Non-invasive Raman spectroscopic detection of carotenoids in human skin

Carotenoids are thought to play a significant part in the skin's anti-oxida nt defense system, and may help prevent malignancy. Inability to measure sk in carotenoid content readily has, however, made it difficult to establish the relationship between carotenoid concentration and the occurrence of cut aneous malignancy. We have measured in vivo carotenoid concentration using a noninvasive optical method, Raman spectroscopy. To validate our instrumen tation, abdominoplasty skin was evaluated by both Raman spectroscopy and hi gh-performance liquid chromatography determination for carotenoid content. Evaluation of the Raman signal in specific carotenoid solutions was also pe rformed. Precision of Raman measurements within skin sites, within subjects , and between subjects was measured. Sensitivity of the method was evaluate d as a function of anatomical region and the distribution of carotenoids wi thin the stratum corneum, Lastly, we evaluated the Raman signal in actinic keratosis and basal cell carcinoma lesions and perilesional skin and compar ed this with region-matched sites in healthy subjects. Our results indicate that the Raman scattering method reflects the presence of carotenoids in h uman skin and is highly reproducible. Evaluation of five anatomical regions demonstrated significant differences in carotenoid concentration by body r egion with the highest carotenoid concentration noted in the palm. Comparis on of carotenoid concentrations in basal cell carcinomas, actinic keratosis , and their perilesional skin demonstrate a significantly lower carotenoid concentration than in region-matched skin of healthy subjects. These result s represent the first evidence that carotenoid concentration in the skin co rrelate with the presence or absence of skin cancer and precancerous lesion s.