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.

Monodisperse magnetic gamma-Fe2O3 nanoparticles (MNPs) were prepared by a simple, improved, one-pot solvothermal synthesis using SDS and PEG 6000 as double capping reagents. This double protecting layer afforded better MNP uniformity (Z average 257 +/- 11.12 nm, PDI = 0.18) and colloidal stability. Materials were characterized by DLS, SEM, TEM, XPS, and XRD. The use of these MNPs in the synthesis of core-shell structures with uniform and tunable silica coatings was demonstrated, as silica coated MNPs are important for use in a range of applications, including magnetic separation and catalysis and as platforms for templated nanogel synthesis.