A homogeneous electrode-based bioelectrochemical immunoassay for human chorionic gonadotrophin

An amperometric, electrode-based technique for the quantification of human chorionic gonadotrophin (HCG) is described. Glucose oxidase and an anti-HCG monoclonal antibody are co-immobilised onto a glassy carbon electrode. The activity of the enzyme is measured electrochemically by use of an electron transfer mediator (dimethylaminomethyl ferrocene). Binding of HCG to the antibody modulates the activity of the immobilised glucose oxidase, permitting quantification of HCG. Sensitivity of the assay is 7 mIU HCG ml-1 in serum (First International Reference Preparation). Soaking in 50% ethylene glycol permits reuse of the electrode. Cross-reactivity of the electrode with other hormones has been examined.