A highly sensitive ESIPT-TICT fluorescent probe for viscosity detection in liver injury models

Cellular viscosity is a critical parameter that regulates essential biological functions, and its dysregulation has been associated with diseases such as liver injury, underscoring the necessity for effective monitoring tools. While conventional viscometers are not suitable for biological systems, fluorescence probes provide real-time, in-situ detection capabilities. In this study, we designed and synthesized a novel benzothiazole-based viscosity-sensitive fluorescent probe (VFP) that operated on a combined mechanism of excited-state intramolecular proton transfer (ESIPT) and twisted intramolecular charge transfer (TICT). The VFP demonstrated an exceptionally large Stokes shift of 260 nm, along with high sensitivity and excellent selectivity toward changes in viscosity. It successfully monitored variations in cellular viscosity and detected abnormal viscosity levels in liver-injured tissues. Thus, VFP showed potential as a valuable tool for investigating the role of viscosity in disease mechanisms, particularly in the context of liver injury.