Ultralow Fouling and Functionalizable Surface Chemistry Based on a Zwitterionic Polymer Enabling Sensitive and Specific Protein Detection in Undiluted Blood Plasma

A crucial step in the development of implanted medical devices, in vivo diagnostics, and microarrays is the effective prevention of nonspecific protein adsorption from real-world complex media such as blood plasma or serum. In this work, a zwitterionic poly(carboxybetaine acrylamide) (polyCBAA) biomimetic material was employed to create a unique biorecognition coating with an ultralow fouling background, enabling the sensitive and specific detection of proteins in blood plasma. Conditions for surface activation, protein immobilization, and surface deactivation of the carboxylate groups in the polyCBAA coating were determined. An antibody-functionalized polyCBAA surface platform was used to detect a target protein in blood plasma using a sensitive surface plasmon resonance (SPR) sensor. A selective protein was directly detected from 100% human blood plasma with extraordinary specificity and sensitivity. The total nonspecific protein adsorption on the functionalized polyCBAA surface was very low (<3 ng/cm2 for undiluted blood plasma). Because of the significant reduction of nonspecific protein adsorption, it was possible to monitor the kinetics of antigen−antibody interactions in undiluted blood plasma. The functionalization effectiveness and detection characteristics using a cancer protein marker candidate of polyCBAA were compared with those of the conventional nonfouling oligo(ethylene glycol)-based surface chemistry.