Polychromatic Flow Cytometry With An Avalanche Photodiode Array

Multi parameter flow cytometry enables detailed identification of cell type and function based on fluorescence of antibody conjugated dye labels. Current instruments use photomultiplier tube detectors to measure up to eight fluorescent labels from a single excitation source. We demonstrate polychromatic flow cytometry using a 14-element avalanche photodiode (APD) array coupled with a dispersive optical grating. Forward scatter, side scatter, and 14 fluorescence channels over the 530 to 800 nm spectral range are recorded using a 16 channel electronics console for simultaneous event capture. The APD detector elements have a working spectral range from 400 nm to 1050 nm. Results are presented for flow cytometry measurements of Spherotech UltraRainbow test beads, quantum dot labeled polystyrene spheres, and cells with antibody conjugated dye labels. The flow cytometry test bead measurements illustrate the sensitivity and spectral resolution of the APD detector array. The application of the instrument is demonstrated by identifying CD4 positive lymphocyte populations in normal human whole blood samples.