E. coli outer membrane with autodisplayed Z-domain as a molecular recognition layer of SPR biosensor

In this work, the Z-domain of protein A was expressed as a recombinant-fusion protein on the outer membrane of Escherichia coli by using "Autodisplay" technology, and the outer membrane with Z-domains was layered on a SPR biosensor as a highly sensitive molecular recognition layer. The outer membrane layer formation was demonstrated by using various surfaces with controlled hydrophobicity. The effect of orientation control by the outer membrane with Z-domains was estimated to have far higher sensitivity and far improved limit of detection (LOD) in comparison to the conventional immunoassay by using a model analyte, horseradish peroxidase (HRP). The SPR biosensor with the outer membrane layer was applied to the detection of C-reactive protein (CRP). From these experiments, the LOD of SPR biosensor was estimated to improve more than 100-fold compared to the SPR biosensor with the antibody-layer by physical adsorption.