Fiberoptic Resonance Raman Spectroscopy to Measure Carotenoid Oxidative Breakdown in Live Tissues

Abstract

Based on compelling epidemiologic and corroboratory in vitro studies, carotenoids are thought to have great potential as dietary prevention against cancer. Yet, carotenoid-based chemopreventive trials have found very contradictory results. Definitive conclusions from these trials are hampered by an inability to accurately and safely measure carotenoids in specific tissues at risk of cancer development. Raman spectroscopy has been proposed as an optical technology with which to analyze various molecules in live tissues. One major obstacle that impedes the clinical use of this powerful technology is the lack of a fiberoptic Raman probe suitable for endoscopic tissue evaluation. A single-fiber resonance Raman Spectroscope capable of noninvasive "optical biopsies" to measure carotenoid concentrations in live tissues has been developed. The accuracy of this Raman instrument was confirmed by comparison with more standard methods of spectrophotometry and high-pressure liquid chromatography using solubilized β-carotene (BC) and BC-loaded cells before use in a small patient cohort. This Raman instrument detected intact BC as well as BC oxidative breakdown as a decrement of its Raman signal in cells. Use of the Raman instrument in our small cohort study showed its feasibility for measuring human tissues and raised some potentially intriguing possibilities about BC tissue pharmacokinetics and oxidative biology. Based on these results, our newly developed single fiberoptic resonance Raman instrument may provide a very useful method of measuring carotenoids and their oxidative breakdown within live tissue during future carotenoid chemopreventive trials. This proof-of-concept study provides the foundation to justify future validation of our Raman prototype.

Quantitative determination of low molecular weight antioxidants and their effects on different antioxidants in chicken blood plasma

“…Therefore, increased levels of carotenoids reflect overall levels of antioxidant defense and diminished oxidative stress. In addition, non invasive methods have been developed based on an optical method known as Resonance Raman Spectroscopy [40]. This method has been used for many years in research laboratories for carotenoid investigations in biological systems using optical signals, called raman signals.…”

Optical assessment of skin carotenoid status as a biomarker of vegetable and fruit intake

“…Following proof of concept, the RRS method quickly found exclusive use in the nutritional supplement industry, where to date more than 10,000 portable instruments are in use to monitor the efficacy of carotenoid-containing nutritional supplement formulations (Biophotonic Scanner, NuSkin/Pharmanex, Inc.). After completion of comprehensive validation studies [2,7,8,9, 10] via skin biopsy [2,7] (with correlation coefficients R = 0.66 [2] and R = 0.95 [7], respectively), fasting serum [2,8,9] (R = 0.62, R = 0.78, and R = 0.82, respectively), two-month food frequency V/F questionnaire [2] (R = 0.52), and a controlled feeding study [10], the RRS method is more recently also finding use in nutrition science [10–15] and medical research studies investigating the role of carotenoids in human health [16–23].…”

Dermal carotenoid measurements via pressure mediated reflection spectroscopy

“…Initially we could show that carotenoid levels measured with RRS in the inner palm of the hand correlate strongly and significantly with HPLC-derived carotenoid levels of fasting serum, thus validating the method in an indirect way [16]. RRS is now finding increasing use as rapid objective carotenoid biomarker also in areas such as Nutrition [19,20,21], Cancer Prevention [22] and Neonatology Research [23]. Again, a high correlation was found between both methods.…”