title: Direct electrochemical immunoassay based on immobilization of protein-magnetic nanoparticle composites on to magnetic electrode surfaces by sterically enhanced magnetic field force.
abstract: A direct electrochemical immunoassay system based on the immobilization of alpha-1-fetoprotein antibody (anti-AFP), as a model system, on the surface of core-shell Fe(2)O(3)/Au magnetic nanoparticles (MNP) has been demonstrated. To fabricate such an assay system, anti-AFP was initially covalently immobilized on to the surface of core-shell Fe(2)O(3)/Au MNP. Anti-AFP-modified MNP (bio-nanoparticles) were then attached to the surface of carbon paste electrode with the aid of a permanent magnet. The performance and factors influencing the performance of the resulting immunosensor were studied. alpha-1-Fetoprotein antigen was directly determined by the change in current or potential before and after the antigen-antibody reaction versus saturated calomel electrode. The electrochemical immunoassay system reached 95% of steady-state potential within 2 min and had a sensitivity of 25.8 mV. The linear range for AFP determination was from 1 to 80 ng AFP ml(-1) with a detection limit of 0.5 ng AFP ml(-1). Moreover, the direct electrochemical immunoassay system, based on a functional MNP, can be developed further for DNA sensor and enzyme biosensor.
authors.affiliation: Key Laboratory of Analytical Chemistry, College of Chemistry and Chemical Engineering, Southwest University, 400700, Chongqing, PR China.
authors.forename: Dianping
authors.initials: D
authors.lastname: Tang
authors.forename: Ruo
authors.initials: R
authors.lastname: Yuan
authors.forename: Yaqin
authors.initials: Y
authors.lastname: Chai
mesh_terms: D000906:Antibodies / Q000032:analysis; D015374:Biosensing Techniques / Q000295:instrumentation / Q000379:methods; D018076:DNA, Complementary / Q000032:analysis; D004563:Electrochemistry / Q000295:instrumentation / Q000379:methods; D004566:Electrodes; D004574:Electromagnetic Fields; D004800:Enzymes, Immobilized / Q000737:chemistry; D006735:Horseradish Peroxidase / Q000737:chemistry; D007118:Immunoassay / Q000295:instrumentation / Q000379:methods; D008280:Magnetics; D016252:Microscopy, Scanning Tunneling; D053758:Nanoparticles / Q000737:chemistry*; D011506:Proteins / Q000737:chemistry*; D015203:Reproducibility of Results; D013499:Surface Properties; D000509:alpha-Fetoproteins / Q000276:immunology
chemical_list: D000906:Antibodies; D018076:DNA, Complementary; D004800:Enzymes, Immobilized; D011506:Proteins; D000509:alpha-Fetoproteins; D006735:Horseradish Peroxidase