Synthesis and properties of fluorescent probes in the near-infrared region II of hydrogen peroxide

Hydrogen peroxide (H₂O₂) is an important component of reactive oxygen radicals (ROS), and excessive hydrogen peroxide triggers oxidative stress, leading to apoptosis and tissue damage; therefore, it is important to achieve efficient detection of H₂O₂. Near-infrared II region fluorescent probes have the advantages of deeper tissue penetration and higher resolution, which are important in the field of bioimaging. In this project, an indole-based near-infrared region II fluorescent probe that specifically recognizes hydrogen peroxide was designed and synthesized based on the Cy7 phlorocyanine dye by sequentially linking 2-methylbenzo[c,d]indole, (E)-2-chloro-3-cyclohexene-1-carboxaldehyde, and 3,6,9-trioxa-1-aminodecane with trimethyl borate as the recognition group. The structure of the probe was characterized by nuclear magnetic resonance (NMR), and the imaging effect and tissue penetration ability of the probe were tested. It was found that the fluorescent probe had high imaging resolution and deep tissue penetration at the NIR-II wavelength, and exhibited high responsiveness and selectivity for hydrogen peroxide.