Time-of-flight secondary ion mass spectrometry (TOF-SIMS) is an established, highly sensitive analytical technique for mass spectrometry (MS) imaging applications with a lateral resolution below 100 nm. Application of this technique for the localization of drugs and their metabolites in drug-doped cells could be used to find regions in which a pharmaceutical compound accumulates. This information would be extremely helpful for selection of possible drug candidates in pre-clinical studies, thereby reducing the development costs for new pharmaceutical products. Furthermore, surveying biologically relevant molecules, such as lipids, in tissue can give valuable information on the molecular fundamentals of diseases and the effects of treatments.

However, in complex biological samples identification of unknown compounds can be hampered by mass interferences and a high number of possible assignments for a single mass peak. In order to overcome these limitations, the 3D nanoSIMS project [1] is developing a revolutionary new SIMS instrument that combines the high lateral resolution and speed associated with TOF-SIMS (TOF.SIMS 5, ION-TOF GmbH, Muenster, Germany) with the high mass resolution and high mass accuracy of an orbital trapping mass analyzer (QExactive^TM HF [2], Thermo Fisher Scientific^TM, Bremen, Germany). The instrument is equipped with a newly developed gas cluster ion beam column which provides the capability to image with a lateral resolution down to the micron level with minimum sub-surface damage. In this contribution we will report about results obtained from different biological application areas such as tissue imaging, lipidomics, and single cell analysis. From coronal mouse brain tissue slices, we fully separate the (3'-sulfo)Gal-Cer(d18:1/24:1(2-OH)) and (3'-sulfo)Gal-Cer(d18:1/25:0) sulfatides, which reveals a difference in spatial distribution. In the low mass region, mass resolving powers of >400,000 are achieved allowing clear separation of the low abundance metabolite dopamine from other peaks, which has not been possible before.

Analyzing NR8383 cells, we show the ability to image the drug amiodarone with sub-cellular resolution and show that the mass spectra are not affected by sample topography.

Furthermore the MS/MS capability of the QExactive Instrument is used to confirm proposed assignments on tissue and from single cells.

[1] The 3D nanoSIMS project, http://www.npl.co.uk/news/3d-nanosims-label-free-molecular-imaging

[2] Scheltema, et al. Mol Cell Proteomics (2014).