Immunofluorescence assay of pesticides on the base of immobilized multi-polyclonal antibody

Abstract

The sensitive competitive immunofluorescence method for simultaneous determination of paraoxon and dichlorvos with immobilized multi-polyclonal antibody on magnetic nanoparticles was developed. The multi-polyclonal antibody was obtained after the immunization of mixture of two prepared immunogens dichlorvos-cBSA and paraoxon-BSA (1:1). The immunogens dichlorvos-cBSA and paraoxon-BSA were synthesized preliminary. Multi-polyclonal antibody against dichlorvos and paraoxon was covalently coupled on magnetic nanoparticles. The competitive fluorescence conjugates dichlorvos-cBSA-FITC and paraoxon-BSA-ATTO 620 were synthesized. Two typical calibration curves of immunofluorescence assay for determination of dichlorvos and paraoxon in buffer solutions were obtained. The linear interval from 2 to 200 ng/mL for these two pesticides was determined. Then the calibration curves for dichlorvos and paraoxon were obtained in cow milk solutions. The linear range of pesticides in cow milk was determined (from 5 to 300 ng/L) and the detection limit for paraoxon (3.5 ng/mL) and dichlorvos (4 ng/mL) was found. The obtained results for cow milk samples were compare with results in UHT, pasteurized cow milk, sheep and goal milk. Quite different are the results when analyzing paraoxon and dichlorvos in standard solutions prepared in sheep's milk. The linear working range for the two pesticides is between 7 and 300 ng/mL it is obviously, that there is a shift of all analytical characteristics up to higher values. The reason for this is the high fat content of sheep's milk. The obtained results were showed that the developed method was 2 time more sensitive than method with the results obtained with mixture (1:1) of two separated antibodies – anti-paraoxon and anti-dichlorvos. These results confirmed the potential of the immunoassay for quantitative simultaneous screening of both dichlorvos and paraoxon. Practical applications:The use of immunofluorescence assay based on immobilized multi-polyclonal antibody on magnetic nanoparticles allows us to detect simultaneous paraoxon and dichlorovos in raw milk and ather diary products.