Ti⁴⁺ functionalized β-cyclodextrin covalent organic framework as a new immobilized metal ion affinity chromatography...

A Ti⁴⁺ functionalized β-cyclodextrin covalent organic framework nanoparticle (named as β-CD-COF@Ti⁴⁺) was synthesized using a one-pot method successfully realizing the enrichment of phosphorylated peptides and exosomes based on the immobilized metal ion affinity chromatography strategy. The functionalized β-CD-COF@Ti⁴⁺ exhibited superior performance on the enrichment of phosphopeptides, including high selectivity (1:1000), low detection limit (0.5 fmol), and loading capacity for phosphopeptides (100 mg·g^-1). After treatment with β-CD-COF@Ti⁴⁺, 9 phosphopeptides from defatted milk, 29 phosphopeptides related to 23 phosphoproteins from normal group serum, and 24 phosphopeptides related to 22 phosphoproteins from the serum of uremia patients were captured. Through the analysis of Gene Ontology, the captured phosphoprotein is closely related to kidney disease, including lipoprotein metabolism, very-low-density lipoprotein particle, high-density lipoprotein particle, and lipid binding activity process. Furthermore, western blot verification showed that this nanoparticle could successfully capture exosomes from human serum. This study demonstrates great prospects for the enrichment of phosphopeptides and exosomes from actual bio-samples.