Photon-burst analysis in two-photon fluorescence excitation flow cytometry.

We studied the use of a dramatically reduced testing zone in combination with two-photon excitation and photon-burst analysis in high-throughput rare-event detection simulation using a modified flow cytometer. Two-photon excitation measurements were performed with a mode-locked titanium:sapphire laser. Fluorescence emission was measured with a photon-counting avalanche photodiode. Measured signal was analysed offline by autocorrelation and burst detection methods. Test samples were composed of full blood and orange fluorescent polystyrene nanospheres mixed in full blood. Results show that two-photon fluorescence excitation and time-correlation analysis provide a good signal-to-noise ratio for rare-event particle detection in a turbid sample environment.