Lysosomal acid glucosylceramidase (GBA1) is a lysosomal enzyme that degrades glucolipids with its main substrate being glucosylceramide (GlcCer). Defects in the GBA1 gene lead to... Show moreLysosomal acid glucosylceramidase (GBA1) is a lysosomal enzyme that degrades glucolipids with its main substrate being glucosylceramide (GlcCer). Defects in the GBA1 gene lead to glycosphingolipidosis Gaucher disease (GD), in which the hydrolysis of GlcCer is impaired and therefore, it accumulates in the lysosome. GD has a wide range of phenotypes that reaches from asymptomatic to neuropathologic manifestations, which are lethal within the first years of life. Although various GBA1 mutations have been identified, they cannot be systematically matched with GD phenotypes. Therefore, this thesis aims to get a better understanding of GBA1 and its role in GD by identifying GBA1’s cellular interaction partners with the aid of an enrichment assay. For this assay, photocleavable activity-based probes (ABPs) were developed, which ought to be able to isolate GBA1 from a cell lysate together with its interaction partners with the aid of streptavidin-coated beads. By photocleaving the complex off the beads, the background of the GBA1-containing samples can be lowered. So far, GBA1 could successfully be isolated from a cell lysate with the developed ABPs. Next, the assay conditions need to be optimized for isolation of GBA1 together with its interaction partners. Show less
As leading cause of death worldwide, cancer is responsible for nearly 10 million deaths in 2020 according to World Health Organization (WHO). Cisplatin and its derivatives are commonly used... Show moreAs leading cause of death worldwide, cancer is responsible for nearly 10 million deaths in 2020 according to World Health Organization (WHO). Cisplatin and its derivatives are commonly used chemotherapy agents for current cancer treatment in the clinics. While such metallodrugs are urgent to be improved because they are often accompanied by severe side effects to the patients. Alternatively, ruthenium-based complex are considered as more promising candidates due to their appealing photochemistry and photophysical properties. These properties offer possibility to activate such complex by external light, which realizes a better partial targeting to tumor region and thus reduces the side effect of the metallodrugs. To further optimize the tumor selectivity of ruthenium complexes, in this thesis, a series of ruthenium(Ⅱ) polypyridine-peptide conjugates were synthesized differential in polypyridine ligand, peptide sequence, and/or chirality. Their structure, photochemistry, in vitro cellular behaviors, and in vivo antitumor efficiency, were widely studied and compared. My study confirmed that the conjugation of peptides with ruthenium complexes is one of the most promising tools for improving their potential as clinical drugs, which provides a strong basis for the design and application of more ruthenium-peptide candidates for active tumor targeting in the future. Show less
Moses, J.I.; Tremblin, P.; Venot, O.; Miguel, Y. 2022
Metal complexes and 2D materials like graphene were combined to produce structures that can function as sensors. Using spin crossover materials, both in bulk single crystal form and in thin layer... Show moreMetal complexes and 2D materials like graphene were combined to produce structures that can function as sensors. Using spin crossover materials, both in bulk single crystal form and in thin layer form, graphene-based electronic sensors were produced and characterized that can detect spin switches in the spin crossover materials. At the same time, the light-activatable ruthenium complexes were researched for their application in sensors that can monitor reactions that were triggered by light. We found that the photoreaction of a ruthenium complex with a nucleobase could be triggered in paper-based graphene devices. Moreover, we found that this ruthenium scaffold could also be used to increase the signal strength in a nanopore-based DNA detection system. Lastly, a ruthenium complex was designed that had a sensing function built in, as a dual-function molecule with a sensing and anticancer function. Overall, combining metal complexes with graphene was found to be a successful strategy to produce hybrid structures for sensing. Show less
Moses, J.I.; Tremblin, P.; Venot, O.; Miguel, Y. 2021
