Preparation and characterization of uniformly sized molecularly imprinted polymers functionalized with core–shell magnetic nanoparticles for the recognition and enrichment of protein

Abstract

A general method to prepare thin, molecularly imprinted polymer (MIP) coatings on magnetic Fe₃O₄ nanoparticles (NPs) with a uniform core–shell structure for the recognition and enrichment of protein was developed. Four proteins (bovine serum albumin (BSA, pI = 4.9), bovine hemoglobin (BHb, pI = 6.9), bovine pancreas ribonuclease A (RNase A, pI = 9.4) and lysozyme (Lyz, pI = 11.2)) with different isoelectric points were chosen as the templates. The magnetic protein-MIPs were synthesized by combining surface imprinting and sol–gel techniques. The morphology, adsorption and recognition properties of the magnetic molecularly imprinted NPs were investigated by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared (FT-IR) spectroscopy and through the use of a vibrating sample magnetometer (VSM). In comparison with the use of Lyz, BSA and RNase A as template proteins, BHb-imprinted Fe₃O₄ showed the best imprinting effect and the highest adsorption capacity among the four proteins. The as-prepared Fe₃O₄@BHb-MIPs NPs with a mean diameter of 230 nm were coated with an MIP shell that was 10 nm thick, which enabled the Fe₃O₄@BHb-MIPs to easily reach adsorption equilibrium. A high magnetic saturation value of 25.47 emu g⁻¹ for Fe₃O₄@BHb-MIPs NPs was obtained, which endowed the adsorbent with the convenience of magnetic separation under an external magnetic field. The resultant Fe₃O₄@BHb-MIPs NPs could not only selectively extract a target protein from mixed proteins but also specifically capture the protein BHb from a real sample of bovine blood. In addition, different batches of magnetic MIPs showed good reproducibility and reusability for at least six repeated cycles.