title: Escherichia coli with autodisplayed Z-domain of protein A for signal amplification of SPR biosensor.
abstract: Generally, an immunoaffinity SPR biosensor detects a target analyte in a sample through highly selective adsorption by using the antigen-antibody interaction. For improving the sensitivity, various kinds of particles have been added to the already bound analytes on the SPR biosensor (sandwich assay). In this work, signal amplification was demonstrated by the expression of the IgG-binding Z-domain of protein A on the outer membrane of Escherichia coli via "Autodisplay". The amount of Z-domain of protein A expressed on the outer membrane was calculated to be 280,000 molecules per cell. In addition, the IgG-binding ability of the expressed protein was characterized using FACS analysis. The signal amplification of the SPR biosensor was performed in the sandwich assay format using a model of horseradish peroxidase (HRP); the limit of detection was determined to be significantly improved from 1 microg/ml to 1 ng/ml. Finally, myoglobin analysis was demonstrated for the medical diagnosis of cardiac diseases. The detection limit was estimated to be improved from 10 ng/ml to <1 ng/ml. These results show that Z-domain-displaying E. coli can be successfully used for the signal amplification of immunoaffinity biosensors, thereby improving the sensitivity and the limit of detection.
authors.affiliation: Institute of Pharmaceutical and Medicinal Chemistry, Heinrich Heine University, Duesseldorf, Germany.
authors.forename: Joachim
authors.initials: J
authors.lastname: Jose
authors.forename: Ji-Won
authors.initials: JW
authors.lastname: Chung
authors.forename: Byoung-Jin
authors.initials: BJ
authors.lastname: Jeon
authors.forename: Ruth Maria
authors.initials: RM
authors.lastname: Maas
authors.forename: Chang-Hoon
authors.initials: CH
authors.lastname: Nam
authors.forename: Jae-Chul
authors.initials: JC
authors.lastname: Pyun
mesh_terms: D001681:Biological Assay / Q000295:instrumentation*; D015374:Biosensing Techniques / Q000295:instrumentation* / Q000379:methods; D004867:Equipment Design; D019544:Equipment Failure Analysis; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D007118:Immunoassay / Q000295:instrumentation*; D007074:Immunoglobulin G / Q000032:analysis* / Q000378:metabolism; D015202:Protein Engineering / Q000379:methods; D017434:Protein Structure, Tertiary; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013205:Staphylococcal Protein A / Q000235:genetics / Q000378:metabolism*; D020349:Surface Plasmon Resonance / Q000295:instrumentation*
chemical_list: D007074:Immunoglobulin G; D013205:Staphylococcal Protein A