Boronic acid functionalized magnetic nanoparticles via thiol–ene click chemistry for selective enrichment of glycoproteins

Abstract

A simple, novel approach was developed for the preparation of boronic acid functionalized Fe₃O₄ magnetic nanoparticles (MNPs) via thiol–ene (TE) click reaction. In this work, two clickable Fe₃O₄ MNPs functionalized with either alkene or thiol moieties were synthesized. Firstly, Fe₃O₄ MNPs were synthesized through a solvothermal method and then the clickable alkene- or thiol-coated Fe₃O₄ MNPs were prepared by sol–gel reaction with an organosilicon coupling agent, 3-(methacryloyloxy) propyltrimethoxylsilane (MPS) or 3-mercaptopropyltriethoxysilane (MPTES). The carbon–carbon double bonds/thiol groups on the surface of the MNPs serve as clickable sites to react with 4-mercaptophenylboronic acid (4-MPBA)/3-acrylamidophenylboronic acid (AAPBA) during the subsequent TE click reaction. Finally, the high density of boronic acid ligands immobilized on the surface of the Fe₃O₄ MNPs was obtained via TE click reactions. The morphology, adsorption and recognition properties of the Fe₃O₄ MNPs were investigated by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), vibrating sample magnetometry (VSM) and X-ray photoelectron spectrometry (XPS). Four proteins, including ovalbumin (OB) and transferrin (Trf) as glycoprotein templates, and lysozyme (Lyz) and horse heart cytochrome c (Cyt C) as non-glycoprotein templates are chosen as target proteins. Two types of click-Fe₃O₄ MNP (Fe₃O₄@MPS@PBA and Fe₃O₄@SH@AAPBA) exhibit a high binding capacity and excellent specificity towards glycoproteins, and can selectively capture and separate glycoproteins from egg white samples directly. Furthermore, this work could provide a promising method of surface modification for the design of more efficient adsorbents for the isolation and enrichment of proteins from complex bio-samples.