A crucial and challenging aspect of the drug development process is the requirement to measure the distribution of a pharmaceutical compound and its metabolites in tissue. Industry-standard methods used to look at total localisation of drug-related material are limited due to their dependence on labels. These labelled techniques can have difficulty in distinguishing between the drug of interest and its metabolites. Imaging mass spectrometry is a technique that has the potential to spatially distinguish between drug and metabolites, due to its high chemical specificity and sensitivity. A number of imaging mass spectrometry approaches have been described for localisation of drug compounds in tissue, most notably matrix-assisted laser desorption/ionisation (MALDI) imaging, which can provide data complementary to existing imaging techniques. Two imaging mass spectrometry approaches have been evaluated and compared for use in the localisation of a range of drug compounds in target tissues. The techniques used were MALDI imaging and a recently described electrospray ionisation-based technique, liquid extraction surface analysis (LESA). Both techniques have been successfully used for the detection of drug compounds in dosed tissue sections. A major challenge associated with imaging techniques is the required selectivity of the experiment for the compound of interest, due to the complex nature of tissue sections. Combining the shape-selective method of ion mobility separation with MS/MS fragmentation has been shown to improve the selectivity of both imaging approaches for the compound of interest. Results obtained using LESA-MS have demonstrated the suitability of this technique as a rapid and sensitive profiling technique for the detection of drugs and metabolites in tissue, but with a lower achievable spatial resolution than MALDI imaging. Higher spatial resolution was achieved with MALDI imaging; however data acquisition times were longer and required higher dosing levels for successful detection of drug compounds in tissue. A biological application of MALDI imaging was also evaluated. Mobility-enabled MALDI imaging was used to assess differences in the localisation of important adenine nucleotides between control and metabolically stressed mouse brain sections. Tissue fixation methods were evaluated to overcome rapid post-mortem degradation of adenine nucleotides such that biologically relevant localisation images can be obtained. These studies highlight the crucial importance of appropriate biological sample preparation in MALDI imaging experiments.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:582369 |
| Date | January 2013 |
| Creators | Blatherwick, Eleanor Q. |
| Publisher | University of Warwick |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://wrap.warwick.ac.uk/57257/ |
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