Amorphous TiO 2 Nanotubes as a Platform for Highly Selective Phosphopeptide Enrichment.

This work reports highly selective phosphopeptide enrichment using amorphous TiO nanotubes (TiONTs) and the same material decorated with superparamagnetic FeO nanoparticles (TiONTs@FeONPs). TiONTs and TiONTs@FeONPs materials were applied for phosphopeptide enrichment both from a simple peptide mixture (tryptic digest of bovine serum albumin and α-casein) and from a complex peptide mixture (tryptic digest of Jurkat T cell lysate). The obtained enrichment efficiency and selectivity for phosphopeptides of TiONTs and TiONTs@FeONPs were increased to 28.7 and 25.3%, respectively, as compared to those of the well-established TiO microspheres. The enrichment protocol was extended for a second elution step facilitating the identification of additional phosphopeptides. It further turned out that both types of amorphous TiO nanotubes provide qualitatively new physicochemical features that are clearly advantageous for highly selective phosphopeptide enrichment. This has been confirmed experimentally resulting in substantial reduction of non-phosphorylated peptides in the enriched samples. In addition, TiONTs@FeONPs combine high selectivity and ease of handling due to the superparamagnetic character of the material. The presented materials and performances are further promising for applications toward a whole range of other types of biomolecules to be treated in a similar fashion.