title: Remote laser ablation electrospray ionization mass spectrometry for non-proximate analysis of biological tissues.
abstract: BACKGROUND
  We introduce remote laser ablation electrospray ionization (LAESI), a novel, non-proximate ambient sampling technique. Remote LAESI allows additional analytical instrumentation to be incorporated during sample analysis. This work demonstrates the utility of remote LAESI and, when combined with optical microscopy, allows for the microscopy-guided sampling of biological tissues.
  
  
  METHODS
  Rapid prototyping using a 3D printer was applied to produce various ablation chamber geometries. A focused 5 ns, 2.94 µm laser pulse kept at 10 Hz ablated the sample within the chamber, remote to the mass spectrometer inlet. Ablated particulates were carried through a transfer tube by N2 gas, delivered to the electrospray plume and ionized. A long-distance microscope was used to capture images of tissues before, during and after ablation.
  
  
  RESULTS
  Optimized remote LAESI was found to have a 27% transport efficiency compared with conventional LAESI, sufficient for many applications. A comparable molecular coverage was obtained with remote LAESI for the analysis of plant tissue. Proof-of-principle experiments using a pansy flower and a maple leaf indicated the functionality of this approach for selecting domains of interest for analysis by optical microscopy and obtaining chemical information from those selected regions by remote LAESI-MS.
  
  
  CONCLUSIONS
  Remote LAESI is an ambient non-proximate sampling technique, proven to detect metabolites in biological tissues. When combined with optical microscopy, remote LAESI allows for the simultaneous acquisition of morphological and chemical information. This technique has important implications for histology, where chemical information for specific locations within a tissue is critical.
authors.affiliation: Department of Chemistry, W.M. Keck Institute for Proteomics Technology and Applications, The George Washington University, Washington, DC, 20052, USA.
authors.forename: Laine R
authors.initials: LR
authors.lastname: Compton
authors.forename: Brent
authors.initials: B
authors.lastname: Reschke
authors.forename: Jordan
authors.initials: J
authors.lastname: Friend
authors.forename: Matthew
authors.initials: M
authors.lastname: Powell
authors.forename: Akos
authors.initials: A
authors.lastname: Vertes
mesh_terms: D004867:Equipment Design; D035264:Flowers / Q000737:chemistry; D007834:Lasers; D008954:Models, Biological; D057054:Molecular Imaging / Q000379:methods*; D018515:Plant Leaves / Q000737:chemistry; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods; D014700:Verapamil / Q000737:chemistry; D032413:Viola / Q000737:chemistry
chemical_list: D014700:Verapamil