Synthesis of porous TiO₂/SiO₂ monodisperse hollow spheres as a platform for phosphopeptide enrichment

A uniform dispersion of TiO₂/SiO₂ hollow nanosphere of 290 nm with a high surface area of more than 100 m²g^{− 1} is prepared using polystyrene spheres as templates after calcination at 600 °C. The TiO₂/SiO₂ hollow nanospheres are characterized by scanning electron microscopy, transmission electron microscopy, dynamic light scattering, nitrogen adsorption-desorption isotherms, and X-ray diffraction. The TiO₂/SiO₂ hollow nanospheres are shown to be highly effective in selectively enriching phosphopeptides, resulting in a significant reduction of non-phosphorylated species and an enhanced presence of modified peptides. The favorable results obtained in the present study for the enrichment of phosphoprotein β-casein pave the way toward a similar treatment of other types of biomolecules.