A portable fluorescence meter with two photodetector channels was developed for risk assessment of cardiovascular diseases by in vivo measurement of advanced glycation end products (AGEs) content in the skin. One of the channels served to measure the intensity of the skin autofluorescence, and the other channel was used for normalization to the patient’s skin phototype by measuring the intensity of diffuse scattered radiation. A light-emitting diode with the peak wavelength 365 nm was used for excitation and silicon photodiodes with band filters served as photodetector assay. The AGEs measurements was performed for 70 patients with coronary heart disease and 100 practically healthy volunteers. The age grouping of patients have been used to reveal the trends in the variation of autofluorescence intensity with the factors of natural age degradation of skin collagen. It was shown that the pathologic process related to the metabolic stress directly determines the skin autofluorescence in patients with coronary heart disease.
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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