Calcium imaging techniques in cell lines

Calcium imaging is a scientific technique which is designed to measure the intracellular free calcium concentration (Ca2+) in an isolated cell or tissue. Calcium imaging techniques utilizes fluorescent molecules so called Ca2+ indicators that can respond to the binding of Ca2+ ions by changing  heir fluorescence properties. Binding of a Ca2+ ion to a fluorescent indicator molecule leads to either an elevation in its fluorescence intensity or emission/excitation wavelength shift. Two main classes of calcium indicators are chemical indicators and genetically encoded calcium indicators. Chemical indicators are small molecules that can bind calcium ions. This group of indicators includes Fura-2, Fluo-3, Fluo-4, Rhod-2. These dyes are often used with acetoxymethyl esters, in order to render the molecule lipophilic and to allow easy entrance into the cell. Genetically encoded indicators do not need to be loaded onto cells, instead the genes encoding for these proteins can be easily transfected to cells. These indicators are fluorescent proteins derived from green fluorescent protein (GFP). The time-scan mode of laser confocal microscopy is often used for calcium imaging. Intracellular Ca2+ ions generate versatile  intracellular signals that control key functions in all types of cells. In sensory neurons Ca2+ signals are associated with pain transmission.