Recently, we reported autodisplayed Z-domains on E.coli can highly improve the sensitivity of immunoassays through the orientation control of detection antibodies [1-3]. In this work, the amperometric analysis was applied to the immunoassay based on E.coli cells with autodisplayed Z-domains. For amperometric analaysis, the reduction current of 3,5,3′,5′-tetramethylbenzidine (TMB) was measured at the potential of -50 mV and the correlation between the reduction current and the OD value was estimated to be 28 nA/OD and the limit of detection was calculated to be 0.07 in OD unit. In this work, an immunoassay was prepared by immobilizing anti-HRP antibodies to E.coli cells with autodisplayed Z-domains and the amperometric analysis was demonstrated the quantification of bound HRP. For the demonstration of medical diagnosis, C-reactive protein (CRP) was detected by using electrochemical ELISA based on E.coli with autodisplayed Z-domains.
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