Zwitterionic Polydopamine/Protein G Coating for Antibody Immobilization: Toward Suppression of Nonspecific Binding in Immunoassays.

For the development of immunoassays into sophisticated analyte-sensing methods, it is a priority to suppress nonspecific binding in immunoassays. Herein, we report a one-step surface coating method that can not only optimally immobilize antibodies but also suppress nonspecific binding. Zwitterionic dopamine ( ZW -DOPA) exhibits distinct antifouling performance, and protein G enables an antibody to have an optimal orientation. A mixture of ZW -DOPA and protein G can be simply coated onto various kinds of surfaces, and the antibody can be immobilized onto the ZW -DOPA/protein G-coated surfaces. The antifouling property of the zwitterionic group, surface-independent coating property of the catechol and amine groups, and antibody-retaining property of protein G synergistically contribute to surface-independent and oriented immobilization of antibodies without nonspecific binding. The surface characteristics of ZW -DOPA/protein G-coated substrates were analyzed by X-ray photoelectron spectroscopy, contact angle goniometry, atomic force microscopy, and ellipsometry. Importantly, the ZW -DOPA/protein G-coated substrates showed high resistance to nonspecific protein adhesion. We also verified that antibodies could be immobilized onto ZW -DOPA/protein G-coated substrates using fluorescence and biolayer interferometry systems. Finally, ZW -DOPA/protein G-coated substrates were employed as immune substrates for influenza virus detection via the naked eye and surface-enhanced Raman scattering, allowing us to efficiently identify the virus. It is anticipated that the developed ZW -DOPA/protein G coating method will be useful for the advancement of immunoassays.