Capacitive immunoaffinity biosensor based on vertically paired ring-electrodes

• DOI: 10.1016/j.bios.2012.07.028
• Publication Date: 2012-08-16T16:02:32Z
• Authors: Ga-Yeon Lee; Yong-Hwan Choi; Ha-Wook Chung; Hyuk Ko; Sungbo Cho; Jae-Chul Pyun
• Keywords: Equipment Failure Analysis; Immunoassay; Conductometry; Reproducibility of Results; Biosensing Techniques; Equipment Design; Electric Capacitance; Electrodes; Sensitivity and Specificity; 01 natural sciences; 0104 chemical sciences

A capacitive biosensor was developed by using a vertically paired ring-electrode for the non-labeled immunoassay. The vertically paired ring-electrode was prepared by sequential deposition and etching processes. Two electrodes were layered on glass substrate by sputtering of gold layers with thicknesses of 50 nm and 100 nm, and a parylene-C film with a thickness of 550 nm was positioned between the electrode layers as a dielectric material by thermal deposition. The top layer was made by spin coating of SU-8. And then, the ring-electrodes were exposed at the wall of the layered structure by sequential etching processes. The fabricated electrodes were characterized by cyclic voltammetry of a well-known redox couple of 3,3',5,5'-tetramethylbenzidine. The non-labeled detection of antigen-antibody interaction was demonstrated by using anti-horseradish peroxidase (HRP) antibodies and C-reactive protein (CRP) as model analytes. When the model analytes were bound to the vertically paired ring-electrode, the impedance change was measured during the immunoassay steps, and the measured impedance was analyzed by using a model circuit of the ring-electrode, and the capacitance was estimated to be dependent on the adsorption of analytes between the ring-electrodes.