Electrochemical Detection of Cardiac Biomarker Troponin I at Gold Nanoparticle-Modified ITO Electrode by Using Open Circuit Potential

Gold nanoparticles (GNPs) have been electrodeposited on indium tin oxide (ITO) and applied to detect molecular interaction between antigen and antibody by measuring open circuit potential (OCP). As a capture protein for immunoassay, specific monoclonal antibody against human cardiac troponin I (cTnI) was modified on the GNP coated ITO electrode surface by self-assembly and characterized by electrochemical techniques. This is a simple, stable, and repeatable approach. The modified electrode can be used to detect human cTnI. In this study, we adopted a new strategy to get an electrical signal due to the enzyme-based immunecatalytic reaction by measuring the changes of OCP. This novel approach can be applied to a simplified and miniaturized diagnostic system. A linear dependence of OCP changes according to cTnI concentrations is observed in the range of concentration from 1 to 100 ng/ml. Because the clinical borderline of cTnI between normal and patient is 0.5 to 2.0 ng/ml, our results indicate that the new approach using OCP changes has a great potential for clinical diagnostic application.