Here we prepared an electrochemical immunosensor employing Au sheet as working electrode, Fe3O4 nanoparticle as supporting matrix and hemin/G-quadruplex DNAzyme as signal amplifier for determination of HBsAg. Fe3O4 nanoparticle was used for immobilization of primary antibody and protein target was sandwiched between magnetic nanoparticle and AuNP-hemin/G-quadruplex which was attached to methylene blue. Hemin/G-quadruplex structure as HRP mimicking-DNAzyme significantly improved the catalysis of H2O2 by oxidation of methylene blue. Experimental results revealed that the immunoassay enabled the determination of HBsAg with linear working ranges of 1–100 pgmL_1. The limit of detection for HBsAg is 0.46 pgmL_1.. The immunosensor exhibited high sensitivity and highly efficient catalysis of DNAzyme, showing great promise for clinical application and providing new opportunities for fast disease diagnosis.
