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.