title: Novel amperometric immunosensor for rapid separation-free immunoassay of carcinoembryonic antigen.
abstract: A novel immunosensor for rapid separation-free determination of carcinoembryonic antigen (CEA) in human serum is proposed. The immunosensor is prepared by co-immobilizing thionine and horseradish peroxidase (HRP)-labeled CEA antibody on a glassy carbon electrode (GCE) through covalently binding them to GCE with a glutaraldehyde (GA) linkage. The electrochemical behavior of the immobilized thionine displays a surface-controlled electrode process with an average electron transfer rate constant of 4.74+/-2.99 s(-1). It can be used as an electron transfer mediator for enzymatic activity detection of the HRP-labeled antibody to CEA. After the immunosensor is incubated with CEA solution at 23 degrees C for 40 min, the access of activity center of the HRP to thionine is partly inhibited, which leads to a linear decrease in the catalytic efficiency of the HRP to the oxidation of immobilized thionine by H(2)O(2) at -300 mV over two CEA concentration ranges from 0.5 to 3.0 and 3.0 to 167 ng/ml. Under optimal conditions, the detection limit for the CEA immunoassay is 0.1 ng/ml at three times background noise. The immunosensor shows good accuracy and acceptable storage stability, precision and reproducibility with intra-assay CVs of 6.1% and 5.8% at 2.5 and 50 ng/ml CEA, respectively, and an inter-assay CV of 6.3% at 50 ng/ml. This method is economical and shortens the analytical time, making it potentially attractive for clinical immunoassays.
authors.affiliation: Department of Chemistry, Institute of Analytical Science, State Key Laboratory of Coordination Chemistry, Nanjing University, Hankou Lu, Nanjing 210093, PR China.
authors.forename: Zong
authors.initials: Z
authors.lastname: Dai
authors.forename: Feng
authors.initials: F
authors.lastname: Yan
authors.forename: Hua
authors.initials: H
authors.lastname: Yu
authors.forename: Xiaoya
authors.initials: X
authors.lastname: Hu
authors.forename: Huangxian
authors.initials: H
authors.lastname: Ju
mesh_terms: D000906:Antibodies; D015374:Biosensing Techniques / Q000295:instrumentation*; D002272:Carcinoembryonic Antigen / Q000097:blood / Q000276:immunology / Q000302:isolation & purification*; D004563:Electrochemistry / Q000295:instrumentation / Q000379:methods; D004566:Electrodes; D004800:Enzymes, Immobilized; D006735:Horseradish Peroxidase; D006801:Humans; D007118:Immunoassay / Q000295:instrumentation* / Q000379:methods*; D007124:Immunoenzyme Techniques / Q000295:instrumentation / Q000379:methods; D010640:Phenothiazines; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
chemical_list: D000906:Antibodies; D002272:Carcinoembryonic Antigen; D004800:Enzymes, Immobilized; D010640:Phenothiazines; D006735:Horseradish Peroxidase; C009469:thionine