Magnetic mesoporous silica nanoparticles modified by phosphonate functionalized ionic liquid for selective enrichment of phosphopeptides

In this study, new magnetic nanoparticles (denotated as Fe(3)O(4)@mSiO(2)-PFIL-Ti(4+)) have been prepared by immobilizing titanium ions with phosphonate functionalized ionic liquid (PFIL) on the wall of core–shell structured mesoporous nanomaterials. The resulting nanoparticles possess large specific surface area, strong hydrophilicity and fast magnetic response. The composites can capture traces of phosphopeptides from the tryptic β-casein digest (0.08 fmol), a digest mixture of β-casein and BSA (1 : 10 000, molar ratio) as well as a blend of β-casein digest and a great quantity of phosphorylated protein (β-casein) and non-phosphorylated protein (BSA) (1 : 2000 : 2000, mass ratio), respectively, showing excellent sensitivity, selectivity and size exclusion ability. Additionally, Fe(3)O(4)@mSiO(2)-PFIL-Ti(4+) shows excellent steadiness and can be reused at least 12 times. Moreover, this material was successfully applied to enrich endogenous phosphopeptides from complex bio-samples, including human saliva and serum.