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.

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 (τavg_350) and 450 nm (τavg_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 τavg_350 discriminates normal from liver diseased group (cirrhosis and HCC) with 86.95 % sensitivity and 96.43 % specificity. In the case of τavg_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 τavg_350, τavg_450 and NADHfree/NADHbound 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.