Astronomical observations of cold regions in the universe show a rich inventory of ices. Part of these ices may end up on planets like our own, but in that journey they will be exposed to... Show moreAstronomical observations of cold regions in the universe show a rich inventory of ices. Part of these ices may end up on planets like our own, but in that journey they will be exposed to considerable amounts of radiation. As water is the main component of these ices, the optical and photochemical properties of water ice largely determine how the radiation affects the molecules embedded in the ice. In this thesis, water ice is investigated as a host for photochemical reactions. A new laboratory setup is constructed, and two types of molecules are studied: glycine, an amino acid, and triphenylene, a polycyclic aromatic hydrocarbon. The photochemistry upon exposure to ultraviolet radiation is studied using UVvis and infrared spectroscopy. In addition, the optical properties of water ice are constrained in the UV-vis range, resulting in high-resolution optical constants, relevant for all ice-rich environments - from far away in space to our atmosphere. Water itself does not absorb light in this range, but as most organic molecules do, and are destroyed by radiation in this range, this is of high importance for molecules within the ice. Show less
Metal-based prodrugs based on ruthenium(II) polypyridyl complexes have proven to be very suitable for application in both photodynamic therapy (PDT) and photo-activated chemotherapy (PACT). As most... Show moreMetal-based prodrugs based on ruthenium(II) polypyridyl complexes have proven to be very suitable for application in both photodynamic therapy (PDT) and photo-activated chemotherapy (PACT). As most of these complexes unfortunately require poorly-penetrative, potentially-toxic blue light for their photo-activation, a lot of research effort has been dedicated to the development of prodrug systems that can be activated using near-infrared light, which is less harmful and penetrates deeper into human tissue. Thulium-doped upconverting nanoparticles (UCNPs) produce the desired blue light upon excitation with near-infrared light, allowing for the development of a drug delivery system in which ruthenium prodrugs are activated with near-infrared light. This thesis deals with the development of several new photo-activatable ruthenium polypyridyl complexes and the investigation of their photochemistry. Furthermore, a multicentre comparative study of the upconversion quantum efficiencies of LiYF4 UCNPs is reported. Finally, it describes the formation of water-dispersible UCNPs decorated with the newly-developed ruthenium complexes, as well as their stability in aqueous media and the successful photo-activation of the surface-bound ruthenium complexes using near-infrared light. The work has resulted in new insights into the design principles that are essential for the successful development of photo-activatable ruthenium-decorated upconverting nanoparticles. Show less
Siewert, B.; Langerman, M.; Pannwitz, A.; Bonnet, S.A. 2018
The main goal of the research described in this thesis was the development of new photoactivated chemotherapy (PACT) ruthenium(II) complexes bearing a non-toxic photolabile ligand. We first... Show moreThe main goal of the research described in this thesis was the development of new photoactivated chemotherapy (PACT) ruthenium(II) complexes bearing a non-toxic photolabile ligand. We first investigated whether non-toxic ligands such as L-proline, 2-(methylthio)methylpyridine (mtmp), or 3-(methylthio)propylamine (mtpa), once coordinated to ruthenium(II) complexes, could be photosubstituted upon visible light irradiation. The lipophilicity, and in some cases the strain of the ruthenium(II) complexes, were systematically varied and the effects of such variations on the cytotoxicity of the complexes in the dark and under light irradiation were studied. In the second part, the best ligand candidates (i.e. mtmp and mtpa) were coordinated to cyclometalated ruthenium complexes of the type [Ru(bpy)(phpy)(S,N)]PF6 (bpy = 2,2’-bipyridine and phpy = 2-phenylpyridine), to shift the absorption of the complex to the red region of the spectrum. The photosubstitution properties of these cyclometallated complexes were investigated in detail. The most promising ruthenium complexes were tested in cancer cell monolayers under hypoxic conditions (1% O2) to investigate their mode of action and distinguish between PACT and PDT. Show less
Ruthenium complexes are promising prodrugs in photoactivated chemotherapy (PACT): to prevent systemic therapeutic side-effects, a non-toxic version of the drug is introduced in the body and is... Show moreRuthenium complexes are promising prodrugs in photoactivated chemotherapy (PACT): to prevent systemic therapeutic side-effects, a non-toxic version of the drug is introduced in the body and is only activated at the place of the tumor by means of visible light irradiation. However, most of these PACT compounds are only sensitive for UV or blue light, while this light does not permeate the body very well, in contrast to red or near-infrared light. To circumvent this problem, the principle of light-upconversion can be used to "upgrade" red light to blue light in a drug carrier such as a nanovesicle: the tumor is irradiated with red light, after which blue light is generated locally and used to activate the prodrug. Among the various methods of light-upconversion, triplet-triplet annihilation upconversion (TTA-UC) was selected as the most promising. In this thesis it is described that green-to-blue and red-to-blue upconverting nanovesicles were prepared. The red-to-blue upconverted light was successfully used to activate a ruthenium polypyridyl complex that was anchored to the same vesicle. Finally, the inherent oxygen-sensitivity of TTA-UC was greatly mitigated by the addition of water-soluble and biocompatible anti-oxidants. We expect that the results of this thesis will lead to exciting applications in PACT. Show less
