An electrochemical approach for biomolecules detection involving electrocatalytic gold nanoparticles

Abstract

In the last years the gold nanoparticles (AuNPs) have been used in various applications, due to their ability to provide a stable immobilization of biomolecules retaining their bioactivity, which is a major advantage for the preparation of biosensors. Moreover, they are characterized by a good biological compatibility and excellent conductivity. Various synthesis procedures have been proposed in the recent years to better control their size, morphology and surface chemistry as the main parameters that may further influence the detection process.
The present work presents some preliminary experimental results regarding the use of electrocatalytic AuNPs prepared by a microemulsion assisted photoreduction procedure (MAPR) for bioanalytical detection involving chronoamperometry, a relatively easy electrochemical technique. Screen printed carbon electrodes (SPCE) were used as electrotransducers. The capture protein has been first immobilized on the carbon working electrode through passive adsorption to bind with corresponding antigen and AuNPs labelled antibody to build a sandwich assay. The electrochemical detection is based on the catalytic ability of AuNPs towards hydrogen evolution reaction in acidic media (1M HCl solution).
A very good linearity of the cathodic current at a certain applied cathodic potential (of -1V vs. Ag ref.) against gold nanoparticles concentration has been determined. This methodology was applied to detect AuNPs as labels in an immunosandwich assay to the determination of a normal model antigen, human IgG.
A linear relationship between the cathodic current at -1V/Ag ref. and human IgG concentration was obtained, respectively:
I(mA) = 28.22 + 0.161 x [HIgG]ng/mL (1)
in the range of 0-500 ng/mL, with a correlation coefficient of 0.991.