Facile synthesis of titania nanoparticles coated carbon nanotubes for selective enrichment of phosphopeptides for mass spectrometry analysis

In this work, titania nanoparticles coated carbon nanotubes (denoted as CNTs/TiO2 composites) were synthesized through a facile but effective solvothermal reaction using titanium isopropoxide as the titania source, isopropyl alcohol as the solvent and as the basic catalyst in the presence of hydrophilic carbon nanotubes. Characterizations using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) indicate that the CNTs/TiO2 composites consist of CNT core and a rough outer layer formed by titania nanoparticles (5–10 nm). Measurements using wide angle X-ray diffraction (WAXRD), zeta potential and N2 sorption reveal that the titania shell is formed by anatase titania nanoparticles, and the composites have a high specific surface area of about 104 m2/g. By using their high surface area and affinity to phosphopeptides, the CNTs/TiO2 composites were applied to selectively enrich phosphopeptides for mass spectrometry analysis. The high selectivity and capacity of the CNTs/TiO2 composites have been demonstrated by effective enrichment of phosphopeptides from digests of phosphoprotein, protein mixtures of β-casein and bovine serum albumin, human serum and rat brain samples. These results foresee a promising application of the novel CNTs/TiO2 composites in the selective enrichment of phosphopeptides.