A Two‐Photon Ratiometric Fluorescent Probe for Imaging of Hydrogen Peroxide Levels in Rat Organ Tissues

Hydrogen peroxide (H(2)O(2)) is important in the regulation of a variety of biological processes and is involved in various diseases. Quantitative measurement of H(2)O(2) levels at the subcellular level is important for understanding its positive and negative effects on biological processes. Herein, a two‐photon ratiometric fluorescent probe (SHP‐Cyto) with a boronate‐based carbamate leaving group as the H(2)O(2) reactive trigger and 6‐(benzo[d]thiazol‐2′‐yl)‐2‐(N,N‐dimethylamino) naphthalene (BTDAN) as the fluorophore was synthesized and examined for its ability to detect cytosolic H(2)O(2) in situ. This probe, based on the specific reaction between boronate and H(2)O(2), displayed a fluorescent color change (455 to 528 nm) in response to H(2)O(2) in the presence of diverse reactive oxygen species in a physiological medium. In addition, ratiometric two‐photon microscopy (TPM) images with SHP‐Cyto revealed that H(2)O(2) levels gradually increased from brain to kidney, skin, heart, lung, and then liver tissues. SHP‐Cyto was successfully applied to the imaging of endogenously produced cytosolic H(2)O(2) levels in live cells and various rat organs by using TPM.