Boronic acid modified magnetic nanoparticles for enrichment of glycoproteins via azide and alkyne click chemistry

In this study, a novel approach was developed to synthesize aminophenylboronic acid functionalized magnetic nanoparticles (NPs) via Cu(I)-catalyzed azide–alkyne cycloaddition (CuAAC) 'click' chemistry. Firstly, azide-functional Fe3O4 NPs were obtained by a two-step chemical modification process. Then, an alkyne-phenylboronic acid molecule was connected onto the surface of magnetite by the CuAAC reaction. The morphology, structure and composition of the synthesized nanocomposites were characterized by transmission electron microscopy (TEM), X-ray powder diffraction (XRD), vibrating sample magnetometer (VSM), Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectrometry (XPS). Five proteins, including ovalbumin (OB), transferrin (Trf), as glycoprotein templates and lysozyme (Lyz), bovine serum albumin (BSA), horse heart cytochrome c (Cyt C) as nonglycoprotein templates are chosen as target proteins. The as-prepared click-Fe3O4@APBA NPs with a mean diameter of 23.2 nm showed a strong magnetic response to an externally applied magnetic field and exhibited a high adsorption capacity and excellent specificity towards glycoproteins in comparison with nonglycoproteins. The click-Fe3O4@APBA NPs showed the higher adsorption capacity towards glycoproteins than the nonclick-Fe3O4@APBA NPs which were synthesized through a common nucleophilic substitution reaction. The greatly enhanced adsorption capacity towards glycoproteins demonstrated that the 'click' method presented great superiority in ligand immobilization. Finally, the click-Fe3O4@APBA NPs could efficiently enrich glycoproteins from real egg white samples as well.