A novel indolium-fused acridine-based bifunctional fluorescent probe for intracellular viscosity and sulfur dioxide applicate in environmental detection, bioimaging and real-time gas absorption monitoring

Sulfur dioxide (SO₂) is widely recognized as an atmospheric pollutant that is emitted by a variety of industrial processes. Meanwhile, SO₂ is also present in soil, food, water and air, potentially threatening to human health and ecology. Viscosity, a critical parameter for characterizing fluid dynamics, also serves as an essential indicator of cellular changes. Herein, an indolium-fused acridine-based bifunctional fluorescent probe TABP-TI was constructed from nopinone, which can detect SO₂ and viscosity separately by CC, and can be combined with hydrogel technology to achieve real-time detection of SO₂-air. Moreover, TABP-TI exhibited high sensitivity, low detection limit (50 nM for SO₂–detection while 1.18 cp for viscosity–detection), robust anti-interference capabilities, excellent hydrophilicity and optimal pH range (can detect SO₂ and viscosity within the pH range of 2 −9). Additionally, TABP-TI was utilized to detect SO₂ in water, food and soil as well as image viscosity changes in living HepG-2 cells and zebrafish.