The external tissues of plants and animals are colonized by microbial communities termed microbiota. When organisms are exposed to environmental pollutants, these substances will therefore... Show moreThe external tissues of plants and animals are colonized by microbial communities termed microbiota. When organisms are exposed to environmental pollutants, these substances will therefore encounter microbiota at the exposure interface. Many antimicrobial substances have been found to disturb beneficial interactions between microbiota and the host, thereby impairing host health. Nanomaterials exhibit nanoscale properties that could affect host health in two additional, understudied, microbiota-dependent ways. Firstly, owing to their large surface area, adsorption interactions between nanomaterials, microbial metabolites and microbes could alter the identity and colloidal stability of nanomaterials, and may influence the dispersal of microbes. Secondly, the immuno-modulatory effects of microbiota could affect the sensitivity of hosts to immunotoxic nanomaterials. In this dissertation, we use a combination of computational techniques and zebrafish larvae experiments to unravel and quantify these interactions. We predict the affinity of microbial metabolites to carbon and metal nanomaterials, and show that titanium dioxide nanoparticles can affect the dispersal of microbes through aquatic ecosystems, and across different life stages of oviparous animals. Additionally, we provide insight into microbiota-dependent signaling pathways that affect the sensitivity of zebrafish larvae to particle-specific, immunotoxic effects of silver nanoparticles. Altogether, these results contribute to mechanistic pathways for microbiota-inclusive nanomaterial safety assessment. Show less
Ingested nanomaterials are exposed to many metabolites that are produced, modified, or regulated by members of the enteric microbiota. The adsorption of these metabolites potentially affects the... Show moreIngested nanomaterials are exposed to many metabolites that are produced, modified, or regulated by members of the enteric microbiota. The adsorption of these metabolites potentially affects the identity, fate, and biodistribution of nanomaterials passing the gastrointestinal tract. Here, we explore these interactions using in silico methods, focusing on a concise overview of 170 unique enteric microbial metabolites which we compiled from the literature. First, we construct quantitative structure–activity relationship (QSAR) models to predict their adsorption affinity to 13 metal nanomaterials, 5 carbon nanotubes, and 1 fullerene. The models could be applied to predict log k values for 60 metabolites and were particularly applicable to ‘phenolic, benzoyl and phenyl derivatives’, ‘tryptophan precursors and metabolites’, ‘short-chain fatty acids’, and ‘choline metabolites’. The correlations of these predictions to biological surface adsorption index descriptors indicated that hydrophobicity-driven interactions contribute most to the overall adsorption affinity, while hydrogen-bond interactions and polarity/polarizability-driven interactions differentiate the affinity to metal and carbon nanomaterials. Next, we use molecular dynamics (MD) simulations to obtain direct molecular information for a selection of vitamins that could not be assessed quantitatively using QSAR models. This showed how large and flexible metabolites can gain stability on the nanomaterial surface via conformational changes. Additionally, unconstrained MD simulations provided excellent support for the main interaction types identified by QSAR analysis. Combined, these results enable assessing the adsorption affinity for many enteric microbial metabolites quantitatively and support the qualitative assessment of an even larger set of complex and biologically relevant microbial metabolites to carbon and metal nanomaterials. Show less
This thesis focuses on the synthesis, characterization and performance towards CO2 electroreduction of mono and bi-metallic particles based on p-block metals. With an industrial perspective in mind... Show moreThis thesis focuses on the synthesis, characterization and performance towards CO2 electroreduction of mono and bi-metallic particles based on p-block metals. With an industrial perspective in mind, we try to synthesize particulate, high surface area materials with clean, scalable synthesis methods where possible and test their performance in H-Cell and gas diffusion electrode flow cell configurations. With a combination of characterization techniques, we find possible explanations for the catalytic behaviors. Show less
Similarity assessment is one of the means of optimally using scarcely available experimental data on the fate and hazards of nanoforms (NFs) for regulatory purposes. For a set of NFs that are shown... Show moreSimilarity assessment is one of the means of optimally using scarcely available experimental data on the fate and hazards of nanoforms (NFs) for regulatory purposes. For a set of NFs that are shown to be similar it is allowed in a regulatory context to apply the information available on any of the NFs within the group to the whole set of NFs. Obviously, a proper justification for such a similarity assessment is to be provided. Within the context of exemplifying such a justification, a case study was performed aimed at assessing the similarity of a set of spherical metallic NFs that different with regard to chemical composition (three metals) and particle size (three different sizes). The endpoints of assessment were root elongation and biomass increase of lettuce (Lactuca sativa L.) seedlings and exposure assessment was performed in order to express the actual exposure concentration in terms of time-weighted average particle concentrations. The results of the study show that for the specific endpoints assessed, chemical composition is driving NF toxicity and this is mostly due to impacts on the fate of the NFs. On the other hand, particle size of Cu NFs had a negligible impact on the dose-response relationships for the specific endpoints assessed. It is thus concluded that hazard data available on spherical Cu NF tested in our case can be used to inform on the hazards of any spherical Cu NF within the size range of 25–100 nm, but only applies for the certain endpoints. Also, toxicity data for the Cu2+-ion are suited for such a similarity assessment. Show less
