Nanozyme mediated Raman-NLISA dual-modal immunosensor for accurate and sensitive detection of microcystin-LR.

A Raman scattering and nanozyme-linked immunosorbent assay (NLISA) dual modal immunosensor, was constructed by mesoporous SiO2/Au-Pt nanozymes (m-SAP) and nanobodies (A2.3-SBP). Oxidized TMB served as Raman and ELISA signals in a competitive binding assay. Under optimized conditions, an inverse correlation was established between the Microcystin-LR (MC-LR) concentration and the signals, spanning Raman and ELISA ranges of 0.1-100 μg L-1 and 1.0-500 μg L-1, with limit of detections (LODs, 3σ/S) of 0.015 μg L-1 and 0.12 μg L-1, respectively. The LODs showed over 90 times and 11 times higher sensitivity than that of traditional ELISA (t-ELISA, LOD, 1.36 μg L-1). The immunosensor exhibited excellent accuracy in practical samples, can be integrated together for the detection of MC-LR within 45 min, which greatly short the detection time of t-ELISA (>2 h). This method displayed potential for detecting other toxins by simply changing the nanobodies.