Fundamental aspects of imaging matrix assisted laser desorption ionisation mass spectrometry.

Matrix assisted laser desorption/ionisation mass spectrometry imaging is a recent addition to the existing family of molecular imaging technologies. It has the capacity to map the distribution of molecules within a biological tissue section, without the need for radionuclide or fluorescent labelling procedures. The primary aim of the work presented in this thesis was to assess the use of a high repetition rate laser for MALDI-MS image analysis by developing methodologies for the detection of a number of different compounds from a variety of biological tissues. Additional investigations include and examination of strategies for normalisation and statistical interpretation of MALDI-MS image data. The application of a solvent assisted indirect imaging approach for the analysis of drugs in skin is described. Studies have been carried out in order to gauge how the use of a solvent in the blotting process aids the indirect imaging technique. Further experiments have been performed to assess the level of analyte migration induced by incorporation of a sample wetting step. In a direct tissue imaging experiment the distribution of a prodrug and its active metabolite has been determined in treated tumour tissue. Endogenous markers have been employed to assist in determining correlation between drug activation and hypoxic regions within tumours. Different methods of data normalisation are investigated for their effects on image data, and statistical evaluation of MALDI-MS acquired image data have been examined in relation to extracting hidden variables from multidimensional image data sets.