Preparation of titanium-grafted magnetic mesoporous silica for the enrichment of endogenous serum phosphopeptides

As one of the most important post-translational modifications, reversible phosphorylation of protein plays crucial roles in a large number of biological processes. Moreover, endogenous phosphopeptides are also associated with certain human diseases. An efficient enrichment and separation method is the premise for successful identification and quantification of phosphopeptides. In this work, titanium grafted magnetic mesoporous silica (Fe 3 O 4 @Ti-mSiO 2 ) was developed and applied for the enrichment of endogenous phosphopeptides. Fe 3 O 4 @Ti-mSiO 2 particles were prepared by grafting titanocene dichloride on the inner walls of magnetic mesoporous silica and then being calcined to remove cyclopentadienyl ligand. The physicochemical properties of the prepared materials were characterized by energy dispersive X-ray spectroscopy (EDX), nitrogen adsorption–desorption analysis, X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and vibrating sample magnetometer (VSM). For selective enrichment of phosphopeptides, the prepared Fe 3 O 4 @Ti-mSiO 2 particles were applied for tryptic digests of β -casein, mixtures of β -casein and bovine serum albumin (BSA), and low-fat milk. Finally, Fe 3 O 4 @Ti-mSiO 2 was successfully applied for the enrichment of endogenous phosphopeptides from human serum.