Optimization of electrochemical analysis for signal amplification in gold nanoparticle-probed immunoassays

Abstract

Biosensing systems with integrated nanomaterials have revolutionized technological advancements in recent decades. Gold nanoparticles (AuNPs) in particular have been widely used in electrochemical sensors owing to their stability and unique characteristics. Previously, we developed biosensors that utilize the redox activity of AuNPs. In recent years, unique advances have been made by combination with other nanomaterials. However, information regarding the optimal electrochemical measurement conditions and the relationship between the electrode surface and AuNPs remain unknown. In this study, we quantitatively determined kinetic parameters such as the diffusion coefficient and electron transfer rate in the redox reaction of AuNPs on disposable screen-printed electrodes. Furthermore, the relationship between the addition of antibodies and blocking agents and the decrease in the determined parameters could be deduced. This is useful for the determination of the fine balance between the sensitivity and specificity. Limits of detection (LOD) were obtained as 5.0 fmol/L (M) for AuNPs on a bare electrode, 0.1 pM for AuNPs on an antibody-modified electrodes, and 9.3 pM for AuNPs after immunoassay, allowing discussion of the given principle limits and actual biosensor performance. Under optimal conditions, the electrochemical biosensor achieved nearly two-fold signal amplification using a reduction current after AuNPs oxidation. These findings will allow the investigation of the kinetics of AuNPs on electrodes consisting of different materials to further elucidate the framework for improved sensitivity.