Chakif, Dib (2025). Comparative Study of Chelating Agents in the Treatment of Heavy Metal Poisoning on Early Zebrafish Embryo Development followed by Quantitative PCR Studies. (Thesis). Universität Bern, Bern
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Abstract
This dissertation encompasses two interdisciplinary research projects addressing scientific challenges. The first project focused on heavy metal intoxication and the evaluation of five chelation therapies to determine the most effective treatment strategies by using zebrafish embryos as a model organism—chosen for their rapid development, genetic tractability, and transparent physiology. Heavy metals such as mercury, lead, and cadmium are highly toxic, often accumulating in critical organs and leading to severe health consequences. Chelation therapy, which introduces sulfur-based ligands such as alpha-lipoic acid (ALA), dimercaptosuccinic acid (DMSA), dimercaptopropanesulfonic acid (DMPS), cysteine (L-CYS), and glutathione (L-GSH), is used to remove these toxic metals from the body. However, the comparative effectiveness of these agents remains poorly understood. Our study first evaluated the stability of these compounds in zebrafish embryo medium using Nuclear Magnetic Resonance (NMR) spectroscopy. We then established the lowest toxic concentrations of Pb, Cd, and Hg in zebrafish embryos. Finally, we tested the efficacy of chelating agents in reversing toxicity. Results showed that DMSA, DMPS, L-CYS, and L-GSH effectively rescued mercury-poisoned embryos, while ALA did not. For cadmium, only DMSA and DMPS were effective. Lead was more tolerated than cadmium. Additionally, qPCR analysis revealed gene expression alterations caused by metal exposure that were partially reversed by chelation. These findings offer valuable insights into optimizing chelation therapy for heavy metal poisoning. The second project focused on pharmaceutical sciences, specifically the formulation and design of liposomal drug delivery systems incorporating ruthenium(II)-based metal complexes for targeted cancer therapy. This work aimed to develop stable liposome-based formulations capable of efficiently delivering cytotoxic agents to cancer cells. Liposomes, especially in the form of small unilamellar vesicles (SUVs), are widely used in biomedical applications due to their favorable stability, biodistribution, and ability to encapsulate both hydrophilic and hydrophobic drugs. We first investigated the structural and dynamic properties of liposomes prepared from DOPC, POPC, and DPPC phospholipids, transitioning from multilamellar vesicles (MLVs) to SUVs. Dynamic Light Scattering (DLS) and High-Resolution Magic Angle Spinning Nuclear Magnetic Resonance (HR-MAS NMR) spectroscopy were employed to analyze size distribution and molecular interactions. Optimized extrusion techniques yielded monodisperse SUV populations with stability exceeding three months, confirming the importance of precise liposomal formulation methods for reproducible and effective drug delivery. Concurrently, we studied six novel cytotoxic cationic dinuclear thiolato-bridged arene ruthenium(II) complexes, known for their potent anticancer activity, particularly against ovarian cancer cell lines (A2780 and A2780cisR). These complexes were investigated for their interactions with MLVs composed of DOPC, POPC, and DPPC using HR-MAS NMR techniques, including 1D, NOE, and DOSY spectroscopy. Results revealed: (i) specific, structure-dependent interactions between ruthenium complexes and lipid bilayers; (ii) the integrity of both the complexes and MLVs was preserved; (iii) complex localization within bilayers varied based on their chemical structure; (iv) intermolecular forces influence complex-liposome interactions. These findings enhance our understanding of ruthenium-liposome interactions and support the rational design of liposomal formulations for targeted delivery of metal-based anticancer agents, representing a promising direction in pharmaceutical development.
| Item Type: | Thesis |
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| Dissertation Type: | Single |
| Date of Defense: | 28 February 2025 |
| Subjects: | 500 Science > 540 Chemistry 500 Science > 590 Animals (Zoology) |
| Institute / Center: | 08 Faculty of Science > Department of Chemistry, Biochemistry and Pharmaceutical Sciences (DCBP) |
| Depositing User: | Hammer Igor |
| Date Deposited: | 04 Jun 2025 14:46 |
| Last Modified: | 04 Jun 2025 14:48 |
| URI: | https://boristheses.unibe.ch/id/eprint/6257 |
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