title: Colloidal TiO2 nanoparticles as substrates for M(S)ALDI mass spectrometry of transition metal complexes.
abstract: BACKGROUND
  Nanoparticles as substrates for matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) have advantages over organic matrices, since they enable acquisition of spectra in the low-mass range. It has been previously shown that TiO(2) nanoparticles can be used as substrate for MALDI-TOF MS analysis of phospholipids and for other types of molecules, but none of them was applied to the analysis of transition metal complexes.
  
  
  METHODS
  The MALDI-TOF mass spectra of potential anti-tumor drugs [AuCl(2)(bipy)]Cl, [PtCl(4)(bipy)], and [RuCl(2)(bipy)(2) ]Cl acquired with organic matrices have been compared with spectra acquired with colloidal titanium dioxide nanoparticles. Colloidal TiO(2) nanoparticles (NPs) with average diameter of 5 nm were synthesized and characterized by microscopy. For some experiments, the TiO(2) NPs were treated at 60 °C. Suspensions of matrix and the analyte were premixed, applied to the MALDI target and left at room temperature. Mass spectra were acquired with a 50-Hz pulsed nitrogen laser emitting at a wavelength of 337 nm.
  
  
  RESULTS
  The MALDI spectra of transition metal complexes acquired with TiO(2) NPs exhibited somewhat lower sensitivity than those with organic matrices; on the other hand, they are characterized by significantly lower number of signals arising from the tested complexes than the organic matrices. Whereas adducts between organic matrices and the analytes were detectable in the spectra, this was not the case for the TiO(2)-assisted mass spectra.
  
  
  CONCLUSIONS
  We have shown that colloidal TiO(2) NPs can be used as substrates for MALDI-TOF MS of transition metal complexes. Although the sensitivity of this approach in comparison with the use of organic matrices might still be a problem, the potential of the applications of NPs for the mass spectrometric characterization of transition metal complexes is clearly demonstrated.
authors: Department of Physical Chemistry, Vinča Institute of Nuclear Sciences, University of Belgrade, Belgrade, Republic of Serbia.
authors: Maja
authors: M
authors: Radisavljević
authors: Tina
authors: T
authors: Kamčeva
authors: Iva
authors: I
authors: Vukićević
authors: Marija
authors: M
authors: Radoičić
authors: Zoran
authors: Z
authors: Šaponjić
authors: Marijana
authors: M
authors: Petković