A Mussel Adhesive Protein Fused with the BC Domain of Protein A Is a Functional Linker Material That Efficiently Immobilizes Antibodies Onto Diverse Surfaces

The efficient immobilization of antibodies onto solid surfaces is a vital factor for the sensitivity and specificity of various immunoassays and immunosensors. In the present work, we designed and produced a novel linker protein, BC-MAP, in Escherichia coli by genetically fusing mussel adhesive protein (MAP) with two domains (B and C) of protein A (antibody binding protein) for efficient antibody immobilization on diverse surfaces. Through direct surface coating analyses, we found that BC-MAP successfully coated diverse surfaces including glass, polymers, and metals, but the BC domain alone did not. Importantly, antibodies were efficiently immobilized on BC-MAP-coated surfaces, and the immobilized antibodies interacted selectively with their corresponding antigen. Quartz crystal microbalance analyses showed that BC-MAP has excellent antibody-binding ability compared to BC protein on gold surfaces. These results demonstrate that the MAP domain, with uniquely strong underwater adhesive properties, plays a role in the direct and efficient coating of BC-MAP molecules onto diverse surfaces lacking any additional surface treatment, and the BC domain of BC-MAP contributes to the selective and oriented immobilization of antibodies on BC-MAP-coated surfaces. Thus, our BC-MAP fusion protein could be a valuable novel linker material for the facile and efficient immobilization of antibodies onto diverse solid supports.