Surface-enhanced Raman scattering nanoprobes for the simultaneous detection of endogenous hypochlorous acid and peroxynitrite in living cells

Hypochlorous acid (HOCl) and peroxynitrite (ONOO⁻) are two important intracellular reactive oxygen species (ROS) as crucial mediators in diverse pathological and physiological processes. Nonetheless, many of their functions are still inexplicit due to the shortage of methods for simultaneously detecting intracellular HOCl and ONOO⁻. Here we present a novel kind of reaction-based surface-enhanced Raman scattering (SERS) nanoprobes, gold nanoparticles (AuNPs) modified with synthesized 2-mercapto-4-methoxy-phenol (MMP) and 4-mercaptophenyl boronic acid pinacol ester (MBAPE), to synchronously detect HOCl and ONOO⁻ in single living cells. Taking advantage of narrow SERS peaks for spectral multiplexing, the simultaneous detection is accomplished with the SERS variation of AuNPs/MMP/MBAPE nanoprobes caused by the respective reaction of MMP and MBAPE bonded on AuNPs with HOCl and ONOO⁻. The AuNPs/MMP/MBAPE nanoprobes demonstrate a less than 1 min response to HOCl and ONOO⁻ with a sensitivity at 10⁻⁷ M level. The presented nanoprobes also have high selectivity for HOCl and ONOO⁻ respectively, resulting from SERS fingerprinting coupling with reaction specificity. Moreover, the proposed SERS strategy can be used for the simultaneous imaging of endogenous HOCl and ONOO⁻ in a single living macrophage, showing great application potential in studies of HOCl- and ONOO⁻- involved physiological events.