Flow cytometry

Flow cytometry is a photonic technique to study the structure and morphology of populations of micro-particles and cells. It is found in numerous labs ranging from medical to industrial. In cell biology, a flow cytometer can be used to count and sort cells, study the cell structure and morphology, detect cancerous cells, detect biomarkers, aid in protein engineering, and more. Cytometry’s growth and proliferation are attested by thousands of scientific publications and frequent meetings and symposia on the subject, particularly in immunology.

Flow cytometry illustration

A flow cytometer is a quintessential photonic device. It entails these essential components: fluidics, illumination optics, detection optics, photodetectors, electronics, and data analysis and display. A population of cells is introduced into a liquid solution; some or all cells can be tagged with fluorescent dyes. The solution is then injected into a sheath fluid flowing in a capillary. The hydrodynamic focusing forces the cells into a single-file formation along the central axis of the capillary. The cells, one at a time, pass through an interrogation region in the capillary defined by a focused illumination laser light. A passing cell scatters the light. The pattern of the scattered light depends on the size, structure, and morphology of the cell. In addition, the cell, if tagged, will emit fluorescent light. The light detection optics in the forward and side directions sample the scattered light, separate it into specific colors, and direct it to the photodetectors. The detected color, intensity, and duration of the light pulses are recorded and analyzed. The ubiquitous scatter plot of events, relating one measured quantity versus another, is the most common information product from the flow cytometer.

There is ongoing research in extending the capabilities of a flow cytometer to cell imaging and spectroscopy. Hamamatsu is actively involved in this endeavor by partnering with the major manufacturers of flow cytometers and providing expert opinion and technical support on photodetectors.

Application note:

Photodetectors in flow cytometers

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