Boronic acid functionalized MOFs as HILIC material for N-linked glycopeptide enrichment

Highly specific enrichment of N-linked glycopeptides from complex biological samples is crucial prior to mass spectrometric analysis. In this work, a hydrophilic metal-organic framework composite is prepared by the growth of UiO-66-NH₂ on graphene sheets, followed by its post-synthetic modification to attach boronic acid to form GO@UiO-66-PBA. The fabrication of graphene oxide-MOF composite results in enhanced surface area with improved thermal and chemical stability. The synthesized MOF nanocomposite is characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and BET. A crystalline structure with high porosity offering large surface area and good hydrophilicity of the nanocomposite assists as an enrichment tool in glycoproteomics. The GO@UiO-66-PBA nanocomposite selectively enriches N-linked glycopeptides from tryptic digests of horseradish peroxidase (HRP) and immunoglobulin (IgG). GO@UiO-66-PBA nanoparticles show a low detection limit (1 fmol) and good specificity (1:200), reusability and reproducibility for N-linked glycopeptide enrichment from IgG digest. The binding capacity of GO@UiO-66-PBA is 84 mg/g for protein concentration, with a good recovery of 86.5%. A total of 372 N-linked glycopeptides corresponding to different glycoproteins are identified from only 1 μL of human serum digest. Thus, the presented research work can be an efficient separation platform for N-linked glycopeptide enrichment from complex samples, which can be extended to cost-effective routine analysis. Graphical abstract.