Surface-assisted laser desorption–ionization mass spectrometry on titanium dioxide (TiO2) nanotube layers

Abstract

The paper reports on the use of a titanium oxide (TiO₂) nanotube layer as a sensitive substrate for surface-assisted laser desorption–ionization mass spectrometry (SALDI-MS) of peptides and small molecules. The nanotube layers were prepared by electrochemical anodization of titanium foil. The optimized TiO₂ nanotubes morphology coupled to a controlled surface chemistry allowed desorption–ionization (D/I) of a peptide mixture (Mix1) with a detection limit of 10 femtomoles for the neurotensin peptide. The performance of the TiO₂ nanotubes for the D/I of small molecules was also tested for the detection of sutent, a small tyrosine kinase inhibitor, and verapamil. A detection limit of 50 fmol was obtained for these molecules, as compared to 500 fmol using classical matrix-assisted laser desorption–ionization mass spectrometry (MALDI-MS). Both amorphous and anatase TiO₂ layers displayed a comparable performance for D/I of analyte molecules. In a control experiment, we have performed D/I of analyte molecules on a flat TiO₂ layer. The absence of signal emphasizes the role of the nanostructured substrate in the D/I process.