Open flow cytometer with the combination of 3D hydrodynamic single cell focusing and confocal laser-induced fluorescence detection.

Flow cytometry is among the most powerful tools for single-cell analysis, while the high cost and mechanical complexity of the commercial instrumentation limit the applications in personalized single-cell analysis. For this issue, we hereby construct an open and low-cost flow cytometer. It is highly compact to integrate the functions of (1) single cell aligning by a lab-made modularized 3D hydrodynamic focusing device, and (2) fluorescence detection of the single cells by a confocal laser-induced fluorescence (LIF) detector. The ceiling cost of the entire hardware for the LIF detection unit and 3D focusing device is $ 3200 and $ 400 respectively. A sheath flow velocity of 150 μL/min produces a focused sample stream of 17.6 μm × 14.6 μm at sample flow of 2 μL/min, based on the LIF response frequency and the laser beam spot diameter. The assay performance of the flow cytometer was evaluated by characterizing fluorescent microparticles and acridine orange (AO) stained HepG2 cells, producing throughputs of 40.5/s and 6.2/s respectively. Favorable assay precision and accuracy were demonstrated by the agreement of frequency histogram with imaging analysis, and good Gaussian-like distributions of fluorescent microparticles and AO-stained HepG2 cells. Practically, the flow cytometer was successfully applied for the evaluation of ROS generation in single HepG2 cells.