Selective and Sensitive Sensing of Hydrogen Peroxide by a Boronic Acid Functionalized Metal–Organic Framework and Its Application in Live-Cell Imaging

A new boronic acid functionalized Zr­(IV) metal–organic framework having the capability of sensing H<sub>2</sub>O<sub>2</sub> in live cells is reported. The Zr-MOF bears a UiO-66 structure and contains 2-boronobenzene-1,4-dicarboxylic acid (BDC-B­(OH)<sub>2</sub>) as a framework linker. The activated Zr-UiO-66-B­(OH)<sub>2</sub> compound (called <b>1′</b>) is highly selective for the fluorogenic detection of H<sub>2</sub>O<sub>2</sub> in HEPES buffer at pH 7.4, even in the presence of interfering ROS (ROS = reactive oxygen species) and other biologically relevant analytes. The fluorescent probe was found to display extraordinary sensitivity for H<sub>2</sub>O<sub>2</sub> (detection limit 0.015 μM) in HEPES buffer, which represents a lower value in comparison to those of the MOF probes documented so far for sensing H<sub>2</sub>O<sub>2</sub> using other analytical methods. Taking advantage of its high selectivity and sensitivity for H<sub>2</sub>O<sub>2</sub> in HEPES buffer, the probe was successfully employed for the imaging of intracellular H<sub>2</sub>O<sub>2</sub>. Imaging studies with MDAMB-231 cells revealed the emergence of bright blue fluorescence after loading with probe <b>1′</b> and subsequent treatment with H<sub>2</sub>O<sub>2</sub> solution.