Excited state kinetics of tryptophan and NAD(P)H in blood plasma of normal and abnormal liver conditions: A tool to understand the metabolic changes and classification

Abstract

Early diagnosis at the metabolomic level is crucial for the treatment of liver cirrhosis and hepatocellular carcinoma (HCC). In this study, attempts were made to investigate the excited-state kinetics of intrinsic fluorophores, tryptophan and nicotinamide adenine dinucleotide (NADH) to understand the metabolic changes associated with the transformation of normal liver into cirrhosis and HCC. Significant variations were observed in the values of average fluorescence lifetimes for 350 nm (τ_{avg_350}) and 450 nm (τ_{avg_450}) emissions for cirrhosis and HCC with respect to normal samples. The classification results of hierarchical cluster analysis (HCA) and receiver operator characteristics (ROC) based on the values of τ_{avg_350} discriminates normal from liver diseased group (cirrhosis and HCC) with 86.95 % sensitivity and 96.43 % specificity. In the case of τ_{avg_450} values, 95.65 % sensitivity is obtained for both HCA and ROC analyses. However, specificity of 100 % and 92.86 % was obtained in ROC and HCA analysis, respectively. The changes in the values of τ_{avg_350}, τ_{avg_450} and NADH_free/NADH_bound in cirrhosis cases after surgery are shifting towards the respective values of normal group. Among the decay kinetics of two emissions, the emission at 450 nm provides better discrimination than 350 nm emission.