title: An amperometric immunosensor for separation-free immunoassay of CA125 based on its covalent immobilization coupled with thionine on carbon nanofiber.
abstract: A carbon nanomaterial, soluble carbon nanofiber, was used for the first time to construct an immunosensor for a rapid separation-free immunoassay. The acidic oxidation of the carbon nanofiber provided its solubility and wettability for convenient preparation of a porous carbon nanofiber membrane and a larger number of active sites for covalent binding of carcinoma antigen-125 (CA125) and thionine as electron transfer mediator. This matrix was a suitable environment for the immobilized protein. The immobilized HRP-labeled immunoconjugate showed good enzymatic activity for the oxidation of thionine by hydrogen peroxide. With a competitive mechanism, the differential pulse voltammetric peak current of this system decreased linearly with increasing CA125 concentration (from 2 to 75 U/ml) in the incubation solution. The CA125 immunosensor showed good precision, high sensitivity, acceptable stability and reproducibility with a detection limit of 1.8 U/ml. The soluble carbon nanofiber is a novel method for preparation of immunosensors.
authors.affiliation: Key Laboratory of Analytical Chemistry for Life Science (Education Ministry of China), Department of Chemistry, Nanjing University, Nanjing 210093, China.
authors.forename: Lina
authors.initials: L
authors.lastname: Wu
authors.forename: Feng
authors.initials: F
authors.lastname: Yan
authors.forename: Huangxian
authors.initials: H
authors.lastname: Ju
mesh_terms: D015374:Biosensing Techniques / Q000379:methods*; D002244:Carbon / Q000737:chemistry; D003217:Conductometry / Q000379:methods*; D017097:Electric Impedance; D006801:Humans; D007118:Immunoassay; D047908:Intracellular Signaling Peptides and Proteins; D049329:Nanostructures / Q000737:chemistry*; D036103:Nanotechnology / Q000379:methods; D010084:Oxidation-Reduction; D010640:Phenothiazines / Q000737:chemistry; D011506:Proteins / Q000032:analysis*
chemical_list: D047908:Intracellular Signaling Peptides and Proteins; C549756:NBR1 protein, human; D010640:Phenothiazines; D011506:Proteins; D002244:Carbon; C009469:thionine