title: Enhanced signal intensity in matrix-free laser desorption ionization mass spectrometry by chemical modification of bionanostructures from diatom cell walls.
abstract: BACKGROUND
  Laser desorption ionization for mass spectrometric measurements (LDI MS) is supported by nanostructured materials. This technique helps to overcome known limitations of matrix-assisted laser desorption/ionization (MALDI) and especially avoids interfering signals caused by matrix components. LDI can be supported by bionanostructures from the cell walls of diatoms. We explore how ionization efficiency can be improved by chemical modification of the cell walls.
  
  
  METHODS
  We introduce procedures to chemically modify these nanopatterned silicate structures using perfluorooctyldimethylchlorosilane or pentafluorophenylpropyldimethylchlorosilane. Using a conventional MALDI-MS instrument we compare ionization using the novel materials with that of unmodified cell walls. The functionalized bionanomaterial is comprehensively evaluated for the use in LDI MS using a broad range of analytes and two commercial drugs.
  
  
  RESULTS
  Chemical modifications lead to materials that support LDI significantly better than unmodified diatom cell walls. LDI signal intensity was up to 25-fold increased using the modified preparations. No interfering signals in the lower molecular weight range down to m/z 100 were observed, demonstrating the suitability of the method for small analytes. Crude solutions of commercial drugs, such as Aspirin complex(®) and IbuHEXAL(®) could be directly investigated without additional sample preparation.
  
  
  CONCLUSIONS
  Chemically modified diatom cell walls represent a powerful tool to support ionization in LDI MS. The lack of background signals in the low molecular weight region of the mass spectra allows also the investigations of small analytes.
authors.affiliation: Institute for Inorganic and Analytical Chemistry, Friedrich Schiller University Jena, Lessingstraße 8, 07743, Jena, Germany.
authors.forename: Tino
authors.initials: T
authors.lastname: Jaschinski
authors.forename: Kathleen
authors.initials: K
authors.lastname: Thume
authors.forename: Moritz
authors.initials: M
authors.lastname: Klein
authors.forename: Phillipp
authors.initials: P
authors.lastname: Richter
authors.forename: Jürgen
authors.initials: J
authors.lastname: Popp
authors.forename: Aleš
authors.initials: A
authors.lastname: Svatoš
authors.forename: Georg
authors.initials: G
authors.lastname: Pohnert
mesh_terms: D002473:Cell Wall / Q000737:chemistry* / Q000648:ultrastructure*; D017377:Diatoms / Q000737:chemistry*; D008956:Models, Chemical; D017640:Silicates / Q000737:chemistry; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods*
chemical_list: D017640:Silicates