Fluorescence Correlation Spectroscopy
Fluorescence correlation spectroscopy (FCS) is an experimental technique allowing studies of the diffusion properties of fluorescent tracers in various environments with very high sensitivity, down to a single molecule level. The method is based on detecting the fluctuations of the fluorescent light intensity caused by the diffusion of tracers through a small (< fL) observation volume. A correlation analysis of these fluctuations provides information on the diffusion rate of the tracers and therefore on their size and the properties of the environment. Tracers can be single fluorescent molecules or macromolecules, quantum dots, fluorescent nanoparticles, etc. In our FCS Lab, commercial and home-build setups are combined in order to achieve unique features. These include the possibility to study flows near solid surfaces with total internal reflection fluorescence cross-correlation spectroscopy (TIR-FCCS), to characterize polymer matrices by simultaneously measuring the diffusion coefficient and the fluorescent live time of molecular rotors or to monitor drug nanocarriers in flowing blood with near infrared FCS.