To detect gatifloxacin(GAT)residue in swine urine,an electrochemical immunoassay was established.An indirect competitive immunoassay was developed,in which the coating antigen is immobilized in an enzyme-linked immunosorbent assay(ELISA)plate and GAT residue from the sample competes with the limited binding sites in added anti-GAT antibody.Horseradish peroxidase(HRP)conjugated to goat anti-rabbit IgG was used as the enzymatic label.A carbon fiber working electrode was constructed and current signals were detected by using hydrogen peroxide as a substrate and hydroquinone as an electrochemical mediator.The electrochemical immunoassay was evaluated by analysis of GAT in buffer or swine urine and an average value of half inhibition concentration(IC50)of 8.9 ng/ml was obtained.Excellent specificity of the antibody was achieved with little cross-reaction with lomefloxacin(3.0%),ciprofloxacin(3.0%),and ofloxacin(1.9%)among commonly used(fluoro)quinolones.In conclusion,the immunoassay system developed in this research can be used as a rapid,powerful and on-site analytical tool to detect GAT residue in foods and food products.
Jian YIMeng MENGZhong-qiu LIUJin-fang ZHIYuan-yang ZHANGJing XUYa-bin WANGJin-ting LIURi-mo XI
Based on the preparation of an anti-diethylstilbestrol(DES) monoclonal antibody,a simple and convenient indirect competitive enzyme-linked immunosorbent assay(ELISA) method for DES detection has been developed.The monoclonal antibody demonstrated high sensitivity to DES with an IC50 value of 275 pg mL-1 and detection limit(LOD) of 90 pg mL-1.The specificity of the assay was studied by measuring cross-reactivity of the antibody with structurally related compounds of ethinyl estradiol(<7%),estrone(<0.1%),estriol(<0.1%),and diethylstilbestrol benzoate(<0.1%).Chicken,fish,shrimp,urine and bile spiked with different concentration of DES were detected by the developed method,and the recovery rates were greater than 79.5%.Intra-and inter-assay variations were about 6%.This method exhibited high stability with a coefficient of variation less than 10% in buffer and in real samples.The LODs in fish/shrimp,liver,feed and urine spiked with DES were 600,600,4800 and 600 pg mL-1,respectively.These results confirmed that the antibody to DES was successfully produced and could be used to establish ELISA methods for DES detection in food producing animals.
