Fluorescence Microscopy/Imaging Flow Cytometry Organic Dyes Quantum Dots Fluorogens
The core of a flow cytometer is where the liquid flow intersects a laser beam. The light from the laser interrogates the particles in the stream (ie beads or cells) and will either be scattered from the particle flow or will elicit fluorescence if the particles contain a chromophore that is excitable by the laser used. Both the scattered laser light and fluorescence emission are collected and directed to a detection assembly via a set of steering optics. The user can then subsequently define criteria that enables the instrument to extract a particular particle population (either using scattered light or a particular fluorescence emission color as a basis) and sort them into an appropriate receptacle. Any particles that are not sorted out of the stream continue down to liquid waste.
Another instrument that is used to measure and sort samples based on gross fluorescence is a fluorescence plate reader. This particular technology can make rapid fluorescence measurements of many samples contained within multi-well plate. This enables users to screen many samples at once for gross fluorescence. It is possible however, for example, that some cells in a given well may be fluorescent and others not and this particular methodology does not enable the user to identify those potential sub-populations. In comparison, flow cytometry allows the user to measure each cell individually and thus gate out dead or senescent cells and even undesirable background fluorescence from culture media, and as such acts as the perfect complimentary measurement technology to fluorescence plate readers.
