Development of a radioiodinated boronic acid probe for the detection of hydrogen peroxide and peroxynitrite

Hydrogen peroxide and peroxynitrite play important roles as signaling molecules to maintain the biological functions; however, excess levels of these oxidants are associated with various diseases. Despite their important roles <i>in vivo</i>, effective methods to measure these oxidants in the body with high sensitivity have not yet been established. Therefore, in this study, we aimed to design a radioiodinated boronic acid probe for the <i>in vivo</i> detection of hydrogen peroxide and peroxynitrite. The probe contained boronic acid, a well-known substructure that reacts with hydrogen peroxide and peroxynitrite, at positions 3 and 6 of the xanthene moiety and radioiodine at the phthalide moiety of fluorescein. I-125 labeling was successful, resulting in a radiochemical yield of 60% and radiochemical purity of >95%. <i>In vitro</i> selectivity studies demonstrated that the probe showed significant responses to both hydrogen peroxide and peroxynitrite while exhibiting minimal reactivity toward other reactive oxygen species including superoxide, nitric oxide, and peroxy radicals. In biodistribution studies using lipopolysaccharide (LPS)-treated mice generating reactive oxidants, the boronic acid probe was significantly accumulated in various organs damaged by LPS. However, this phenomenon was inhibited by administration of the antioxidant, <i>N</i>-acetylcysteine, to LPS-treated mice. These results highlight the potential of the developed radioiodinated boronic acid probe to detect hydrogen peroxide and peroxynitrite in living organisms, suggesting it as a candidate for the <i>in vivo</i> detection and functional evaluation of these oxidants in various diseases.