Evaluation of borinic acids as new, fast hydrogen peroxide-responsive triggers.

Gatin-Fraudet, Blaise; Ottenwelter, Roxane; Le Saux, Thomas; Norsikian, Stéphanie; Pucher, Mathilde; Lombès, Thomas; Baron, Aurélie; Durand, Philippe et al. · Proc Natl Acad Sci U S A · 2021

basic_science · Level V

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Abstract

Hydrogen peroxide (H<sub>2</sub>O<sub>2</sub>) is responsible for numerous damages when overproduced, and its detection is crucial for a better understanding of H<sub>2</sub>O<sub>2</sub>-mediated signaling in physiological and pathological processes. For this purpose, various "off-on" small fluorescent probes relying on a boronate trigger have been prepared, and this design has also been involved in the development of H<sub>2</sub>O<sub>2</sub>-activated prodrugs or theranostic tools. However, this design suffers from slow kinetics, preventing activation by H<sub>2</sub>O<sub>2</sub> with a short response time. Therefore, faster H<sub>2</sub>O<sub>2</sub>-reactive groups are awaited. To address this issue, we have successfully developed and characterized a prototypic borinic-based fluorescent probe containing a coumarin scaffold. We determined its in vitro kinetic constants toward H<sub>2</sub>O<sub>2</sub>-promoted oxidation. We measured 1.9 × 10<sup>4</sup> m<sup>-1</sup>⋅s<sup>-1</sup> as a second-order rate constant, which is 10,000-fold faster than its well-established boronic counterpart (1.8 m<sup>-1</sup>⋅s<sup>-1</sup>). This improved reactivity was also effective in a cellular context, rendering borinic acids an advantageous trigger for H<sub>2</sub>O<sub>2</sub>-mediated release of effectors such as fluorescent moieties.