title: Ambient imaging mass spectrometry by electrospray ionization using solid needle as sampling probe.
abstract: Although being an atmospheric pressure ion source, electrospray ionization (ESI) has rarely been used directly for ambient imaging mass spectrometry because the sample has to be introduced as liquid solution through the capillary. Instead of capillary, probe electrospray ionization (PESI), which has been developed recently, uses a solid needle as the sampling probe, as well as the electrospray emitter, and has been applied not only for liquid solutions but also for the direct sampling on wet samples. Biological tissues are composed of cells that contain 70-90% water, and when the surface is probed by the needle tip, the biological fluid adhering to the needle can be electrosprayed directly or assisted by additional solvent added onto the needle surface. Here, we demonstrate ambient imaging mass spectrometry of mouse brain section using PESI, incorporated with an auxiliary heated capillary sprayer. The solvent vapor generated from the sprayer condensed on the needle tip, re-dissolving the adhered sample, and at the same time, providing an indirect means for needle cleaning. The histological sections were prepared by fixation using paraformaldehyde, and the spatial analysis was automated by maintaining an equal sampling depth into the sample in addition to raster scan. Phospholipids and galactosylceramides were readily detected from the mouse brain section in the positive ion mode, and were mapped with 60 microm lateral resolution to form mass spectrometric images.
authors.affiliation: Clean Energy Research Center, University of Yamanashi, Takeda 4-3-11, Kofu, 400-8511, Japan. leechuin.yamanashi@gmail.com
authors.forename: Lee Chuin
authors.initials: LC
authors.lastname: Chen
authors.forename: Kentaro
authors.initials: K
authors.lastname: Yoshimura
authors.forename: Zhan
authors.initials: Z
authors.lastname: Yu
authors.forename: Rikiya
authors.initials: R
authors.lastname: Iwata
authors.forename: Hajime
authors.initials: H
authors.lastname: Ito
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Suzuki
authors.forename: Kunihiko
authors.initials: K
authors.lastname: Mori
authors.forename: Osamu
authors.initials: O
authors.lastname: Ariyada
authors.forename: Sen
authors.initials: S
authors.lastname: Takeda
authors.forename: Takeo
authors.initials: T
authors.lastname: Kubota
authors.forename: Kenzo
authors.initials: K
authors.lastname: Hiraoka
mesh_terms: D000818:Animals; D001921:Brain; D001923:Brain Chemistry; D006358:Hot Temperature; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009339:Needles; D012160:Retina / Q000737:chemistry; D021241:Spectrometry, Mass, Electrospray Ionization / Q000295:instrumentation* / Q000379:methods; D013552:Swine; D014835:Volatilization