Signal amplification for impedimetric genosensing using gold-streptavidin nanoparticles

Abstract

Streptavidin-coated gold nanoparticles (strept-AuNPs) were used in this work to amplify the impedimetric signal generated in a biosensor detecting the DNA hybridization event. Probe oligomer was adsorbed onto a graphite epoxy composite (GEC) electrode surface and the impedance measurement was performed in a solution containing the redox marker ferrocyanide/ferricyanide. The biotinylated complementary oligomer was used as target. The change of interfacial charge transfer resistance (R_ct), experimented by the redox marker, was recorded to confirm the hybrid formation. The addition of strept-AuNPs, binding to the target due to the strong streptavidin–biotin interaction, led to a further increment of R_ct thus obtaining significant signal amplification. Strept-AuNPs on the electrode surface were observed by scanning electron microscopy (SEM) after silver enhancement treatment. A competitive binding assay was also performed using unlabelled DNA target to demonstrate its applicability to real sample analysis.