Design of electrochemical biosensors with peptide probes as the receptors of targets and the inducers of gold nanoparticles assembly on electrode surface

We reported a general way to design electrochemical biosensors with peptide probes as the receptors of targets and the inducers of gold nanoparticles (AuNPs) assembly on electrode surface. To demonstrate the feasibility of our strategy, human chorionic gonadotropin (hCG) was first determined as a model analyte. Specifically, the hCG-binding peptide triggered the aggregation of AuNPs in solution; by modifying the electrode with the hCG-binding peptide, the peptide-induced AuNPs assembly was achieved on the electrode surface, resulting in the formation of a network of AuNPs and a significant fall of charge transfer resistance. The attachment of hCG onto the electrode surface through the probe-target interaction made the peptide lose its ability to trigger the formation of the AuNPs-based network architecture on electrode surface, thus leading to an increased charge transfer resistance. The electrochemical impedance technique allowed for the determination of hCG with a detection limit 0.6 mIU/mL. Furthermore, the method was used to the selective detection of amyloid-β oligomer (AβO, a reliable molecular biomarker and crucial target for the diagnosis and therapeutic intervention of Alzheimer's disease). Our result indicated that the AuNPs-based colorimetric assay can be developed into a corresponding electrochemical assay with significantly improving sensitivity and selectivity. Taking advantage of the simple principle and the unique physical and chemical properties of AuNPs, our work would be valuable for the design of novel electrochemical biosensors by marrying specific receptors.