Magnetic nanoparticles (MNPs) coated with multilayer polysaccharide shells have been fabricated using a layer-by-layer approach via the alternate deposition of hyaluronan (HA) and chitosan (CS) onto the surface, and the hydrophilic materials were utilized for effective and selective enrichment of glycopeptides in biological samples.Protein glycosylation, one of the most important and ubiquitous post-translation modifications, plays a vital role in regulating various complex biological processes, such as cell-cell interaction, molecular recognition, protein folding, immune response and so forth. 1 Many human diseases have been found to be associated with aberrant N-glycosylation. 2 Currently, mass spectrometry (MS) based techniques have been the premier technology for the characterization of protein glycosylation. Unfortunately, inherent low abundance of glycopeptides, tremendous heterogeneity of each glycosylation site and severe ion suppression caused by the co-existence of non-glycosylated peptides make the direct MS analysis of glycopeptides still a challenge. Hence, an efficient enrichment process prior to MS analysis is needed.To solve these problems, various materials or methods including lectin affinity chromatography, 3a boronic acid affinity chromatography, 3b-d hydrazine beads, 3e Ti(IV)-IMAC 3f and hydrophilic interaction chromatography (HILIC) adsorbents 3g have been utilized for the enrichment of glycopeptides/glycoproteins. Among them, the enrichment strategy based on HILIC has gained increasing popularity and a variety of hydrophilic matrices, such as sepharose, cellulose, ZIC-HILIC beads and click saccharides, have been developed for the selective extraction of glycopeptides. 4 And it was demonstrated that HILIC beads with a high amount of maltose bonded could further improve the profound significance with high selectivity. 5 In recent years, Fe 3 O 4 nanoparticle (MNP) based magnetic separation has become an effective isolation technique, which could achieve better separation compared with conventional approaches, and has attracted much attention in drug delivery, cell separation, bio-separation and enrichment in the biomedical field. 6 Combining the magnetic nano-material with covalently bonded hydrophilic functional molecules could simultaneously achieve the simple and efficient separation of the glycopeptides from the complex peptide mixtures by using magnetic separation. 5,7 Yeh et al. prepared MNPs modified with a hydrophilic polymer by employing spontaneous acid-catalyzed polymerization of zwitterionic monomers, which could be applied for the enrichment of glycopeptides with high selectivity. 7a Recently, a surface initiated atom transfer radical polymerization (SI-ATRP) technique was adopted to obtain the branched PEG brushes hybrid MNPs and then the reactive hydroxyl groups were modified with maltose, which could remarkably increase the amount of immobilized maltose compared to monolayer nanoparticles, and could provide high selectivity and sensitivity for glycopeptide detection. 5...