title: TOF-SIMS 3D biomolecular imaging of Xenopus laevis oocytes using buckminsterfullerene (C60) primary ions.
abstract: Time-of-flight secondary ion mass spectrometry (TOF-SIMS) using buckminsterfullerene (C60) as the primary ion source has the ability to generate chemical images of surfaces with high sensitivities and minimal chemical damage. We studied the application of C60+ to depth profile a biological cell surface in a controlled manner and to subsequently image the revealed subsurfaces, in order to generate three-dimensional molecular images of the biological system. Such an analytical tool not only enables the surface localization of molecular species to be mapped but also enables the biomolecular distribution as a function of depth to be investigated with minimal sample preparation/intervention. Here we demonstrate the technique with a freeze-dried Xenopus laevis oocyte, which is a single cell. A C60+ ion beam was used with computer-controlled analyses and etch cycles. Mass spectra derived from the surface revealed peaks corresponding to cholesterol (m/z 369) and other lipids at m/z 540-570 and 800-1000, in the positive ion mode, and lipid fatty acid side chains (e.g., m/z 255) in the negative ion mode. To our knowledge, this is the first demonstration of the 3D biomolecular imaging within an actual biological system using TOF-SIMS.
authors.affiliation: Manchester Interdisciplinary Biocentre, Centre for Instrumentation and Analytical Science, School of Chemical Engineering and Analytical Science, The University of Manchester, Manchester, M1 7ND, UK. John.Fletcher@ manchester.ac.uk
authors.forename: John S
authors.initials: JS
authors.lastname: Fletcher
authors.forename: Nicholas P
authors.initials: NP
authors.lastname: Lockyer
authors.forename: Seetharaman
authors.initials: S
authors.lastname: Vaidyanathan
authors.forename: John C
authors.initials: JC
authors.lastname: Vickerman
mesh_terms: D000818:Animals; D037741:Fullerenes / Q000737:chemistry*; D021621:Imaging, Three-Dimensional / Q000379:methods*; D007477:Ions / Q000737:chemistry; D009865:Oocytes / Q000737:chemistry*; D018629:Spectrometry, Mass, Secondary Ion / Q000379:methods*; D014982:Xenopus laevis
chemical_list: D037741:Fullerenes; D007477:Ions