Recombinant Spider Silk as Mediator for One‐Step, Chemical‐Free Surface Biofunctionalization

Abstract A unique strategy for effective, versatile, and facile surface biofunctionalization employing a recombinant spider silk protein genetically functionalized with the antibody‐binding Z domain (Z‐4RepCT) is reported. It is demonstrated that Z‐silk can be applied to a variety of materials and platform designs as a truly one‐step and chemical‐free surface modification that site specifically captures antibodies while simultaneously reducing nonspecific adsorption. As a model surface, SiO₂ is used to optimize and characterize Z‐silk performance compared to the Z domain immobilized by a standard silanization method. First, Z‐silk adsorption is investigated and verified its biofunctionality in a long‐term stability experiment. To assess the binding capacity and protein–protein interaction stability of Z‐silk, the coating is used to capture human antibodies in various assay formats. An eightfold higher binding capacity and 40‐fold lower detection limit are obtained in the immunofluorescence assay, and the complex stability of captured antibodies is shown to be improved by a factor of 20. Applicability of Z‐silk to functionalize microfluidic devices is demonstrated by antibody detection in an electrokinetic microcapillary biosensor. To test Z‐silk for biomarker applications, real‐time detection and quantification of human immunoglobulin G are performed in a plasma sample and C1q capture from human serum using an anti‐C1q antibody.