Post-synthesis of covalent organic frameworks with dual-hydrophilic groups for specific capture of serum exosomes

Exosomes can reflect the physiological state of parent cells and are potential disease biomarkers. In this study, we developed an innovative hydrophilic material by post-synthesis of covalent organic frameworks with dual hydrophilic groups of glutathione and cysteine (denoted as COF-S@Au@GC) to detect glycosylated exosomes in human serum. COF-S@Au@GC enriched glycosylated exosomes in human serum due to glutathione and cysteine (GC) hydrophilicity. Our results show that COF-S@Au@GC has a detection limit of 5 amol μL^-1, selectivity of 1:2000, size-exclusion effect of 1:10,000, repeatability of 10 cycles, recovery of 98.3 ± 0.5%, and loading capacity of 50 mg g^-1 for glycopeptides. In addition, 182 glycopeptides were detected after enrichment with COF-S@Au@GC from renal carcinoma serum, demonstrating the feasibility of enriching glycopeptides from complex biological samples. Furthermore, COF-S@Au@GC successfully captured glycosylated exosomes in the serum of renal cancer patients, with their 161 glycopeptides detected by nano liquid chromatography with tandem mass spectrometry (LC-MS/MS). This study provides a new heuristic strategy for isolating exosomes and contributes to further functional analysis of exosomes.