Flow-through amperometric immunosensor: fast 'sandwich' scheme immunoassay

A flow-through immunosensor based on a high-surface-area carbon immunoelectrode has been developed. Dispersed carbon material serves as a carrier for immobilized antibodies and at the same time as an electrode material. The 'sandwich' scheme of immunoassay has been used. Iodine formed as a result of the enzymatic oxidation of iodide by a peroxidase label has been detected amperometrically. The immunosensor consists of a disposable sensing element (immunocolumn) containing dispersed carbon material with immobilized antibodies which also acts as a working electrode. A current collector connects the working electrode to the measuring device. The electrochemical detection time of the peroxidase-labeled immuno-complex does not exceed several minutes. The overall time of analysis including flowing of analyte, flowing of antigen, washing and detection stages is as low as 22 min. This technique allows fast determination of rabbit IgG (used as a model analyte) with a low detection limit in the picomolar range and also the determination of human IgM in blood plasma with a low detection limit in the nanomolar range.