Small Molecular Fluorescent Probes for Imaging of Viscosity in Living Biosystems.

Viscosity, as a vital microenvironment parameter, is tightly associated with multitudinous cellular processes and diseases. Recently, precise visualization of viscosity has started to arouse more and more interest. However, owing to the complicated character, it is still a huge challenge to directly observe viscosity in living systems. In this regard, mounting fluorescence probes are being increasingly fabricated to map viscosity inside live cells and small animals. In this minireview, the viscosity-sensitive small molecular fluorescent probes used in bioimaging are comprehensively summarized, mainly focusing on the last three years. Moreover, the current challenges and opportunities for the development of viscosity-specific fluorescent probes will be discussed.