An electro-active system of immuno-assay (EASI assay) utilising self assembled monolayer modified electrodes

• Published in: Biosensors & bioelectronics Vol. 16; no. 9; pp. 875 - 885
• Main Authors: Porter, Robert, van der Logt, Paul, Howell, Steven, Kyröläinen-Reay, Marika, Badley, Andy
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Lausanne Elsevier B.V 01.12.2001; Elsevier Science
• Subjects: Amino Acid Sequence; Amperometric; Animals; Antibodies, Bispecific - genetics; Base Sequence; Biological and medical sciences; Biosensing Techniques - methods; Biosensing Techniques - statistics & numerical data; Biosensor; Biosensors; Biotechnology; Camelids, New World; Carbazoles - immunology; Electrochemical; Electrochemistry; Electrodes; Electronics, Medical; Enzyme-Linked Immunosorbent Assay; Estrone - analogs & derivatives; Estrone - analysis; Estrone - immunology; Fundamental and applied biological sciences. Psychology; Immunoassay; Immunoassay - methods; Immunoassay - statistics & numerical data; Immunoglobulin Fragments - genetics; Methods. Procedures. Technologies; Molecular Sequence Data; Sensitivity and Specificity; Various methods and equipments; Immunoassay; Amperometric; Biosensor; Electrochemical; Amperometry; Electrochemistry; Immunosensor; Immunological method
• ISSN: 0956-5663; 1873-4235
• DOI: 10.1016/S0956-5663(01)00207-X

Most immunoassays currently rely on optical methods for signal generation e.g. in ELISA and rapid assay formats. It has become apparent as in the Glucose sensor market that there is a need for simple direct electrical immuno-sensors. We have investigated the novel use of organic conducting monolayers used as a direct electrochemical detection support for an immuno-reaction. It was found that antibodies raised to a carbazole dimer monolayer could increase the charge movement across that monolayer surface. Antibody fragments were taken from a specific anti-carbazole antibody fragment library and combined with an antibody fragment directed to the hormone estrone 3 glucuronide (E3G), the target antigen to form a bispecific antibody fragment. The device utilised these specific antibody fragments and incorporated them on the top plate of a capillary fill format as the immuno-assay components. The immuno-reaction utilised a competition assay. Free E3G analyte in the sample displaced the bispecific antibody fragment from the immuno-surface leaving it free to bind the carbazole monolayer surface. There the binding was detected using amperometric or coulometric methods. By combining all there element it was possible to develop a sensitive immuno-assay that could detect E3G in a reproducible calibrated fashion down to 10 ng/ml.