Time-resolved fluorescence-decay measurement and analysis on single cells by flow cytometry.

A novel method is described for the measurement and analysis of fluorescence decays of individual cells and particles in flow. It combines the rapid measurement capabilities of a flow cytometer and the robust measurement and analysis procedures of time-domain fluorescence-lifetime spectroscopy. For excitation we use a cw laser that is pulse modulated by an electro-optic modulator. The characteristics and the repetition rate of the excitation pulses can be easily adjusted to accommodate fluorescence decays with a wide range of lifetimes.