title: Metal-assisted polyatomic SIMS and laser desorption/ionization for enhanced small molecule imaging of bacterial biofilms.
abstract: Mass spectrometry imaging (MSI) has become an important analytical tool for many sectors of science and medicine. As the application of MSI expands into new areas of inquiry, existing methodologies must be adapted and improved to meet emerging challenges. Particularly salient is the need for small molecule imaging methods that are compatible with complex multicomponent systems, a challenge that is amplified by the effects of analyte migration and matrix interference. With a focus on microbial biofilms from the opportunistic pathogen Pseudomonas aeruginosa, the relative advantages of two established microprobe-based MSI techniques-polyatomic secondary ion mass spectrometry (SIMS) and laser desorption/ionization-are compared, with emphasis on exploring the effect of surface metallization on small molecule imaging. A combination of qualitative image comparison and multivariate statistical analysis demonstrates that sputtering microbial biofilms with a 2.5 nm layer of gold selectively enhances C60-SIMS ionization for several molecular classes including rhamnolipids and 2-alkyl-quinolones. Metallization also leads to the reduction of in-source fragmentation and subsequent ionization of media-specific background polymers, which improves spectral purity and image quality. These findings show that the influence of metallization upon ionization is strongly dependent on both the surface architecture and the analyte class, and further demonstrate that metal-assisted C60-SIMS is a viable method for small molecule imaging of intact molecular ions in complex biological systems.
authors.affiliation: Department of Chemistry and Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801.
authors.forename: Sage J B
authors.initials: SJ
authors.lastname: Dunham
authors.affiliation: Department of Chemistry and Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801.
authors.forename: Troy J
authors.initials: TJ
authors.lastname: Comi
authors.affiliation: Department of Chemistry and Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801.
authors.forename: Kyungwon
authors.initials: K
authors.lastname: Ko
authors.affiliation: Department of Chemistry and Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801.
authors.forename: Bin
authors.initials: B
authors.lastname: Li
authors.affiliation: Department of Chemistry and Biochemistry and Department of Chemical and Biomolecular Engineering, University of Notre Dame, Notre Dame, Indiana 46556.
authors.forename: Nameera F
authors.initials: NF
authors.lastname: Baig
authors.affiliation: Department of Civil and Environmental Engineering and Earth Sciences and Department of Biological Sciences, University of Notre Dame, Notre Dame, Indiana 46556 and Eck Institute for Global Health, University of Notre Dame, Notre Dame, Indiana 46556.
authors.forename: Nydia
authors.initials: N
authors.lastname: Morales-Soto
authors.affiliation: Department of Civil and Environmental Engineering and Earth Sciences and Department of Biological Sciences, University of Notre Dame, Notre Dame, Indiana 46556 and Eck Institute for Global Health, University of Notre Dame, Notre Dame, Indiana 46556.
authors.forename: Joshua D
authors.initials: JD
authors.lastname: Shrout
authors.affiliation: Department of Chemistry and Biochemistry and Department of Chemical and Biomolecular Engineering, University of Notre Dame, Notre Dame, Indiana 46556.
authors.forename: Paul W
authors.initials: PW
authors.lastname: Bohn
authors.affiliation: Department of Chemistry and Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801.
authors.forename: Jonathan V
authors.initials: JV
authors.lastname: Sweedler
mesh_terms: D018441:Biofilms; D008670:Metals / Q000378:metabolism*; D061848:Optical Imaging / Q000379:methods*; D011550:Pseudomonas aeruginosa / Q000737:chemistry* / Q000502:physiology*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods*; D018629:Spectrometry, Mass, Secondary Ion / Q000379:methods*
chemical_list: D008670:Metals