Antibody-biotemplated HgS nanoparticles: Extremely sensitive labels for atomic fluorescence spectrometric immunoassay

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Abstract
In this work, antibody goat anti–human IgG as a scaffold was employed for the synthesis and biofunctionalization of HgS nanoparticles (NPs) via a facile one-pot process. After a complete sandwich-type immunoreaction among primary antibody, human IgG and secondary antibody labeled with HgS NPs, a large number of mercury ions released from captured HgS NPs dissolution were quantitatively detected by chemical vapor generation atomic fluorescence spectrometry (CVG-AFS). Taking advantage of the signal amplification property of HgS NPs and the high sensitivity of CVG-AFS, the assay detected human IgG with a limit of detection (S/N = 3) of 0.6 ng mL−1 (4.0 fmol mL−1 or 0.4 fmol) and the response was linear over a dynamic range from 1.0 to 5.0 × 104 ng mL−1 with a correlation coefficient of 0.996. A relative standard deviation (RSD) of 1.0 × 102 ng mL−1 human IgG was 1.5% for within-batch (intra-assay) and 4.5% for between-batch (inter-assay). Other proteins, such as goat anti-rabbit IgG, goat anti-human IgG, rabbit anti-human IgG, carcinoembryonic (CEA), α-fetoprotein (AFP), human serum albumin (HSA) and bovine serum albumin (BSA) did not significantly interfere with the assay for human IgG. The analytical result of HgS NPs with AFS-based immunoassay technology for the quantification of human IgG in human serum from patients is in good agreement with the result obtained by conventional immunoturbidimetric method. The consequence shows that the novel immunosensor possessed satisfactory precision, extremely high sensitivity, high selectivity and could be applied for the quantification analysis of real samples.

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