Zwitterionic Polymer Electroplating Facilitates the Preparation of Electrode Surfaces 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 a new polymeric material, zwitterionic polypyrrole (ZiPPy), is reported to produce optimal surface condition for biosensing electrodes. ZiPPy combines two unique advantages: 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 show lower electrochemical impedance and less nonspecific protein adsorption (low fouling), outperforming bare and polypyrrole-coated electrodes. Moreover, affinity ligands for target biomarkers can be immobilized together with ZiPPy in a single-step electropolymerization. ZiPPy-coated electrodes are developed with specificity for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The prepared sensor detects SARS-CoV-2 antibodies in human saliva down to 50 ng mL(-1), without the need for sample purification or secondary labeling.

Automated summary

A new polymeric material called zwitterionic polypyrrole (ZiPPy) is reported to have optimal surface condition for biosensing electrodes. ZiPPy combines the advantages of efficient hydration of the electrode surface and rapid deposition through electropolymerization. The ZiPPy-coated electrodes show lower electrochemical impedance and less nonspecific protein adsorption, outperforming other types of electrodes. Moreover, affinity ligands can be immobilized together with ZiPPy in a single-step electropolymerization. The ZiPPy-coated electrodes specifically detect SARS-CoV-2 antibodies in human saliva without the need for sample purification or secondary labeling.