Super-hydrophilic sulfonate-modified covalent organic framework nanosheets for efficient separation and enrichment of glycopeptides

Highly efficient extraction of glycopeptides prior to mass spectrometry detection is extremely crucial for glycoproteomic research, especially in disease biomarker research. Reported here is the first time by applying two-dimensional (2D) covalent organic framework (COFs) nanosheets for highly efficient enrichment of glycopeptides. Particularly, by incorporating hydrophilic monomers through a bottom-up strategy, the 2D COF nanosheets (denoted as NUS-9) displayed an ultra-high graft density of sulfonic groups and super-hydrophilicity. In addition, because of the large surface area, low steric hindrance, high chemical stability, and abundant accessibility sites of 2D COF nanosheets, NUS-9 exhibited remarkable efficiency for glycopeptide enrichment, involving excellent detection sensitivity (0.01 fmol μL), outstanding enrichment capability, and good enrichment selectivity (1:1500, horseradish peroxidase (HRP) tryptic digest to bovine serum albumin (BSA) tryptic digest), and recovery (92.2 ± 2.0%). Moreover, the NUS-9 was able to unambiguously detect 631 endogenous glycopeptides from human saliva, demonstrating an unparalleled high efficiency in glycopeptide enrichment. Gene ontology analyses of proteins from human saliva enriched by NUS-9 demonstrated its potential for comprehensive glycoproteome analysis.