A fluorescent ESIPT-based benzimidazole platform for the ratiometric two-photon imaging of ONOO⁻<i>in vitro</i> and <i>ex vivo</i>

Abstract

In this work, we have developed an ESIPT-based benzimidazole platform (<b>MO-E1</b> and <b>MO-E2</b>) for the two-photon cell imaging of ONOO^- and a potential ONOO^--activated theranostic scaffold (<b>MO-E3</b>). Each benzimidazole platform, <b>MO-E1-3</b>, were shown to rapidly detect ONOO^- at micromolar concentrations (LoD = 0.28 μM, 6.53 μM and 0.81 μM respectively). The potential theranostic <b>MO-E3</b> was shown to release the parent fluorophore and drug indomethacin in the presence of ONOO^- but unfortunately did not perform well <i>in vitro</i> due to low solubility. Despite this, the parent scaffold <b>MO-E2</b> demonstrated its effectiveness as a two-photon imaging tool for the ratiometric detection of endogenous ONOO^- in RAW264.7 macrophages and rat hippocampus tissue. These results demonstrate the utility of this ESIPT benzimidazole-based platform for theranostic development and bioimaging applications.