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Development of a High-Sensitive Immunosensor Based on Monitoring Redox Signal of Gold Nanoparticle

A high-sensitive immunosensor was developed monitoring the redox signals of Au nanoparticles in connection with disposable screen-printed carbon strips (SPCSs). All the procedures could be performed on only one strip in a volume of 2 μL solution. Additionally, the direct observation of the Au nanoparticle-labeled antigenantibody complex on the electrode surface was performed by SEM imaging. The changes in the structure of Au nanoparticles during the redox process could be monitored using the high-resolution SEM images. Our immunosensor system, a combination of the screenprinting technology, direct electrical detection of Au nanoparticles with redox enhancement, provides a promising biosensor for various applications in life sciences. The improvement of electrochemical immunosensing schemes using nanomaterials is under intense investigation towards reaching the goals of better sensitivity and selectivity. Au and Ag nanoparticles have been employed intensively in optical methods. The combination of Au nanoparticles and electrochemical detection methods provides a promising platform for the development of highly sensitive and convenient immunosensors. Especially, electrochemical detection methods are widely adapted to biosensor designs because of their small-scale and inexpensive instrumentation and field-portability. In our laboratory, we have recently achieved the development of disposable sensor systems based on the three-electrode type of screen-printed carbon strips (SPCSs) with a strong advantage of fabricating a large number of near identical electrodes at a low cost. With the help of our knowledge on the fabrication of disposable sensors, we designed a disposable immunosensor protocol with Au nanoparticles as illustrated in Scheme 1. The primary antibody was immobilized directly on the working electrode surface, and a series of sandwich-type immuno-reactions was performed (Scheme 1a). Then, a high potential, 1.2 V, was applied to the electrode in 0.1 M HCl for the oxidation of Au nanoparticles, called as the pre-oxidation process (1b), then, the voltammetric measurement was performed (1c).