Construction of a novel bifunctional fluorescent probe for monitoring changes in intracellular viscosity and meat freshness.

Biogenic amines (BAs), which are mainly produced during meat decomposition, are a health hazard when ingested in excess and may lead to various diseases. Viscosity is an important parameter of the cellular microenvironment and many diseases cause abnormalities in intracellular viscosity. Although many fluorescent probes have been developed for the detection of intracellular viscosity or BAs, there are still few probes that can detect both viscosity and BAs. Based on this, there is an urgent need for a fluorescent probe that can simultaneously detect viscosity and BAs. We have innovatively synthesized a quinolinium salt derivative-based probe, QF-G, which exhibits distinct dual-channel responses: under high viscosity conditions, QF-G displays a visible color deepening and emits bright red fluorescence at 640 nm; conversely, in the presence of BAs, QF-G shows significant color fading and emits bright blue fluorescence at 475 nm. Notably, owing to its low cytotoxicity and effective mitochondrial targeting, QF-G has been successfully applied to monitor viscosity changes within MCF-7 and 4T1 cells. Furthermore, integrating QF-G into a sensing hydrogel allows for monitoring meat freshness changes across different species via both colorimetric and fluorescent methods. These clear visual and fluorescent signal changes demonstrate that QF-G can detect both analytes by visual observation and fluorescence. Furthermore, low cytotoxicity and abundant materialization applications show significant potential for applications in both human health monitoring and food safety assessment.