title: Ultrasensitive electrochemical immunosensor for ochratoxin A using gold colloid-mediated hapten immobilization.
abstract: A convenient, specific, and highly sensitive electrochemical immunosensor based on an indirect competitive assay format was developed for the determination of ochratoxin A (OTA), a common toxic contaminant in various kinds of agricultural products. The sensing substrate was prepared using a gold electrode modified with a self-assembled monolayer of 1,6-hexanedithiol that mediated the assembly of a gold colloid layer, which could enhance the surface loading of OTA-ovalbumin conjugate and improve the sensitivity in electrochemical readouts. After competition of the limited anti-OTA mouse monoclonal antibody between immobilized hapten and OTA analyte in sample solution, alkaline phosphatase (ALP)-labeled horse anti-mouse immunoglobulin G (IgG) antibody was selectively bound onto the surface of the electrode, affording an indicator for OTA concentration in the sample. Electrochemical response arising from the oxidation of enzymatic product of 1-naphthyl phosphate was observed to be inversely proportional to OTA concentration in the range from 10 pg/ml to 100 ng/ml with a detection limit as low as 8.2 pg/ml. Furthermore, a negligible matrix effect and good recoveries were obtained in the determination of corn samples, evidencing the feasibility of the proposed method for accurate determination of OTA in corn samples.
authors.affiliation: State Key Laboratory for Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082, People's Republic of China.
authors.forename: Xue-Ping
authors.initials: XP
authors.lastname: Liu
authors.forename: Ya-Juan
authors.initials: YJ
authors.lastname: Deng
authors.forename: Xiao-Yong
authors.initials: XY
authors.lastname: Jin
authors.forename: Li-Guo
authors.initials: LG
authors.lastname: Chen
authors.forename: Jian-Hui
authors.initials: JH
authors.lastname: Jiang
authors.forename: Guo-Li
authors.initials: GL
authors.lastname: Shen
authors.forename: Ru-Qin
authors.initials: RQ
authors.lastname: Yu
mesh_terms: D000469:Alkaline Phosphatase / Q000737:chemistry; D000911:Antibodies, Monoclonal / Q000737:chemistry / Q000276:immunology; D015374:Biosensing Techniques / Q000379:methods*; D004563:Electrochemistry / Q000379:methods*; D017979:Gold Colloid / Q000737:chemistry*; D006241:Haptens / Q000737:chemistry; D007118:Immunoassay / Q000379:methods*; D007074:Immunoglobulin G / Q000737:chemistry / Q000276:immunology; D009793:Ochratoxins / Q000032:analysis* / Q000276:immunology; D015203:Reproducibility of Results
chemical_list: D000911:Antibodies, Monoclonal; D017979:Gold Colloid; D006241:Haptens; D007074:Immunoglobulin G; D009793:Ochratoxins; C025589:ochratoxin A; D000469:Alkaline Phosphatase