Amperometric IgG immunosensor using a tyrosinase-colloidal gold-graphite-teflon biosensor as a transducer

摘要

An IgG immunosensor using a colloidal gold-Tyrosinase-graphite-Teflon composite biosensor as an amperometric transducer is reported. Protein A was used to immobilize the antibody on the biosensor surface and a sandwich-type configuration using alkaline phosphatase (AP) labeled anti-IgG was employed. Phenyl phosphate was used as the AP-substrate, and the enzyme reaction product, phenol, was catalytically oxidized by tyrosinase to the o-quinone, which is subsequently reduced at -0.1V at the biocomposite electrode. Variables such as the concentration of phenyl phosphate, the amount of antibody attached to the electrode surface, the immersion time into a 2% BSA solution and the incubation time into IgG, protein A and AP conjugate solutions, were optimized. Electrochemical impedance spectroscopy was used to monitor all the steps involved in the preparation of the immunosensor. A linear calibration graph for IgG was obtained between 5 and 100 ng ml(-1) IgG, with a slope value of 11.8 nA ng(-1) ml, and a detection limit of 2.6 ng ml(-1). These analytical characteristics are competitive with other IgG electrochemical immunosensor designs. The developed anti-IgG (Tyr-Au-coll-graphite-Teflon) immunosensor was applied to IgG determination in a spiked serum sample with a recovery of 103 +/- 6% for a 10 ng ml(-1) concentration level.