A magnetite suspension-based washing method for immuoassays using Escherichia coli with autodisplayed Z-domains

Kim D-H, Bong J-H, Yoo G, Chang S-Y, Chang YW, Kang M-J, Jose J, Pyun J-C

Abstract

tEscherichia coli cells with autodisplayed Z-domains have been used for immunoassays of specific tar-get analytes. In this study, a magnetite suspension was used for the washing step in immunoassays ofE. coli cells with autodisplayed Z-domains. This approach enhanced the washing conditions for theseimmunoassays by determining (1) the optimal concentration of the magnetite suspension, (2) the capac-ity of the magnetite suspension-based washing method to recover E. coli cells, and (3) the level at whichthe activity of autodisplayed Z-domains is maintained. In immunoassays of C-reactive protein (CRP),the immunoassay incorporating the magnetite suspension-based washing method showed a sensitivityand limit of detection considerably higher than those of the conventional centrifugation-based wash-ing method. The results indicated that immunoassays incorporating the magnetite suspension-basedwashing method are effective for medical diagnoses based on CRP assay.