Ultrasensitive flow cytometric analyses

New techniques and approaches to cellular analysis are being developed at the Los Alamos National Flow Cytometry Resource. These developments can be divided into those that improve sensitivity through the implementation of new measurement techniques and those that move the technology into new areas by refining existing approaches. An example of the first category is a flow cytometric system being assembled that is capable of measuring the phase shift of fluorescence emitted by fluorophors bound to cells. This phase sensitive cytometer is capable of quantifying fluorescence life time on a cell-by-cell basis as well as using the phase sensitive detection to separate fluorescence emissions that overlap spectrally but have different lifetimes. A Fourier transform flow cytometer capable of measuring the fluorescence emission spectrum of individual labeled cells at rates approaching several hundred per second is also in the new technology category. The current implementation is capable of resolving the visible region of the spectrum into 8 bands. With this instrument, it is possible to resolve the contributions of fluorophors with overlapping emission spectra and to determine the emission spectra of dyes such as calcium concentration indicators that are sensitive to the physiological environment.