Highly Efficient Synthesis and Assay of Protein-Imprinted Nanogels by Using Magnetic Templates

We report an approach integrating the synthesis of protein-imprinted nanogels ("plastic antibodies") with a highly sensitive assay employing templates attached to magnetic carriers. The enzymes trypsin and pepsin were immobilized on amino-functionalized solgel-coated magnetic nanoparticles (magNPs). Lightly crosslinked fluorescently doped polyacrylamide nanogels were subsequently produced by high-dilution polymerization of monomers in the presence of the magNPs. The nanogels were characterised by a novel competitive fluorescence assay employing identical protein-conjugated nanoparticles as ligands to reversibly immobilize the corresponding nanogels. Both nanogels exhibited K_d <10 pM for their respective target protein and low cross-reactivity with five reference proteins. This agrees with affinities reported for solid-phase-synthesized nanogels prepared using low-surface-area glass-bead supports. This approach simplifies the development and production of plastic antibodies and offers direct access to a practical bioassay.