During early-stage drug development, drug and metabolite distribution studies are carried out in animal tissues using a range of techniques, particularly whole body autoradiography (WBA). While widely employed, WBA has a number of limitations, including the following: expensive synthesis of radiolabeled drugs and analyte specificity and identification. WBA only images the radiolabel. MALDI MSI has been shown previously to be advantageous for imaging the distribution of a range of drugs and metabolites in whole body sections. Ion mobility separation (IMS) adds a further separation step to imaging experiments; demonstrated here is MALDI-IMS-MS whole body imaging of rats dosed at 6 mg/kg i.v. with an anticancer drug, vinblastine and shown is the distribution of the precursor ion m/z 811.4 and several product ions including m/z 793, 751, 733, 719, 691, 649, 524, and 355. The distribution of vinblastine within the ventricles of the brain is also depicted. Clearly demonstrated in these data are the removal of interfering isobaric ions within the images of m/z 811.4 and also of the transition m/z 811-751, resulting in a higher confidence in the imaging data. Within this work, IMS has shown to be advantageous in both MS and MS/MS imaging experiments by separating vinblastine from an endogenous isobaric lipid.

MALDI imaging mass spectrometry (MALDI-IMS) has become a powerful tool for the detection and localization of drugs, proteins, and lipids on-tissue. Nevertheless, this approach can only perform identification of low mass molecules as lipids, pharmaceuticals, and peptides. In this article, a combination of approaches for the detection and imaging of proteins and their identification directly on-tissue is described after tryptic digestion. Enzymatic digestion protocols for different kinds of tissues-formalin fixed paraffin embedded (FFPE) and frozen tissues-are combined with MALDI-ion mobility mass spectrometry (IM-MS). This combination enables localization and identification of proteins via their related digested peptides. In a number of cases, ion mobility separates isobaric ions that cannot be identified by conventional MALDI time-of-flight (TOF) mass spectrometry. The amount of detected peaks per measurement increases (versus conventional MALDI-TOF), which enables mass and time selected ion images and the identification of separated ions. These experiments demonstrate the feasibility of direct proteins identification by ion-mobility-TOF IMS from tissue. The tissue digestion combined with MALDI-IM-TOF-IMS approach allows a proteomics "bottom-up" strategy with different kinds of tissue samples, especially FFPE tissues conserved for a long time in hospital sample banks. The combination of IM with IMS marks the development of IMS approaches as real proteomic tools, which brings new perspectives to biological studies. (J Am Soc Mass Spectrom 2010, 21, 338 -347)

The high chemical complexity of the lipidome is one of the major challenges in lipidomics research. Ion-mobility spectrometry (IMS), a gas-phase electrophoretic technique, makes possible the separation of ions in the gas phase according to their charge, shape, and size. IMS can be combined with mass spectrometry (MS), adding three major benefits to traditional lipidomic approaches. First, IMS-MS allows the determination of the collision cross section (CCS), a physicochemical measure related to the conformational structure of lipid ions. The CCS is used to improve the confidence of lipid identification. Second, IMS-MS provides a new set of hybrid fragmentation experiments. These experiments, which combine collision-induced dissociation with ion-mobility separation, improve the specificity of MS/MS-based approaches. Third, IMS-MS improves the peak capacity and signal-to-noise ratio of traditional analytical approaches. In doing so, it allows the separation of complex lipid extracts from interfering isobaric species. Developing in parallel with advances in instrumentation, informatics solutions enable analysts to process and exploit IMS-MS data for qualitative and quantitative applications. Here we review the current approaches for lipidomics research based on IMS-MS, including liquid chromatography-MS and direct-MS analyses of "shotgun" lipidomics and MS imaging.