Resonance Raman detection of carotenoid antioxidants in living human tissue

Abstract

Increasing evidence points to the beneficial effects of carotenoid antioxidants in the human body. Several studies, for example, support the protective role of lutein and zeaxanthin in the prevention of age-related eye diseases. If present in high concentrations in the macular region of the retina, lutein and zeaxanthin provide pigmentation in this most light sensitive retinal spot, and as a result of light filtering and/or antioxidant action, delay the onset of macular degeneration with increasing age. Other carotenoids, such as lycopene and beta-carotene, play an important role as well in the protection of skin from UV and short-wavelength visible radiation. Lutein and lycopene may also have protective function for cardiovascular health, and lycopene may play a role in the prevention of prostate cancer. Motivated by the growing importance of carotenoids in health and disease, and recognizing the lack of any accepted noninvasive technology for the detection of carotenoids in living human tissue, we explore resonance Raman spectroscopy as a novel approach for noninvasive, laser optical carotenoid detection. We review the main results achieved recently with the Raman detection approach. Initially we applied the method to the detection of macular carotenoid pigments, and more recently to the detection of carotenoids in human skin and mucosal tissues. Using skin carotenoid Raman instruments, we measure the carotenoid response from the stratum corneum layer of the palm of the hand for a population of 1375 subjects and develope a portable skin Raman scanner for field studies. These experiments reveal that carotenoids are a good indicator of antioxidant status. They show that people with high oxidative stress, like smokers, and subjects with high sunlight exposure, in general, have reduced skin carotenoid levels, independent of their dietary carotenoid consumption. We find the Raman technique to be precise, specific, sensitive, and well suitable for clinical as well as field studies. The noninvasive laser technique may become a useful method for the correlation between tissue carotenoid levels and risk for malignancies or other degenerative diseases associated with oxidative stress.

Resonance Raman imaging of macular pigment distributions in the human retina

“…2. Under laser excitation with spectral overlap of the MP absorption, a resonance Raman response is obtained only from the MP-containing retinal layer [24]. Fluorescence signals of MP can be neglected since the corresponding fluorescence quantum efficiency is extremely weak.…”

“…Resonance Raman spectroscopy has been previously used as an objective optical approach for the detection of carotenoids in living human tissue, including the skin and the retina [24][25][26]. This Raman method uses excitation of the carotenoids in their absorption band occurring in the blue/green wavelength region and detects resonantly enhanced light scattered at a frequency that is downshifted from the laser excitation frequency by the amount of the vibrational stretch frequency of the carbon double bonds (1525 cm −1 ) that are part of the backbone of all carotenoid molecules.…”

Nonmydriatic fluorescence-based quantitative imaging of human macular pigment distributions

“…11,26 This method detects the light that is Raman scattered from the MP carotenoid molecules at their 1525 cm −1 C=C double bond stretch frequency under resonant excitation in the MP absorption band. The Raman method measures the response of MP directly, has a very high molecule specificity, and has been validated by correlating Ramanimage-derived MP distributions with HPLC-derived MP levels in excised human eye cups and living monkey eyes.…”

Dynamic molecular monitoring of retina inflammation byin vivoRaman spectroscopy coupled with multivariate analysis

“…Several recent studies have applied this technology to retinal tissue both in animal models and in human subjects in vivo to quantify macular carotenoid pigments [7], advanced glycosilation end products (AGE) levels in Brusch membranes [8], and to differentiate between the molecular content of different retinal layers [9]. Another Raman related technology is coherent antiStokes Raman spectroscopy (CARS), which has been applied for obtaining in vivo microscopy images without staining, such as the elucidation of myelin damage in spinal cords following glutamate excitotoxicity in guinea pigs [10].…”