Graphene oxide-based boronate polymer brushes via surface initiated atom transfer radical polymerization for the selective enrichment of glycoproteins

Biomedical sciences, and in particular biomarker research, demand efficient glycoprotein enrichment platforms. In this work, a facile and efficient method was developed to synthesize boronic acid polymer brushes immobilized on magnetic graphene oxide via surface initiated atom transfer radical polymerization (SI-ATRP) for the selective enrichment of glycoproteins from complex biological samples. The magnetic graphene oxide (GO@Fe₃O₄) nanocomposites were prepared by a solvothermal reaction, providing an ultrahigh surface area and allowing fast separation. Through the self-assembly procedure, the pyrene-based initiators (GO@Br) of SI-ATRP were easily functionalized on the GO sheet via noncovalent π-π interaction between pyrene and GO. Finally, the well-defined and high density poly(4-vinylphenylboronic acid) brushes (GO@PVPBA) via SI-ATRP were successfully fabricated. The morphology and structure of GO@Fe₃O₄, GO@Br, and GO@PVPBA nanocomposites were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), vibrating sample magnetometry (VSM), Fourier transform-infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). The selective recognition capability of GO@PVPBA nanocomposites was demonstrated by the selective enrichment of glycoproteins from a complex system consisting of standard proteins ovalbumin (OVA), transferrin (Trf), bovine serum albumin (BSA), and lysozyme (Lyz). Furthermore, the GO@PVPBA nanocomposite also exhibited a high binding capacity up to 514.8 and 445.9 mg g^-1 for OVA and Trf, respectively, and was applied to capture directly glycoproteins from the egg white samples.