Ultrasensitive electrochemical immunosensor for ochratoxin A using gold colloid-mediated hapten immobilization.
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.
Liu
Xue-Ping
XP
State Key Laboratory for Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082, People's Republic of China.
Deng
Ya-Juan
YJ
Jin
Xiao-Yong
XY
Chen
Li-Guo
LG
Jiang
Jian-Hui
JH
Shen
Guo-Li
GL
Yu
Ru-Qin
RQ
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
D000911:Antibodies, Monoclonal; D017979:Gold Colloid; D006241:Haptens; D007074:Immunoglobulin G; D009793:Ochratoxins; C025589:ochratoxin A; D000469:Alkaline Phosphatase