Fluorescence lifetime imaging (FLIM): Basic concepts and some recent developments

Fluorescence lifetime imaging (FLIM) is a key fluorescence microscopy technique to map the environment and interaction of fluorescent probes. It can report on photophysical events that are difficult or impossible to observe by fluorescence intensity imaging, because FLIM is independent of the local fluorophore concentration and excitation intensity. One prominent FLIM application relevant for biological concerns is the identification of FRET to study protein interactions and conformational changes, but FLIM is also used to image viscosity, temperature, pH, refractive index and ion and oxygen concentrations, all at the cellular level, as well as cell and tissue autofluorescence. The basic principles and recent advances in the application of FLIM, FLIM instrumentation, data analysis, molecular probe and FLIM detector development will be discussed.