Facile synthesis of zwitterionic polymer-coated core–shell magnetic nanoparticles for highly specific capture of N-linked glycopeptides

Abstract

Highly selective and efficient capture of glycosylated proteins and peptides from complex biological samples is of profound significance for the discovery of disease biomarkers in biological systems. Recently, hydrophilic interaction liquid chromatography (HILIC)-based functional materials have been extensively utilized for glycopeptide enrichment. However, the low amount of immobilized hydrophilic groups on the affinity material has limited its specificity, detection sensitivity and binding capacity in the capture of glycopeptides. Herein, a novel affinity material was synthesized to improve the binding capacity and detection sensitivity for glycopeptides by coating a poly(2-(methacryloyloxy)ethyl)-dimethyl-(3-sulfopropyl) ammonium hydroxide (PMSA) shell onto Fe₃O₄@SiO₂ nanoparticles, taking advantage of reflux-precipitation polymerization for the first time (denoted as Fe₃O₄@SiO₂@PMSA). The thick polymer shell endows the nanoparticles with excellent hydrophilic property and several functional groups on the polymer chains. The resulting Fe₃O₄@SiO₂@PMSA demonstrated an outstanding ability for glycopeptide enrichment with high selectivity, extremely high detection sensitivity (0.1 fmol), large binding capacity (100 mg g⁻¹), high enrichment recovery (above 73.6%) and rapid magnetic separation. Furthermore, in the analysis of real complicated biological samples, 905 unique N-glycosylation sites from 458 N-glycosylated proteins were reliably identified in three replicate analyses of a 65 μg protein sample extracted from mouse liver, showing the great potential of Fe₃O₄@SiO₂@PMSA in the detection and identification of low-abundance N-linked glycopeptides in biological samples.