A dual-targeted mitochondria and lipid droplets near-infrared probe for visualizing viscosity and sulfur dioxide...

The simultaneous monitoring of viscosity and sulfur dioxide (SO₂) fluctuations within the inflammatory microenvironment offered significant potential for evaluating inflammation-associated pathological conditions. To address this need, the study developed a novel near-infrared fluorescent probe, TTBP, based on a dual-organelle (mitochondria and lipid droplets (LDs)) targeting and dual-biomarkers (viscosity and SO₂) detection strategy. TTBP was designed by integrating a triphenylamine-thiophene unit with a benzopyrylium salt unit. It exhibited a marked viscosity-dependent enhancement of red fluorescence at 740 nm, with fluorescence intensity showing a strong linear correlation with the logarithm of viscosity (R² = 0.9960). Meanwhile, via specific nucleophilic addition at the benzopyrylium C = C bond, TTBP produced a highly sensitive turn-on fluorescence signal at 495 nm in response to SO₂, showing a detection limit of 0.54 µM. In bioimaging applications, TTBP selectively localized to mitochondria driven by its positive charge, adduct, TTBP‑SO₃H, accumulated specifically in LDs, enabling dynamic tracking from mitochondria to LDs. The probe was successfully applied for dual-channel fluorescence imaging of SO₂ in HeLa cells and zebrafish. Furthermore, it sensitively monitored nystatin-induced viscosity increases in cells and zebrafish. These results demonstrated that TTBP showed potential as a molecular tool for investigating inflammation-associated microenvironmental changes, metabolic dysfunction, and related disease mechanisms.