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▲ [6p-PB6-15] A simple platinum nanoparticles based electrochemical immunoassay for sensitive detection of human chorionic gonadotropin hormone using open circuit potential
キーワード：Platinum nanoparticles, Open circuit potential, human chorionic gonadotropin hormone
In this work, we proposed a new simple method for immunoassay based on platinum nanoparticles (PtNPs) labeled antibody followed by measuring open circuit potential (OCP). OCP is one of electrochemical techniques that does not require any voltage scan nor electric current during measurement. This not only simplifies the measurement considerably, but also makes it possible to attain an even higher sensitivity to the amount of charge transferred. Previously, we have reported the immunoassay based on gold nanoparticles (AuNPs) labeled antibody with electrochemical pre-oxidation and reduction processes followed by OCP measurement [1]. However, this method requires the application of both oxidation and reduction potentials to achieve detectable signal, which makes it not simplified as OCP method should be. Therefore, the new simple electrochemical immunoassay based on PtNPs was developed in this research. The detection of human chorionic gonadotropin hormone (hCG) was developed by direct electrical detection of PtNPs in hydrazine solution using OCP measurement without any application of external potential procedure. After preparation of sandwich-type immunosystem, hydrazine solution was dropped on electrosurface, followed by electrical detection using OCP immediately. The change of OCP signal was resulted by electrocatalytic oxidation of hydrazine on PtNPs as shown in Fig.1. The potential was shifted to negative direction with increasing of hCG concentration. For the optimization, the pH of 6.0 and hydrazine concentration of 1 mM provided the highest potential change. Under the optimal condition, a detection limit of 0.28 ng/mL and a linearity of 0-10 ng/mL were obtained. Our proposed PtNPs based method shows simpler electrochemical detection procedure than those obtained from AuNPs based method with an acceptable sensitivity and reproducibility. Moreover, it could be applied to a simplified and miniaturized diagnostic system with minimal user manipulation.