Determination of β-HCG using amperometric immunosensors based on a conducting immunocomposite Original Research Article

An amperometric immunosensor based on a rigid immunocomposite was built to measure human chorionic gonadotropin β-subunit (β-HCG). The immunocomposite is formed by a conducting graphite–methacrylate matrix containing the anti-β-HCG antibody. The main advantage of this kind of immunosensors is their easy regeneration which can be achieved by a simple polishing of their surface. β-HCG is determined with a sandwich assay using anti-β-HCG conjugate labelled with horseradish peroxidase (HRP). The extent of the immunological interaction is quantified by the activity of the labelling enzyme: peroxidase is regenerated after the enzymatic reduction of H2O2 by hydroquinone which is used as a mediator in the solution. The reduction of hydroquinone is amperometrically monitored using a potential of −0.1 V. Each assay can be realised in less than 40 min. The upper limit corresponds to a β-HCG concentration of 98.0 IU/l and the detection limit to 2.6 IU/l.