Differentiation between normal and cancer cells with autofluorescence lifetime microscopy and nanosecond pulsed electric field effects

Fluorescence lifetime images of the endogenous nicotinamide adenine dinucleotide (NADH), which is well known as autofluorescence chromophores, were obtained for rat normal fibroblast cells (WFB) and H-ras oncogene-transfected WFB cancer cells (W31) and for human normal lung fibroblast (MRC-5) and human lung large carcinoma (HCI-H661). In both cases, the average lifetime of the NADH autofluorescence was shorter in cancer cells than in normal cells, indicating that the difference in metabolism between healthy and cancer cells might alter the level of coenzymes such as NADH. It is also shown that application of nanosecond pulsed electric field (nsPEF) induces apoptosis in these cell, resulting in the morphological changes and lengthening the autofluorescence lifetime of NADH. Furthermore, we found that nsPEF more efficiently affected cancer cells than normal cells in cell viability, suggesting the possibility of drug-free cancer therapy by nsPEF.