Identification of biomarkers on kidney failure by Raman spectroscopy

Chronic kidney disease (CKD) is a global health problem. Our study employed Raman spectroscopy for the first time to analyze potential biomarker such as tryptophan (Trp) on kidney failure and show the difference between normal and CKD groups. Adenine model of CKD characterized most of the physiological changes observed in human CKD. For that, 6-week-old Wistar male rats were assigned to the two groups: the control group, 0.5% carboxymethyl cellulose (CMC) was administered; the CKD group, adenine was administered to rats at a dose 600 mg/kg for 10 days. The Raman spectra were obtained in the spectral range of 100-2500 cm(-1). The excitation source was 532 nm, the laser power was similar to 40 mW, and the analyzed tissue area was 10.02 x 82.12 mu m(2). The results showed a significant reduction in the case of Raman peak intensities at 748, 1359, 1554, and 1636 cm(-1), which can be assigned as Trp. Moreover, it was shown that tyrosine at 1169 cm(-1) and phenylalanine at 1001 cm(-1) decreased in the CKD group. Trp and kynurenine (Kyn) levels in kidney tissue and plasma were analyzed by using the high-performance liquid chromatography (HPLC). The Trp concentrations in plasma and kidney tissue significantly decreased in CKD 7.4 mu g/ml and 0.1 mu g/mg, respectively. However, Kyn level was not a statistically significant change in kidney tissue. In this work, we showed that Raman spectroscopy usage in CKD model and Raman spectroscopy can be considered a promising technique for semi-quantitative analysis of potential biomarkers such as phenylalanine, tyrosine, and Trp of renal function because of the little or no need for sample preparation, and it is easily observing several biomarkers at the same time. The utilization of multivariate analysis method, such as partial least square analysis can be considered as a promising tool for the discrimination of control and CKD groups.

Automated summary

Chronic kidney disease (CKD) is a global health problem, and our study used Raman spectroscopy to analyze potential biomarkers, showing differences between CKD and normal groups, and validating the adenine model of CKD. The results demonstrated a significant reduction of Trp in the CKD group, serving as a potential biomarker for renal function.