Design and fabrication of highly hydrophilic magnetic material by anchoring l-cysteine onto chitosan for efficient enrichment of glycopeptides

Hydrophilic interaction liquid chromatography (HILIC) has been recognized as an effective strategy for glycopeptide enrichment. Hydrophilic materials pave the way to solve the limit of low enrichment capacity and poor selectivity. The present study is the first attempt to combine chitosan (CS) and l-cysteine (l-Cys) to design a novel hydrophilic material focusing on glycopeptide enrichment. CS containing a large number of hydrophilic amino and hydroxyl groups has unique chemical properties, which makes it a very attractive biomaterial for glycopeptide enrichment. The excellent hydrophilicity of zwitterionic molecule l-Cys inspires the idea of anchoring l-Cys onto CS to design a novel hydrophilic material (named as Fe3O4@[email protected]l-Cys) for the capture of low abundance glycopeptides. To be specific, Au nanoparticles (Au NPs) was introduced into CS-coated Fe3O4 via electrostatic interaction and served as bridges to anchor l-Cys onto the surface of CS through strong Au-S bond interaction. The prepared Fe3O4@[email protected]l-Cys exhibited strong affinity, low detection limit (0.5 fmol/µL HRP), high selectivity (HRP/BSA with a molar ratio of 1:1000) for glycopeptides. Moreover, successful application of glycopeptide enrichment in human serum and saliva by Fe3O4@[email protected]l-Cys was achieved. A satisfactory data set indicates that Fe3O4@[email protected]l-Cys has promising potential in the application of glycopeptide enrichment in real complex bio-samples and for related glycoproteome research.