The presented study focuses on the development of a workflow to combine different chemical bioimaging modalities with laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) on a single tissue thin section. LA-ICP-MS was used to investigate elemental distributions in pancreatic tumor samples of mice injected with an iodine- and a gadolinium-based contrast agent and the chemotherapeutic agent cisplatin. The exogenous elements iodine, gadolinium and platinum were quantified using matrix-matched gelatin standards, while endogenous elements such as phosphorus, iron and zinc were analyzed qualitatively.

By using other element- or molecule-selective chemical imaging modalities, validating or complementary results could be obtained. Micro X-ray fluorescence (μXRF) was used for an elemental pre-screening of highly abundant elements. Infrared (IR) microspectroscopy and matrix-assisted laser desorption/ionization-mass spectrometry (MALDI-MS) were employed to obtain spatial molecular information e.g. on lipids. After method development for the individual modalities, different modalities were combined on the same tissue thin section. One challenge was the choice of carrier slide, as the different modalities require different slides. For example, conductive slides are required for MALDI-MS and IR-transparent or -reflective slides for IR microspectroscopy. Therefore, indium tin oxide (ITO) slides, which are already established for MALDI-MS and have been successfully used for IR microspectroscopy, were tested for the other modalities. Different section thicknesses were compared for the different modalities. Another challenge was the destructive character of some of the modalities. As μXRF and IR microspectroscopy are non-destructive, they can be performed before any of the other modalities. Since MALDI-MS is semi-destructive, while LA-ICP-MS is destructive, different parameters were varied to allow MALDI-MS prior to LA-ICP-MS analysis.