Facile fabrication of hydrophilic covalent organic framework composites for highly selective enrichment of N-glycopeptides.

The development of facilely synthetic materials acts an essential role in glycoproteome analysis, especially for the highly efficient enrichment of N-linked glycopeptides. In this work, a facile and timesaving route was introduced in which COF served as a carrier and poly (ethylenimine) (PEI) and carrageenan (Carr) were successively coated on the surface via electrostatic interaction. The resultant COF@PEI@Carr showed remarkable performance in glycopeptide enrichment with high sensitivity (2 fmol μL), high selectivity (1:800, molar ratio of human serum IgG to BSA digests), large loading capacity (300 mg g), satisfactory recovery (102.4 ± 6.0%) and reusability (at least eight times). Due to the brilliant hydrophilicity and electrostatic interactions between COF@PEI@Carr and positively charged glycopeptides, the prepared materials could be applied in the identification and analysis in the human plasma of healthy subjects and patients with nasopharyngeal carcinoma. As a result, 113 N-glycopeptides with 141 glycosylation sites corresponding to 59 proteins and 144 N-glycopeptides with 177 glycosylation sites corresponding to 67 proteins were enriched from 2 μL plasma trypsin digests of the control groups and patients with nasopharyngeal carcinoma, respectively. 22 glycopeptides were identified only from the normal controls and 53 glycopeptides were detected only from the other set. The results demonstrated that this hydrophilic material was promising on a large scale and further N-glycoproteome research.