Human serum albumin-based supramolecular host–guest boronate probe for enhanced peroxynitrite sensing

Peroxynitrite (ONOO⁻) is an important oxygen/nitrogen reactive species implicated in a number of physiological and pathological processes. However, due to the complexity of the cellular micro-environment, the sensitive and accurate detection of ONOO⁻ remains a challenging task. Here, we developed a long-wavelength fluorescent probe based on the conjugation between a TCF scaffold and phenylboronate; the resulting conjugate is capable of supramolecular host–guest assembly with human serum albumin (HSA) for the fluorogenic sensing of ONOO⁻. The probe exhibited an enhanced fluorescence over a low concentration range of ONOO⁻ (0–9.6 μM), whist the fluorescence was quenched when the concentration of ONOO⁻ exceeded 9.6 μM. In addition, when human serum albumin (HSA) was added, the initial fluorescence of the probe was significantly enhanced, which enabled the more sensitive detection of low-concentrations of ONOO⁻ in aqueous buffer solution and in cells. The molecular structure of the supramolecular host–guest ensemble was determined using small-angle X-ray scattering.