Heat Stroke in Cell Tissues Related to Sulfur Dioxide Level Is Precisely Monitored by Light-Controlled Fluorescent Probes

Abstract

Heat stroke (HS) can cause serious organism damage or even death. Early understanding of the mechanism of heat cytotoxicity can prevent or treat heat stroke related diseases. In this work, probe <b>Ly-NT-SP</b> was synthesized, characterized, and used for sulfur dioxide (SO₂) detection in lysosomes. PBS solutions of probe <b>Ly-NT-SP</b> at pH 5.0 present a marked broad emission band in the green zone (535 nm). After UV irradiation, the spiropyran group in <b>Ly-NT-SP</b> isomerizes to the merocyanine form (<b>Ly-NT-MR</b>), which presented a weak red-shifted emission at 630 nm. In addition, photocontrolled isomerization of <b>Ly-NT-SP</b> to <b>Ly-NT-MR</b> generated a C═C-C═N⁺ fragment able to react, through a Michael addition, with SO₂ to yield a highly emissive adduct with a marked fluorescence in the green channel (535 nm). In vitro studies showed a remarkable selectivity of photoactivated <b>Ly-NT-MR</b> to SO₂ with a limit of detection as low as 4.7 μM. MTT viability assays demonstrated that the <b>Ly-NT-SP</b> is nontoxic to HeLa cells and can be used to detect SO₂ in lysosomes. Taking advantage of this, the sensor is successfully applied to image increasing SO₂ values in lysosomes during heat shock for the first time. Moreover, we also confirmed that the increased SO₂ can protect the small intestine against damage induced by heat shock through regulating oxidative stress in cells and mice.