Use of lipophilic fluorescent probes for the isolation of hybrid cells in flow cytometry.

Flow cytometry was used for the isolation of hybrid cells immediately after fusion. Precursor cells were stained by two lipophilic fluorescent probes: perylenoyl-labeled triglyceride (perylenoyl-TG, green fluorescence, 520 nm) and rhomdaminyl-labeled triglyceride (rhodaminyl-TG, red fluorescence, greater than 580 nm). Since the maximum emission of perylenoyl-TG coincides with the maximum absorbance of rhodaminyl-TG, the two fluorescent dyes form an effective donor-acceptor pair. Cells stained by perylenoyl-TG (0.25-1 microgram/ml) at the excitation wavelength of 457 nm displayed high intensity of fluorescence in the green region (520 nm), and low intensity of fluorescence in the red region (greater than 580 nm). Using the same conditions, cells that were stained by rhodaminyl-TG displayed a low intensity of fluorescence in both regions. When cells were simultaneously labeled by perylenoyl-TG and rhodaminyl-TG (used in a concentration ratio of 1:10, respectively) essentially total energy transfer was observed, and the cells exhibited a high intensity of red fluorescence. After the fusion of cells which had been separated stained by perylenoyl-TG and rhodaminyl-TG, the hybrid cells containing the two fluorescent probes had a high intensity of red fluorescence. Resonance exitation energy transfer between the two fluorescent dyes permits effective sorting of hybrid cells by flow cytofluorometry.