Reaction-based SERS nanosensor for monitoring and imaging the endogenous hypochlorous acid in living cells

Hypochlorous acid (HOCl), as an important reactive oxygen species (ROS), is involved with many pathological and physiological pathways, whereas many aspects of its roles remain unclear due to the lack of robust analytical methods. In this work, we report a novel kind of special reaction-based nanosensors, gold nanoparticles modified with newly synthesized 2-mercapto-4-methoxy-phenol molecules (AuNPs/MMP), to detect the endogenous HOCl in living cells according to the changes in the SERS spectrum of AuNPs/MMP resulting from the reaction of HOCl with MMP on AuNPs. These nanosensors can rapidly respond to HOCl within 1 min with the detection limit at 10⁻⁷ M level. Furthermore, the nanosensors exhibit high selectivity for HOCl because of the specificity of the reaction combined with the fingerprinting capability of SERS. Consequently, the proposed SERS nanosensors are capable of monitoring and imaging the endogenous HOCl generated in a living macrophage under stimulation, showing great promise to be used for in-situ studies of the pathophysiological processes that involve HOCl.