Signal amplification for DNA detection based on the HRP-functionalized Fe3O4 nanoparticles

An electrochemical approach for the sensitive detection of sequence-specific DNA has been developed. Horseradish peroxidase (HRP) assembled on the Fe3O4 nanoparticles (NPs) were utilized as signal amplification sources. High-content HRP was adsorbed on the Fe3O4 NPs via layer-by-layer (LbL) technique to prepare HRP-functionalized Fe3O4 NPs. Signal probe and diluting probe were then immobilized on the HRP-functionalized Fe3O4 NPs through the bridge of Au NPs. Thereafter, the resulting DNA–Au–HRP–Fe3O4 (DAHF) bioconjugates were successfully anchored to the gold nanofilm (GNF) modified electrode surface for the construction of sandwich-type electrochemical DNA biosensor. The electrochemical behaviors of the prepared biosensor had been investigated by the cyclic voltammetry (CV), chronoamperometry (i–t), and electrochemical impedance spectroscopy (EIS). Under optimal conditions, the proposed strategy could detect the target DNA down to the level of 0.7 fmol with a dynamic range spanning 4 orders of magnitude and exhibited excellent discrimination to two-base mismatched DNA and non-complementary DNA sequences.