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

Abstract

In this work, we have developed an ESIPT-based benzimidazole platform (MO-E1 and MO-E2) for the two-photon cell imaging of ONOO⁻ and a potential ONOO⁻-activated theranostic scaffold (MO-E3). Each benzimidazole platform, MO-E1–3, were shown to rapidly detect ONOO⁻ at micromolar concentrations (LoD = 0.28 μM, 6.53 μM and 0.81 μM respectively). The potential theranostic MO-E3 was shown to release the parent fluorophore and drug indomethacin in the presence of ONOO⁻ but unfortunately did not perform well in vitro due to low solubility. Despite this, the parent scaffold MO-E2 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.