A red-emitting fluorescent probe with large stokes shift for monitoring of viscosity and polarity and its application in bioimaging, distinguishing cancer cells

Viscosity plays a pivotal role as one of the most critical microenvironments within cellular systems. Aberrant fluctuations in intracellular viscosity have been established as a significant biomarker for various pathological conditions. The application of fluorescent probe technology to monitor viscosity changes in the cellular microenvironment holds substantial importance for advancing our understanding of cellular functions, elucidating strain mechanisms, and developing therapeutic strategies for diseases. In this study, we developed a novel red-emitting fluorescent probe featuring a large Stokes shift. This probe demonstrates exceptional sensitivity to both elevated viscosity and reduced polarity, endowing it with specific targeting capabilities towards lipid droplets. Through cellular imaging applications, the probe effectively detected oleic acid-induced and drug-mediated alterations in intracellular viscosity and polarity. Moreover, it exhibited remarkable potential in discriminating between cancerous and normal cells, as well as distinguishing cells with differential proliferation rates within the same cancer cell line. The probe's efficacy was further corroborated through zebrafish imaging experiments, which confirmed its ability to monitor viscosity changes in living organisms. This probe enables real-time observation of dynamic viscosity changes within cells, which holds significant implications for understanding biochemical reactions, molecular transport, and disease states within cells.