Magnetic Affinity Immunoassay Based Enzyme-labeled Phage Displayed Antibody

A novel magnetic affinity immunoassay (MAIA) strategy on the basis of enzyme-labeled phage displayed antibody was developed. The assay consisted of a sandwich format in which immobilized polyclonal antibody (pcAb) on magnetic microparticle was used as capture probe, and enzyme-labeled phage displayed antibody as specific detection probe to increase enzyme amount and enhance detection signal. By the proposed method, β-bungarotoxin (β-BGT) was successfully detected. A linear relationship between absorbance value and the concentration of β-BGT in the range of 0.016–62.5 μg L−1 was obtained. The linear regression equation was Y = 0.641X + 1.355 (R = 0.9925, n = 13, p < 0.0001) with a detection limit of 0.016 μg L−1. In comparison with the traditional ELISA, this method provided a 10-fold better sensitivity in β-BGT detection. Also this method provided a 4-fold better sensitivity comparing with the MAIA based on enzyme labeled monoclonal antibody (mcAb). Due to the low detection limit, high accuracy and specificity, this method holds great promise in toxin trace detection.

The novel method consisted of a sandwich format in which immobilized polyclonal antibody on magnetic microparticle was used as capture probe and enzyme-labeled phage displayed antibody as detection probe to increase the enzyme amount and enhance detection signal. Toxin was detected with a “magnetic capturing probe-toxin-HRP-phageantibody” immune-complex model, and the concentration of toxin was determined by chromogenic reaction.Figure optionsDownload full-size imageDownload as PowerPoint slide