REPOSITORY > RESULTS

Abstract

Medicine relies on imaging techniques such as ultrasound, magnetic resonance, computed tomography and histopathological image analysis because they provide valuable data needed for the diagnosis and treatment of diseases and injuries. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) is often used in research and for the advanced diagnosis and clinical treatment of different diseases and injuries. LA-ICP-MS is an instrumental analytical technique that is used for the spatially resolved microanalysis of solid samples and is capable of quantitative mapping (imaging) of metals and metalloids in tissue samples of animal or plant origin in a selected area of interest.
In this dissertation, LA-ICP-MS was used for the bioimaging of Pt from Pt-based chemotherapeutics in tumour samples. High sensitivity and the ability to create quantitative images with the 3D sample reconstruction of this technique allowed us to determine the quantitative Pt distribution in HT29 tumour spheroids treated with cisplatin (CDDP) or Texas Red cisplatin (TR-CDDP). Under optimized instrumental parameters, a high spatial resolution and high sensitivity, with low limits of detection was achieved. Matrix-matched gelatine standards and/or isotope dilution analyses were used to quantify the amount of Pt. The results of the LA-ICP-MS analysis revealed that the Pt in the CDDP-treated tumour spheroids was localized primarily in the outer rim of the spheroids and to a lesser extent in the intermediary layer and the necrotic core. Due to the steric effects, significantly lower Pt concentrations were accumulated in the spheroids treated with TR-CDDP (2.2-times lower than in the CDDP-treated spheroids), while the Pt was mostly distributed in the areas of the outer rim. Imaging with confocal fluorescence microscopy, which is commonly used in oncology research, was compared with that by LA-ICP-MS. The results of the two complementary techniques demonstrated good agreement in terms of the spatial distribution of the TR-CDDP, while the intensity of the fluorescence matched well with the concentrations of Pt determined with LA-ICP-MS.
The developed method was further applied for studying drug distribution and uptake on tumours of B16F10 and 4T1 cancer cell lines. Different drug application methods and exposure times were tested at the same CDDP dosage and characterised using LA-ICP-MS. Intratumoral application oversaturates the tumour tissue, entering into the tumour environment and bloodstream. The results show that intratumorally injected samples release CDDP with time. However, the CDDP concentrations in tumour tissue were significantly higher than in intravenous injection. When injected intravenously, CDDP binds unspecifically to DNA and proteins throughout the whole organism. Consequently, a lower CDDP concentration is delivered to the targeted tumorous tissue. Therefore, to achieve the same drug concentration in the tumour, a smaller dosage is needed with intratumoral administration. This allows for a more targeted approach, with reduced side effects from the treatment.
The potential to extend the applicability of the developed LA-ICP-MS method for other solid biological samples was proved by an analysis of Cr localisation in the leaves of the dandelion plant (Taraxacum officinale).