LDs-targeting multifunctional fluorescent probe toward polarity, viscosity, and SO2 and bioimaging in cancer, inflammation, ferroptosis, and acute alcoholic liver injury

Sulfur dioxide (SO₂), as well as microenvironmental viscosity and polarity are indispensable for redox equilibrium, biomolecular trafficking, and metabolic signaling, yet holistic analysis tools are lacking. Herein, we developed a multifunctional fluorescent probe TPA-TOB for simultaneous detection of polarity, viscosity, and SO₂. In the D-π-A structured TPA-TOB , triphenylamine (TPA) functioned as the donor, with 2-thiobarbituric acid serving as the acceptor, linked by a thiophene vinyl π-bridge. This architecture targeted lipid droplets (LDs), while the C C bond served as the site of the Michael addition reaction for the recognition of SO 2 . The D-π-A structure of TPA-TOB with twisted intramolecular charge transfer (TICT) characteristics enabled it to respond to polarity and viscosity (≥620 nm fluorescence enhancement with higher viscosity/lower polarity). For SO₂, TPA-TOB exhibited 47-fold fluorescence enhancement at 420 nm (response time ~ 10 min, LOD 0.87 μM), with 95.78%–100.58% recovery for SO₂ detection in rock sugar. Furthermore, TPA-TOB facilitated dynamic monitoring of intracellular SO 2 redox dynamics and fluctuation of LDs microenvironment (polarity and viscosity) spanning cell, tissue, and organism levels. Significantly, we realized the dual-channel mapping of acute alcoholic liver injury (AALI) with this probe, as well as identification of pathological signatures in cancer, inflammation, and ferroptosis. Therefore, we have established an integrative analytical platform to elucidate the interplay between SO 2 signaling and LDs microenvironment, thereby deepening the understanding of their roles in the pathogenesis of multiple diseases, and providing novel avenues for mechanistic investigation and therapeutic discovery.