Antigen Immobilized Nanocomposite Electrochemical Immunosensors for Ractopamine Detection

Electrochemical immunosensors for the quantitative detection of ractopamine ( RAC) have been developed. The immunosensors were composed of nanocomposites with immobilized RAC-bovine serum albumin antigens (BSAAs). RAC-BSAAs were covalently linked to multi-wall carbon nanotubes (MCNTs), which were pre-carboxylated and activated by carbodiimides. Gold nanoparticles (Au NPs) were firstly deposited by electrochemical reduction from HAuCl4 onto glassy carbon (GC) electrodes. The MCNT-RAC-BSAA conjugates were cast on GC-Au electrodes with the strong connections between Au NPs and RAC-BSAA. Then a thin film of Prussian blue was electrodeposited onto the modified electrodes to get nanocomposite immunosensors. The differential pulse voltammograms of the immunosensors showed excellent electrocatalytic responses to RAC in solutions containing K3Fe(CN)(6) as redox probes. The immunosensors demonstrated excellent RAC detection features with a broad linear range from 1 to 1000 ng/mL and a detection limit as low as 0.25 ng/mL. The tests with spiked animal feed samples showed excellent recovery of RAC.