A novel real-time immunoassay utilizing an electro-immunosensing microchip and gold nanoparticles for signal enhancement

This study focused on the development of an electro-immunosensing (EIS) microchip for real-time measurement of antibody-antigen recognition in immunoassay. Instead of the enzyme being conjugated with a secondary antibody for detection, the process of electro-immunoassay was found to be relatively simpler compared to the conventional enzyme-linked immunosorbent assay (ELISA). This novel testing method was designed using the wave impedance theory to measure the antibody-antigen recognition. Based on the phase variety in the frequency domain, the detection limit of protein A was 1 ng/mL. It was found that the antibody-antigen recognition has an obvious peak of the phase angle near 1.61 GHz. The EIS chip had higher sensitivity and a shorter assay time than the ELISA. The sensitivity of the immunoassay on the EIS chip was 100-fold higher than that of conventional enzyme-linked immunosorbent assay (ELISA). Using antibodies labelled with 13 nm gold nanoparticles (ANPs), the detection sensitivity of protein A was increased to 0.1 ng/mL. In addition, the EIS chip was capable of detecting the kinematics of antibody-antigen binding.