Hydrophilic phytic acid-functionalized magnetic dendritic mesoporous silica nanospheres with immobilized Ti4+: A dual-purpose affinity material for highly efficient enrichment of glycopeptides/phosphopeptides

In this work, magnetic mesoporous silica microspheres (Mag-MSMs) with ordered radial mesochannels were fabricated by a self-assembly synthesis in chlorobenzene-water mixed system. Then, the obtained Mag-MSMs were modified with polyethyleneimine (PEI), phytic acid (PA) and Ti4+ (denoted as Mag-MSMs@PEI-PA-Ti4+) via layer by layer (LbL) assembly. Due to the excellent hydrophilicity of PEI and PA and the large amount of Ti4+, the Mag-MSMs@PEI-PA-Ti4+ possessed combined properties of hydrophilic interaction liquid chromatography (HILIC)- and immobilized metal ion affinity chromatography (IMAC)-based materials, which could be used as a dual-purpose material for N-glycopeptides or phosphopeptides enrichment. The proposed Mag-MSMs@PEI-PA-Ti4+ exhibited an outstanding performance for N-glycopeptides enrichment (selectivity: IgG/BSA = 1:1000; sensitivity: 0.5 fmol/mu L. IgG) and phosphopeptides enrichment (selectivity: alpha-casein/BSA = 1:5000; sensitivity: 0.2 fmol/mu L alpha-casein). Furthermore, after enrichment with Mag-MSMs@PEI-PA-Ti4+, a total of 276 N-glycopeptides assigned to 132 glycoproteins were identified from 2 mu L human serum and 1645 phosphopeptides corresponding to 704 phosphoproteins were identified from 200 mu g HeLa cell extracts.