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Abstract: A simple strategy for sensitive detection of human IgG using cadmium ions-functionalized polymer nanospheres as the label is presented. The polymer nanosphere consisted of hard poly-styrene core and biocompatible poly (acrylic acid) (PAA) shell. The carboxyl groups of hydrophilic shell were used to chelated with the cadmium ions, and then conjugate with antibody (Ab2) to fabricate metal ions marked bioconjugates as the label in immunoassay. For constructing the matrix of the immunosensor, the PAA-functionalized carbon nanotubes were used to modify disposable screen printed electrodes for the immobilization of antibody (Ab1). After sandwich immunoreaction, differential pulse voltammetry was used to oxidize the conjuncted cadmium for the detection of antigen. The obtained results provided a linear response range from 0.1 to 35.0pg/mL human IgG with a lower detection limit of 0.06pg/mL, which is prominently improved in comparison with conventional immunoassay. The usage of the chelation reaction offers a simple and convenient route for the preparation of metallo-immunoassay labels, and also avoids the complicated and time-consuming dissolving of metal component for ultrasensitive determination. This approach is expected to have wide applications in protein diagnostics and bioanalysis in the future. [Copyright &y& Elsevier]

Abstract: This paper describes the combination of electrochemical immunosensor using gold nanoparticles (GNPs)/carbon nanotubes (CNTs) hybrids platform with horseradish peroxidase (HRP)-functionalized gold nanoparticle label for the sensitive detection of human IgG (HIgG) as a model protein. The GNPs/CNTs nanohybrids covered on the glass carbon electrode (GCE) constructed an effective antibody immobilization matrix and made the immobilized biomolecules hold high stability and bioactivity. Enhanced sensitivity was obtained by using bioconjugates featuring HRP labels and secondary antibodies (Ab2) linked to GNPs at high HRP/Ab2 molar ratio. The approach provided a linear response range between 0.125 and 80ng/mL with a detection limit of 40pg/mL. The immunosensor showed good precision, acceptable stability and reproducibility and could be used for the detection of HIgG in real samples, which provided a potential alternative tool for the detection of protein in clinical laboratory. [Copyright &y& Elsevier]