Glutathione functionalized magnetic covalent organic frameworks with dual-hydrophilicity for highly efficient and selective enrichment of glycopeptides

Abstract

Glycoproteins can be used as biomarkers to detect many diseases. Reliable and efficient sample materials are essential to separate and enrich glycopeptides before detection and analysis. In this report, glutathione (GSH)-modified magnetic covalent organic framework (TpBD) composite Fe3O4@TpBD@Au@GSH was synthesized by a two-step, post-synthesis modification strategy. The native hydrophilic TpBD and the highly hydrophilic GSH furnished the composite with dual-hydrophilic performance that was superior to covalent organic framework-based materials reported previously. The composite material showed excellent performance in enriching glycopeptides from protein standards because of its superior hydrophilicity, with 21 and 36 glycopeptides enriched from horseradish peroxidase (HRP) and immunoglobulin G from human serum (IgG) tryptic digests, respectively. The prepared composite exhibited ultra-high sensitivity (0.1 fmol/µL), excellent selectivity (HRP tryptic digest/bovine serum albumin (BSA) tryptic digest = 1:2000) and macromolecular protein anti-interference ability (HRP tryptic digest/BSA = 1:2000). Moreover, Fe3O4@TpBD@Au@GSH exhibited outstanding binding capacity (160 mg/g), excellent long-term storage capacity and good recycling ability (at least six times). Glycopeptide enrichment of biological samples by Fe3O4@TpBD@Au@GSH was successful, with 492 and 160 glycopeptides, corresponding to 134 and 64 glycoproteins, detected in 5 µL human serum and human saliva samples, respectively. The results showed that Fe3O4@TpBD@Au@GSH provides more information to facilitate in-depth analysis of glycopeptides in biological samples and has broad potential in cancer monitoring and diagnosis.