Zwitterionic polymer electroplating facilitates the preparation of electrode surface for biosensing.

Surface chemistry critically affects the diagnostic performance of biosensors. An ideal sensor surface should be resistant to nonspecific protein adsorption, yet be conducive to analytical responses. Here we report a new polymeric material, zwitterionic polypyrrole (ZiPPy), to produce optimal surface condition for biosensing electrodes. ZiPPy combines merits from two unique precursors: the zwitterionic function that efficiently hydrates electrode surface, hindering nonspecific binding of hydrophobic proteins; and the pyrrole backbone which enables rapid (<7 min), controlled deposition of ZiPPy through electropolymerization. ZiPPy-coated electrodes showed lower electrochemical impedance and less non-specific protein adsorption (low fouling), outperforming bare and polypyrrole-coated electrodes. Moreover, affinity ligands for target biomarkers could be immobilized together with ZiPPy in a single-step electropolymerization. We developed ZiPPy-coated electrodes with specificity for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The prepared sensor detected SARS-CoV-2 antibodies in human saliva down to 50 ng mL-1 , without need for sample purification or secondary labeling. This article is protected by copyright. All rights reserved.