Put one make three: Multifunctional near-infrared fluorescent probe for simultaneous detection of viscosity, polarity, SO2/H2O2

Polarity and viscosity are critical parameters of the cellular microenvironment, closely linked to diseases such as diabetes and cancer. Hydrogen peroxide (H2O2) and sulfur dioxide (SO2) serve as essential oxidizing and anti-oxidant agents, maintaining a delicate balance vital for normal physiological function. Disruptions in the cellular microenvironment or oxidative balance can trigger various pathological conditions. Therefore, monitoring changes in polarity, viscosity, and the reversible interactions between SO2 and H2O2 is crucial for advancing disease research. In this study, we developed a versatile near-infrared (NIR) fluorescent probe, CCA, with an emission peak at 705 nm, capable of simultaneously detecting viscosity, polarity, and SO2/H2O2 levels. Its fluorescence is governed by intramolecular charge transfer (ICT) and twisted intramolecular charge transfer (TICT) mechanisms, exhibiting strong emission under low-polarity and high-viscosity conditions, enabling the distinction between cancerous and normal cells based on their differing cellular environments. Additionally, the CCA probe offers a reversible response to SO2 and H2O2. The unsaturated C = C bond within CCA reacts with bisulfite (HSO3-), forming a new compound, CCA-SO32-, which quenches fluorescence, and is subsequently reversibly oxidized back to CCA by H2O2, restoring the near-infrared emission at 705 nm. This ability to detect multiple biomarkers simultaneously provides a convenient and versatile method for early cancer diagnosis and therapeutic monitoring. Furthermore, we believe this probe has significant potential for future in vivo applications, including highly sensitive, multi-targeted cancer diagnostics.