Recent advances in multifunctional fluorescent probes for viscosity and analytes

Viscosity has become increasingly important in biological systems, especially as a major factor in the process of diffusion control. The abnormality of viscosity is closely related to the development of many diseases in the cellular microenvironment. The abnormal viscosity behavior of cells is always accompanied with dramatic changes in the levels of relevant active analytes. Therefore, real-time monitoring of local microviscosity and analytes changes in living cells is of great importance. In comparison to conventional imaging approaches, fluorescence imaging has become a powerful tool to detect microenvironments and analytes in living systems as a result of its excellent sensitivity, non-invasive detection, high selectivity and real-time imaging. For the first time, in this review, we focused on the design strategies, spectral performance, and biological applications of multifunctional probes for the simultaneous detection of viscosity and analytes which were reported in recent years. We categorized and discussed the limitations of the present multifunctional probes, proposed new ideas to overcome and change these limitations. We hope this review will provide new research directions for the development of multifunctional probes, which will contribute to the early diagnosis and treatment of diseases, the development and delivery of new drugs.