Detection of cell metabolism via wavelength- and time-resolved intracellular autofluorescence

Abstract

A time-resolved confocal fluorescence spectroscopy system was instrumented utilizing the multi-channel time-correlated single photon counting (TCSPC) technique. The system provided a unique approach to investigate the relationship between wavelength- and time-resolved cell autofluorescence and cellular metabolic status. The experiments were carried out on monolayered cell cultures including normal and cancer ectocervical cells. With UV excitation at 365 nm, the decay of cellular fluorescence can be well described by a dual-exponential function, consisting of a short lifetime component ((tau) 1 ~ 0.40 - 0.47 ns) and a long lifetime component (((tau) 2 ~ 3.3 - 4.0 ns). By analyzing the decay-associated spectra of the short and long lifetime components, we found that the long lifetime component carried the information of protein-bound NADH and short lifetime component was mainly determined by free NADH with certain interference from bound NADH. Moreover, it was found that the ratio of the amplitudes of two lifetime components, dominated by free/bound NADH, was sensitive to cell metabolism. Overall, this study demonstrated that wavelength- and timeresolved autofluorescence can be potentially used as an important contrast mechanism to detect epithelial pre-cancer.