Chitosan functionalized two-dimensional covalent organic framework nanosheets with high hydrophilicity for efficient glycopeptide enrichment

Glycopeptides are an important biomarker, which play a crucial role in various biological processes. Due to their low abundance and the presence of interfering macromolecular proteins, enrichment of glycopeptides is necessary before testing. However, most materials for enriching glycopeptides have high site resistance, relatively low surface area, and limited recognition sites. Herein, a highly hydrophilic two-dimensional (2-D) covalent organic framework (NUS-10) loaded with chitosan (CS) (denoted as NUS-10@CS) had been synthesized. After enrichment with NUS-10@CS, a total of 34 glycopeptides from horseradish peroxidase (HRP) tryptic digests were detected, demonstrating a high enrichment efficiency for glycopeptides from model glycoprotein digestion. Meanwhile, the material exhibited ultra-high adsorption capacity (1 fmol/μL HRP), excellent selectivity (HRP tryptic digest/bovine serum albumin (BSA) tryptic digest = 1:2000), macromolecular protein anti-interference ability (HRP tryptic digest/BSA = 1:2000) and good binding capacity (200 mg/g). Additionally, 712 glycopeptides corresponding to 200 glycoproteins were identified from 3 µL human serum. NUS-10@CS was promising for glycopeptide analysis, helping to identify potential disease biomarkers more efficiently, and leading to easier and more accurate diagnosis of diseases, which was essential for early intervention and treatment.