READ BY TITLE Immunosensors for determination of carcinoembryonic antigen by using solid-phase immunoassay

Huangxian Ju, Zong Dai, Jin Chen

Department of Chemistry, Nanjng University, Nanjing 210093, China

AIM Carcinoembryonic antigen (CEA) is an acidic glycoprotein and exits in the sera of most tumor patients, so it is very significant to develop a simple immunosensor for direct determination of CEA. METHODS A thionine monolayer modified gold electrode was prepared by the covalent binding of glutaraldehyde on a cysteamine self-assembled monolayer. The immobilized thionine was used as an electron transfer mediator between H2O2 and electrode by the catalysis of horseradish peroxidase (HRP) marked on CEA antibody. So a novel thionine-H2O2-HRP enzyme link immunoassay (ELISA) was developed for CEA determination. RESULTS The thionine monolayer formed was uniform and compact. At pH 7.0 its current response to H 2O2 at the same HRP concentration was best. When the concentration of H 2O2 was kept at 4.0 mM, the response depended on only the concentration of HRP or HRP marked CEA antibody. The standard curve for CEA determination was obtained from 5 ng to 120 ng/mL under the optimal conditions. The serum samples containing CEA were determined successfully by using differential pulse voltammetry. CONCLUSIONS The determination of serum CEA level by using thionine monolayer modified gold electrode as an immunosensor is more simple and sensitive than traditional IRMA method. The thionine modified electrode can be used repeatedly and miniaturized easily and has no contamination to sample, for which the method has a wide application perspective for continuous determination of CEA in clinical detection. It also provides a valuable method for the diagnosis and monitoring of carcinoma and its metastasis.

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Paper presented at the International Symposium on Predictive Oncology and Intervention Strategies; Paris, France; February 9 - 12, 2002; in the section on Prognostic Markers.