolved reflection spectroscopy (MSRRS) was introduced. The results obtained were compared with those obtained using the ‘gold standard’ resonance Raman spectroscopy method and showed strong correlations for the total carotenoid concentration (R = 0.83) as well as for lycopene (R = 0.80). The measurement stability was confirmed to be better than 10% within the total temperature range from 5 °C to + 30 °C and pressure contact between the skin and the MSRRS sensor from 800 Pa to 18 000 Pa. In addition, blood samples taken from the subjects were analyzed for carotenoid concentrations. The MSRRS sensor was calibrated on the blood carotenoid concentrations resulting in being able to predict with a correlation of R = 0.79. On the basis of blood carotenoids it could be demonstrated that the MSRRS cutaneous measurements are not influenced by Fitzpatrick skin types I–VI. The MSRRS sensor is commercially available under the brand name biozoom.