Measuring macromolecular crowding in cells through fluorescence anisotropy imaging with an AIE fluorogen.

We report a new strategy that allows spatiotemporal visualization of the macromolecular crowding effect in cells. An amine-reactive aggregation-induced emission fluorogen is used to label proteins in the cytoplasm and the change in the protein mobility as well as local viscosity can be monitored by using fluorescence anisotropy imaging and fluorescence lifetime imaging, respectively.