Malaria continues to wreak havoc in tropical regions, due largely to the lack of an effective vaccine. Vaccine candidates based on whole parasites have shown promising results in malaria-naïve... Show moreMalaria continues to wreak havoc in tropical regions, due largely to the lack of an effective vaccine. Vaccine candidates based on whole parasites have shown promising results in malaria-naïve individuals, but their potency in malaria-exposed individuals is considerably lower. This dissertation described the development of a chemical strategy for boosting such parasites’ potency in pursuit of more efficacious malaria vaccines for use in endemic areas.Chapter 2 outlined the adaptation of a method for chemically modifying microbial cell surfaces.Chapter 3 showed the chemistry underlying this modification system to be stably compatible with in vivo usage.Chapter 4 demonstrated that when the chemical modification system was used to introduce immune-potentiating agents onto bacteria, better immune responses ensued.Chapter 5 tied it all together by using the chemical modification system to potentiate malaria parasites, and showed that doing so markedly improved immune responses in an in vivo immunization model.Chapter 6 summarized these findings in the context of malaria vaccine development and posited next steps forward. Show less
Welling, M.M.; Spa, S.J.; Willigen, D.M. van; Rietbergen, D.D.D.; Roestenberg, M.; Buckle, T.; Leeuwen, F.W.B. van 2019
In this thesis the thermal- and photo-substitution behavior of polypyridyl ruthenium complexes is described at the surface of lipid bilayers and in homogeneous solutions. It is shown that the... Show moreIn this thesis the thermal- and photo-substitution behavior of polypyridyl ruthenium complexes is described at the surface of lipid bilayers and in homogeneous solutions. It is shown that the successive thermal binding and light-induced unbinding of the cationic ruthenium complex at the surface of the lipid bilayer requires negatively charged liposomes and ruthenium complexes containing moderately hindered N-N bidentate ligands. Our results in homogeneous solution show that changing the steric hindrance of the bidentate ligand influences both the photo- and thermal reactivities of these complexes, by altering the mechanism of the Ru-S bond formation. It is also shown that the Ru-S bond formation at the surface of negative lipid bilayers is faster than the same reaction in homogenous aqueous solutions, and a two-steps mechanism is proposed for the thermal coordination of ruthenium aqua complexes at membrane-embedded ligands. Furthermore, the application of ruthenium-functionalized liposomes in drug delivery is discussed. In vitro tests on cancer cell lines show that neutral liposomes functionalized with ruthenium compounds are more readily taken up by cancer cells than ruthenium-free liposomes. The liposome samples with ruthenium compounds are shown to be poorly cytotoxic in the dark. After light irradiation, the cytotoxicity increased at least up to five times for ruthenium complexes supported on non-PEGylated liposomes. Finally, the photoactivation of polypyridyl complexes with low-energy photons was studied using a photosensitization approach. A photosubstitution reaction was made faster upon yellow light irradiation than upon blue light irradiation by covalently linking a rhodamine B dye to the ruthenium complex. Show less
In this thesis the behavior and functionality of peptide amphiphiles at the surface of bilayer vesicles is examined. By controlling the behavior of the surface bound peptides, I was able to... Show moreIn this thesis the behavior and functionality of peptide amphiphiles at the surface of bilayer vesicles is examined. By controlling the behavior of the surface bound peptides, I was able to construct assemblies which could: 1) release their content (triggered by pH), 2) fuse in a targeted and controlled manner or 3) dock to cells and zebrafish embryos Show less
Of the various biomolecular building blocks in use in nature, coiled-coil forming peptides are amongst those with the most potential as building blocks for the synthetic self-assembly of... Show moreOf the various biomolecular building blocks in use in nature, coiled-coil forming peptides are amongst those with the most potential as building blocks for the synthetic self-assembly of nanostructures. Native coiled coils have the ability to function in, and influence, complex systems composed of multiple building blocks. However, there have only been a limited number of synthetic coiled-coil assemblies that mimic native coiled coils by incorporating multiple assembling components. This thesis represents efforts at extending this aspect of coiled-coil self-assembly. In order to achieve this, a range of hybrid molecules were synthesized which combine coiled-coil peptides with a hydrophobic component. In this way the highly specific coiled-coil self-assembly is juxtaposed with the non-specific, but structure-inducing aggregation of the hydrophobic section. This thesis asked simple questions: can coiled coils function when covalently attached to large hydrophobic blocks? How large can the hydrophobic blocks be? Can coiled coils function when incorporated noncovalently with a supramolecular assembly? By answering these fundamental questions the possibilities of prescriptive self-assembly have been probed and expanded, novel preparative methods have been developed, and specific applications have arisen. Show less
