Quantitative Raman Analysis of Human blood serum of glaucoma patients supplemented with macular pigment carotenoids.

Carotenoids have been widely studied for their high dietary, antioxidant, and vision protection roles in the human body. Blood contains all major dietary carotenoids and hence presents as a suitable and efficient substrate for the estimation of dietary carotenoids in vivo. Following the 18-month supplementation of open angle glaucoma patients with macula pigment carotenoids (Lutein, Zeaxanthin and Meso-Zeaxanthin) in the European Nutrition in Glaucoma Management (ENIGMA) trial, Raman spectroscopic analysis of the pre-supplementation baseline and 18-month supplemented blood serum carotenoids from participants was carried out, to investigate the systemic impact of supplementation in the blood and explore a more direct way of quantifying this impact using a routine blood test. A 532 nm laser source was used to provide optimal response. After pre-processing techniques were carried out to remove water and glass contributions, principal components analysis (PCA) was used to differentially analyse serum spectra, of the pre and post-supplementation data sets, a data set of matched pre- and post-supplementation patient samples, and in patients with the highest and lowest carotenoid signals. Following supplementation, a consistent increase in serum carotenoid concentration was observed from the corrected spectra and PC1 loadings, indicating an increase due to the carotenoid supplementation regimen. PCA also revealed differences in the structural profile of the carotenoid content of the two groups, indicated by a shift in the 1519 cm-1 carotenoid peak, consistent with an increased content of the supplemented carotenoids in the blood stream. This increase was also seen to be highest in patients which had a high baseline carotenoid content. The findings highlight the potential of Raman spectroscopy to quantify and differentiate carotenoids directly in blood serum. It could provide guidance for individualised supplementation regime for the management of diseases for which the dietary carotenoids are directly implicated.