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

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.