Abstract

Focused beams of light from ion and dye lasers are now routinely used to measure properties and components of cells and cell organelles (e.g., chromosomes). Properties such as size and surface area are measured through the amount of light scattered at various angles as the cells pass through the beam. Through careful selection of fluorescent dyes that excite at different wavelengths, it is possible to measure components of cells, such as DNA, RNA, and protein. Monoclonal antibodies are being developed which are specific to certain chemicals and can be fluorescently tagged. Using more than one laser and combinations of probes, identification of specific ceil types is possible. All these measurements (as many as five in some instruments) are made at high rates (up to several thousand per second) and with great precision (1% coefficient of variation is possible). In some instruments it is possible to remove physically from a cell suspension a selected subpopulation of cells based on measured properties. This device is called a cell sorter and can operate at rates up to 20,000/sec. This paper describes the physical principles involved in making the measurements and several instruments currently in use in biomedical research.

© 1985 Optical Society of America