Preparation Of Hydrophilic Functionalized Magnetic Materials And Applications In Glycopeptide Analysis

Protein is the principal undertaker of human life activities and the most direct implementor of biological functions.Glycosylation is considered as one of the most important and widely studied post-translational modifications.Mass spectrometry(MS)has played an important role in the analysis of glycoproteins/glycopeptides.However,low abundance of glycoperteins and interference caused by many non-glycopeptides make direct detection of glycoproteins/glycopeptides difficult in MS measurement.Therefore,a series of affinity methods for glycopeptides have been developed,including lectin affinity chromatography,hydrazide chemistry,boronic acid affinity chromatography,and hydrophilic interaction liquid chromatography(HILIC).Based on HILIC strategy,many hydrophilic functionalized materials have been developed for selective enrichment of glycopeptides,which paves the way to solve the limitation of poor enrichment performance and selectivity.At present,hydrophilic functionalized materials generally include graphene oxide-,metal-organic frameworks-,covalent organic frameworks-,monolithic columns-,magnetic nanoparticles-based hydrophilic materials and so on.Magnetic nanomaterials have been extensively studied in the field of separation and enrichment.Due to their paramagnetism,magnetic materials as adsorbents make the subsequent analysis easier and more convenient.More importantly,the surface of magnetic nanoparticles is easy to modify,which can be functionalized to obtain new functionalized magnetic materials.A lot of hydrophilic functionalized magnetic materials have been developed.The surface of magnetic nanoparticles is functionalized with hydrophilic substances to prepare materials with high hydrophilicity.The obtained materials show high capacity and high selectivity for glycopeptide enrichment.Combined with bio-mass spectrometry,hydrophilic magnetic functionalized materials have a broad application prospect in the analysis of low abundance glycopeptides from complex biological samples.The specific experimental content consists of the following two parts:1.A novel hydrophilic material was designed by combining chitosan(CS)and L-cysteine(L-Cys).CS containing a large number of hydrophilic amino and hydroxyl groups is a very attractive biomaterial for glycopeptide enrichment.L-Cys,a zwitterionic molecule,also has excellent hydrophilicity.Anchoring L-Cys onto CS to design a hydrophilic magnetic functionalized material(named as Fe₃O₄@CS@Au-L-Cys)is applied to the capture of low abundance glycopeptides.To be specific,gold nanoparticles(Au NPs)were attached to the surface of CS-coated Fe₃O₄ by electrostatic interaction,and then L-Cys was anchored onto the CS through strong Au-S bonding.Combined with MALDI-TOF MS,the hydrophilic material has high sensitivity,high selectivity and good reusability for glycopeptide enrichment,and has been successfully applied to the enrichment of glycopeptides from real complex biological samples.2.The?-cyclodextrin(?-CD)crosslinked polymer,containing a large number of?-CD units,was synthesized with epichlorohydrin(EPI)as crosslinker.Afterwards,?-CD polymer-modified magnetic material possessing numerous hydrophilic groups and?-CD cavities was prepared by one-pot method.The hydrophilic molecule mercaptosuccinic acid(MSA)was introduced into the surface of magnetic?-CD polymer by host-guest interactions between?-CD and adamantane(Ada)to improve the hydrophilicity of the material and thus enhance the enrichment performance toward glycopeptides.The high hydrophilicity of this magnetic material is contributed to the hydrophilicity of many hydroxyl groups in?-CD polymer and carboxyl groups in MSA.In addition,the paramagnetism of the material is conducive to the realization of rapid pretreatment.Combined with MALDI-TOF MS method,high sensitivity(detection limit of 0.1 fmol?L^-1)for glycopeptide enrichemnt was achieved.The approach has been successfully applied to the enrichment of glycopeptides from human serum and saliva.