Mid-infrared (mid-IR) astronomical observations show that molecules freeze out on interstellar grains to form interstellar ices. These ices play an important role in the chemical evolution of... Show moreMid-infrared (mid-IR) astronomical observations show that molecules freeze out on interstellar grains to form interstellar ices. These ices play an important role in the chemical evolution of molecules in space. Understanding the physical interactions and chemical reactions that take place in these ices gives us important clues to how the ices are formed and which role they play in the formation of complex molecules. The physical interactions in H2O:CO binary ices and in CH3OH and NH3 containing ices are studied both in the laboratory and in space by means of mid-IR spectroscopy, resulting in the unambiguous detection of NH3 in a low-mass protostar. Additionally, mid-IR and near-UV/VIS spectroscopic measurements on the ultraviolet induced photochemistry of large molecules, Polycyclic Aromatic Hydrocarbons (PAHs), trapped in ices are described. These molecules are known to be abundantly present in space, but their influence on the chemical evolution of interstellar ices has never been studied in detail. The experiments indicate that the processes are important in the formation of complex and charged molecules and that new astrochemical models should take the role of PAHs in ice into account. Show less
Porphyrins are essential in living organisms. E.g. in the red oxygen carrying blood protein hemoglobin oxygen binds to the Fe2+-containing heme and in plants the green pigment chlorophyll is... Show morePorphyrins are essential in living organisms. E.g. in the red oxygen carrying blood protein hemoglobin oxygen binds to the Fe2+-containing heme and in plants the green pigment chlorophyll is responsible for the initial steps in photosynthesis. The absorption of light by a porphyrin, followed by energy transfer to oxygen can lead to the formation of highly toxic but short living singlet oxygen. When such a porphyrin localizes in a tumor it is possible to destroy the tumor locally by the irradiating it with light. This treatment is known as photodynamic therapy and the pigment is called a photosensitizer. However a major drawback of current photosensitizers is that they do not show strong absorption in the far-red part of the spectrum where light penetrates tissue optimal. Besides patients treated with these photosensitizers remain light sensitive for 3-8 weeks. This thesis describes the preparation of new photosensitizers with strong absorption of light at 680-690 nm. The preparation of these porphyrin derivatives takes place via unprecedented chemical reactions and an explanation for the chemistry involved is given. Tests on mice showed that the lifetime of these new porphyrin derivatives in their body is reduced to less then 3 days, which makes them very interesting candidates as new generation photosensitizers for photodynamic therapy Show less
The search for organic molecules and traces of life on Mars has been a major topic in planetary science for several decades, and is the future perspective of several missions to Mars. In order to... Show moreThe search for organic molecules and traces of life on Mars has been a major topic in planetary science for several decades, and is the future perspective of several missions to Mars. In order to determine where and what those missions should be looking for, laboratory experiments under simulated Mars conditions have been performed. This thesis describes the effects of simulated martian surface conditions on organic material (amino acids) and living organisms (halophilic archaea). Experiments have been performed to study the stability of thin films of glycine and alanine against UV irradiation under different conditions. Thin films of glycine and alanine have a half-life of 22 ± 5 hours and 3 ± 1 hours, respectively, when extrapolated to Mars-like UV flux levels in vacuum. The presence of a 7 mbar CO2 atmosphere does not affect these destruction rates. Cooling the thin films to 210 K (average Mars temperature) lowers the destruction rate by a factor of 7. The intrinsic amino acid composition of two martian soil analogues, JSC Mars-1 and Salten Skov, has been investigated. The results demonstrated that these analogues are inappropriate for a life-science study in their raw state. Besides amino acids, the response of the halophilic archaea Natronorubrum sp. strain HG-1 to Mars-like conditions, such as low pressure, UV radiation and low temperatures, has been studied. From the results we concluded that this strain would not be a good model organism to survive on the surface of Mars. Show less
