Sensitive electrochemical immunoassay of IgG1 based on poly(amido amine) dendrimer-encapsulated CdS quantum dots

Abstract

Herein, we designed a new electrochemical immunoassay protocol for the detection of IgG1, as a model biomolecule, by using poly(amidoamine) dendrimer-encapsulated CdS quantum dots (DEQD) as molecular tags. Initially, monoclonal anti-human IgG1 specific antibody (mAb₁) was anchored on a bovine serum albumin-modified glassy carbon electrode preferably selective to capture F_ab of IgG1 from the sample. For the determination, monoclonal anti-human IgG1 (F_c specific) antibody (mAb₂) was covalently bound onto the as-prepared DEQD based on a typical carbodiimide coupling. With a sandwich-type immunoassay format, the subsequent anodic stripping voltammetric detection of cadmium released under acidic condition from the coupled quantum dots (QD) was conducted in 2-mL pH 2.5 HCl containing 0.01 M KCl. Under optimal conditions, the dynamic concentration range of the developed immunoassay spanned from 0.1 pg mL⁻¹ to 100 ng mL⁻¹ IgG1 with a detection limit (LOD) of 0.06 pg mL⁻¹ toward IgG1. The electrochemical immunoassay showed good reproducibility, selectivity and stability. The analysis of human serum specimens were in good accordance with the results obtained by a referenced enzyme-linked immunosorbent assay (ELISA) method.