M13 Bacteriophage‐Activated Superparamagnetic Beads for Affinity Separation

Abstract The growth of the biopharmaceutical industry has created a demand for new technologies for the purification of genetically engineered proteins.The efficiency of large‐scale, high‐gradient magnetic fishing could be improved if magnetic particles offering higher binding capacity and magnetization were available. This article describes several strategies for synthesizing microbeads that are composed of a M13 bacteriophage layer assembled on a superparamagnetic core. Chemical cross‐linking of the pVIII proteins to a carboxyl‐functionalized bead produces highly responsive superparamagnetic particles (SPM) with a side‐on oriented, adherent virus monolayer. Also, the genetic manipulation of the pIII proteins with a His₆ peptide sequence allows reversible assembly of the bacteriophage on a nitrilotriacetic‐acid‐functionalized core in an end‐on configuration. These phage–magnetic particles are successfully used to separate antibodies from high‐protein concentration solutions in a single step with a >90% purity. The dense magnetic core of these particles makes them five times more responsive to magnetic fields than commercial materials composed of polymer–(iron oxide) composites and a monolayer of phage could produce a 1000 fold higher antibody binding capacity. These new bionanomaterials appear to be well‐suited to large‐scale high‐gradient magnetic fishing separation and promise to be cost effective as a result of the self‐assembling and self‐replicating properties of genetically engineered M13 bacteriophage.