A versatile viscosity-responsive aggregation-induced emission fluorescent probe for bioimaging, fingerprint visualization and food quality monitoring.

Microenvironmental viscosity constitutes a critical physical parameter that modulates biological behaviors, material performances and chemical reaction processes. Accordingly, developing fluorescent probes capable of sensitive and visual detection of microenvironmental viscosity is of great significance. This study designed and synthesized a novel viscosity-responsive fluorescent probe (TPA-Q) based on triphenylamine and hydroxyethyl quinolinium iodide. The probe exhibits weak fluorescence in low-viscosity solvents, but in high-viscosity environments or aggregated states, its intramolecular motion is restricted, leading to significant fluorescence enhancement and thus demonstrating excellent aggregation-induced emission (AIE) properties and viscosity sensitivity. Utilizing this unique characteristic, we successfully utilized this single probe for multi-scenario applications. For food science field, TPA-Q could evaluate the thickening effects of various thickening agents and distinguish the viscosity differences of the actual samples. Moreover, the probe can be used for fingerprint imaging through the method of solution immersion with low concentration. Furthermore, bioimaging experiments verified that TPA-Q could target mitochondria and monitor the viscosity fluctuations under various stimuli. As an AIE probe, TPA-Q displays strong flexibility and practical value of for bioimaging, fingerprint visualization and food quality monitoring.