Functional Phenotype Flow Cytometry: On Chip Sorting of Individual Cells According to Responses to Stimuli

The ability to effectively separate and isolate biological cells into specific and well-defined subpopulations is crucial for the advancement of our understanding of cellular heterogeneity and its relevance to living systems. Here is described the development of the functional phenotype flow cytometer (FPFC), a new device designed to separate cells on the basis of their in situ real-time phenotypic responses to stimuli. The FPFC performs a cascade of cell processing steps on a microfluidic platform: introduces biological cells one at a time into a solution of a biological reagent that acts as a stimulus, incubates the cells with the stimulus solution in a flow, and sorts the cells into subpopulations according to their phenotypic responses to the provided stimulus. The presented implementation of the FPFC uses intracellular fluorescence as a readout, incubates cells for 75 s, and operates at a throughput of up to 4 cells min^-1 -resulting in the profiling and sorting of hundreds of cells within a few hours. The design and operation of the FPFC are validated by sorting cells from the human Burkitt's lymphoma cancerous cell line Ramos on the basis of their response to activation of the B cell antigen receptor (BCR) by a targeted monoclonal antibody.