Analytical performance of an ultrasonic particle focusing flow cytometer.

Creation of inexpensive small-flow cytometers is important for applications ranging from disease diagnosis in resource-poor areas to use in distributed sensor networks. In conventional-flow cytometers, hydrodynamics focus particles to the center of a flow stream for analysis, which requires sheath fluid that increases consumable use and waste while dramatically reducing instrument portability. Here we have evaluated, using quantitative measurements of fluorescent microspheres and cells, the performance of a flow cytometer that uses acoustic energy to focus particles to the center of a flow stream. This evaluation demonstrated measurement precision for fluorescence and side scatter CVs for alignment microspheres of 2.54% and 7.7%, respectively. Particles bearing 7 x 10(3) fluorophores were well resolved in a background of 50 nM free fluorophore. The lower limit of detection was determined to be about 650 fluorescein molecules. Analysis of Chinese hamster cells on the system demonstrated that acoustic focusing had no effect on cellular viability. These results indicate that the ultrasonic flow cytometer has the necessary performance for most flow cytometry applications. Furthermore, through robust engineering approaches and the combination of acoustic focusing with low-cost light sources, detectors, and data acquisition systems, it will be possible to achieve a low-cost, truly portable flow cytometer.