A highly sensitive electrochemical immunosensor for hepatitis B virus surface antigen detection based on...

Here we prepared an electrochemical immunosensor employing Au sheet as working electrode, Fe₃O₄ magnetic nanoparticles (MNPs) as supporting matrix and hemin/G-quadruplex DNAzyme as signal amplifier for determination of hepatitis B virus surface antigen (HBsAg). First, the primary antibody of HBs (Ab₁) was immobilized on the surface of the carboxyl-modified MNPs. Then, the assembly of antibody and alkylthiol/G-quadruplex DNA/hemin on gold nanoparticles was used as bio-bar-coded nanoparticle probe. Protein target was sandwiched between the primary antibody of HBs (Ab₁) immobilized on the MNPs and hemin bio-bar-coded AuNPs probe labeled antibody (Ab₂). Hemin/G-quadruplex structure as HRP mimicking-DNAzyme significantly improved the catalytic reduction of H₂O₂ by oxidation of methylene blue (MB). Square wave voltammetry signals of MB provided quantitative measurements of HBsAg with a linear concentration range of 0.3-1000 pgmL^-1 and detection limit of 0.19 pgmL^-1. Due to efficient catalytic activity of HRP mimicking-DNAzyme, the proposed immunosensor exhibited high sensitivity and it holds great promise for clinical application and provides a new platform for immunosensor development and fast disease diagnosis.