Real-time immunoassay with a PDMS–glass hybrid microfilter electro-immunosensing chip using nanogold particles and silver enhancement

This paper presents the development of a PDMS–glass hybrid electro-immunosensing chip for real-time measurement of an antigen–antibody reaction through an electrical signal. Using a microfilter and microbeads, the antigen was easily immobilized in the detection zone where the microelectrodes were located. The immuno-reaction was detected by measuring the electrical resistance between microelectrodes using gold nanoparticles with silver enhancement. An immunoassay test with the developed chip was performed for the antigen of protein A, the specific first antibody of anti-protein A, the nonspecific first antibody of HBsAg monoclonal IgG, and the second antibody anti-rabbit IgG. The electro-immunosensing chip reduced the antigen–antibody reaction time to 10 min, thus reducing the overall assay time to about 1 h. The electrical resistance varied according to the concentration of the specific first antibody, the detection limit of which was 10 ng/ml. Compared to conventional enzyme-linked immunosorbent assays (ELISAs), the process of performing an immunoassay using the electro-immunosensing chip was relatively simple and required less time to complete. In addition, the electro-immunosensing chip required less sample volume.