A competitive immunoassay for ultrasensitive detection of Hg2+ in water, human serum and urine samples using immunochromatographic test based on surface-enhanced Raman scattering

• The proposed ICT was able to directly detect Hg2+ without formation of Hg2+-ligand complex.
• The proposed ICT exhibited high sensitivity, specificity, stability, precision and accuracy for Hg2+ detection.
• The proposed ICT was applicable for the detection of trace amount of Hg2+ in water, human serum and urine samples.

An immunochromatographic test (ICT) strip was developed for ultrasensitive competitive immunoassay of Hg2+. This strategy was achieved by combining the easy-operation and rapidity of ICT with the high sensitivity of surface-enhanced Raman scattering (SERS). Monoclonal antibody (mAb) against Hg2+ and Raman active substance 4-mercaptobenzoic acid (MBA) dual labelled gold nanoparticles (GNPs) were prepared as an immunoprobe. The Raman scattering intensity of MBA on the test line of the ICT strip was measured for quantitative determination of Hg2+. The ICT was able to directly detect Hg2+ without complexing due to the specific recognition of the mAb with Hg2+. The IC50 and limit of detection (LOD) of the assay for Hg2+ detection were 0.12 ng mL−1 and 0.45 pg mL−1, respectively. There was no cross-reactivity (CR) of the assay with other nineteen ions and the ICT strips could be kept for 5 weeks without loss of activity. The recoveries of the assay for water, human serum and urine samples spiked with Hg2+ were in range of 88.3–107.3% with the relative standard deviations (RSD) of 1.5–9.5% (n = 3). The proposed ICT was used for the detection of Hg2+ in urine samples collected from Occupational Disease Hospital and the results were confirmed by cold-vapor atomic fluorescence spectroscopy (CV-AFS). The assay exhibited high sensitivity, selectivity, stability, precision and accuracy, demonstrating a promising method for the detection of trace amount of Hg2+ in environmental water samples and biological serum and urine samples.

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