Fountain flow cytometry.

Fountain Flow Cytometry (FFC) is a simple and inexpensive technology that is adaptable to situations requiring detection and enumeration of cells/organisms at low concentrations, but is limited to particles of relatively high fluorescence intensity. This work presents the basic physics behind the novel scheme Fountain Flow Cytometry employs for the detection of target particles, a hybrid of conventional flow cytometry and video epifluorescence microscopy. The method is based on LED-induced fluorescence of labeled particles and requires no filtration step. Unlike conventional flow cytometry, the resulting fluorescence is measured with a digital camera as the measured sample flows toward the camera along the optical axis. An automated target particle recognition and enumeration computer program, Biocount, is used to count particles. FFC allows for detection of target particles in transparent and translucent fluids, such as environmental water, blood, and beverages. In addition, FFC can be used for detection of target particles in the presence of high photometric background, including unbound fluorescent dye. This facilitates use of the technique in situations where cells are unwashed. Current applications extend, but are not limited to, particles from µm-size bacteria to multi-millimeter-sized multicellular organisms.