Fluctuation correlation spectroscopy and its applications in homogeneous analysis

Fluctuation correlation spectroscopy (FCS) is a single-molecule/particle detection technique based on measuring signal fluctuations in a highly focused detection volume. Multiple-parameter information can be obtained from the FCS measurement including the amplitude, characteristic diffusion time of correlation curve, and brightness of the adopted probes. The multiple-parameter change is related with physical or chemical change occurring in the probes. Meanwhile, the detection method has advantages such as short sample time in seconds, sample volume with low limit in femtoliters, and mixing to detection without any separations. These advantages make the FCS technique suitable for homogeneous analysis. In this review, we summarized recent novel applications of FCS and its variants in homogeneous analysis including nucleic acid analysis, protein analysis, enzyme activity assay, direct characterization of nanoparticles in solution, and others. Graphical abstract