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The state of internal human homeostasis, namely the function of the internal organs - the endocrine system, the digestive tract, the nervous, hematopoietic, cardiovascular and other systems, is closely related to the skin condition. Changes in the skin biochemistry are a reflection of the internal state of the human body. Therefore, the analysis of changes in the composition of human skin various layers is one of complex parts of therapeutic disciplines. In addition to the laboratory analysis methods used today, a variety of physical methods can be successfully used to study the component composition of the human skin. Methods of Raman Spectroscopy and autofluorescence analysis can detect changes in the component composition of the skin at the molecular level. In current study we used Raman spectroscopy and autofluorescence analysis in visible and NIR regions for the analysis of human skin spectral characteristics in the presence of various influencing factors including chronic kidney transplant dysfunction.
The Raman and autofluorescence spectral characteristics of studied samples in NIR region were registered using the experimental setup, incorporated a high-resolution spectrometer with integrated cooled digital camera, a fiber-optic Raman probe and the laser module with central wavelength 785 nm. The autofluorescence human skin response in visible region was registered by portable diagnostic fluorimeter, which provide an excitation light source across the 350-400 nm range and measured light intensity within the 420-600 nm range. In this study we describe the design and results of the tests on volunteers of portable fluorescence meter based on two photodiodes. One channel of such fluorometer is used for measurement of autofluorescence intensity, another one - for intensity of elastically scattered radiation, which can be used as reference. The processing of experimental data was performed on the basis of regression analysis.
We performed the comparative research of Raman experimental data and visible autofluorescence analysis results. We estimated correlations between Raman and autofluorescence signals and also find informative Raman bands that may be used as predictors of general condition of the body. These bands lie in 1170 – 1700 cm-1 region. We demonstrated the possibility to measure melanin and lipofuscin levels in the skin, as they are the hallmarks of skin aging; and demonstrated the possibility to measure a level of advanced glycation end products in the skin, advanced glycation end products as and lipofuscins are markers of general body condition. In addition, we have found informative spectral bands characterizing changes in the component composition of the skin in the presence of various influencing factors as kidney diseases.
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