Tumor heterogeneity favors tumor tissue to survive and resist drugs, leading to the failure of chemotherapeutic agents to induce a therapeutic response. In addition, the absorption mechanisms,... Show moreTumor heterogeneity favors tumor tissue to survive and resist drugs, leading to the failure of chemotherapeutic agents to induce a therapeutic response. In addition, the absorption mechanisms, metabolism and excretion of chemotherapeutic drugs, which are commonly used for cancer patients and the lack of specific targeting of these drugs can cause adverse effects on treated patients. Thus, the general objective of this thesis is to investigate the biological activity of targeted poly (lactic-co-glycolic acid) (PLGA) nanoparticles (NPs) as a drug delivery system (DDS) for carvedilol (CVDL) or oxaliplatin (OXA), in vitro and in vivo, to treat colorectal cancer (CRC). DDSs were formulated to achieve this goal. In chapters 2, 3 and 4, our studies were discussed in detail on the formulations and characterizations of NPs as DDSs with ideal characteristics to increase the therapeutic range of drugs at the tumor site. As well as the biological evaluation of these DDS when its anti-inflammatory activity (Chapter 2) and its antitumor activity in vitro (Chapters 2, 3 and 4) and in vivo (Chapters 3 and 4). Taken together, all the DDSs studied in this thesis were able to improve the chemotherapeutic efficiency of the drugs studied in Chapters 2, 3 and 4. Show less
In this work, we investigate the minute circular dichroism effects of single nanoparticles.To this aim, we apply photothermal imaging with a polarization-modulated heating beam. This new technique,... Show moreIn this work, we investigate the minute circular dichroism effects of single nanoparticles.To this aim, we apply photothermal imaging with a polarization-modulated heating beam. This new technique, which we call photothermal circular dichroism microscopy, probes circular dichroism in an absorption measurement, unlike other techniques which usually probe the extinction. We also investigate in detail how to avoid measurement artefacts such as leakage of linear dichroism and residual intensity modulation.We then study the CD of formally achiral and wet-chemically synthesized chiral nanoparticles. We find that the achiral spherical-like particles, can exhibit considerable circular dichroism, some of them display almost as strong CD as specially designed chiral particles. Furthermore, we find that the control of handedness of the synthesized chiral particles is only limited and that, even from a geometric perspective, the relation between the 3D shape of these particles and their handedness is not straightforward.In the last chapter, we apply our method to magnetic samples which exhibit circular dichroism through their magnetization but not due to their shape. The excellent sensitivity of photothermal microscopy not only allows us to perform magnetic imaging of particles, but we also succeeded in obtaining magnetization curves of single particles and estimating their magnetization. Show less
In cancer treatment, nanomedicines may be employed in an attempt to improve the tumor localization of antineoplastic drugs e.g. immunotherapeutic agents either through passive or active targeting,... Show moreIn cancer treatment, nanomedicines may be employed in an attempt to improve the tumor localization of antineoplastic drugs e.g. immunotherapeutic agents either through passive or active targeting, thereby potentially enhancing therapeutic effect and reducing undesired off-target effects. However, a large number of administrated nanocarriers often fail to reach the tumor area. In the present study, we show that photodynamic therapy (PDT) enhances the tumor accumulation of systemically administered lipid-PEG layer coated poly (lactic-co-glycolic acid) (PLGA) nanoparticles (NP). Intravital microscopy and histological analysis of the tumor area reveal that the tumor vasculature was disrupted after PDT, disturbing blood flow and coinciding with entrapment of nanocarriers in the tumor area. We observed that the nanoparticles accumulating after treatment do not confine to specific locations within the tumor, but rather localize to various cells present throughout the tumor area. Finally, we show by flow cytometry that NP accumulation occurred mostly in immune cells of the myeloid lineage present in the tumor microenvironment (TME) as well as in tumor cells, albeit to a lower extent. These data expose opportunities for combination treatments of clinical PDT with NP-based immunotherapy to modulate the TME and improve antitumor immune responses. Show less
The biological application of photoactivatable ruthenium anticancer prodrugs is limited by the need to use poorly penetrating high-energy visible light for their activation. Upconverting... Show moreThe biological application of photoactivatable ruthenium anticancer prodrugs is limited by the need to use poorly penetrating high-energy visible light for their activation. Upconverting nanoparticles (UCNPs), which produce high-energy light under near-infrared (NIR) excitation, can solve this issue, provided that they form stable, water (H2O)-dispersible nano-conjugates with the prodrug and that there is efficient energy transfer from the UCNP to the ruthenium complex. Herein, we report on the synthesis and photochemistry of the ruthenium(II) polypyridyl complex [Ru(bpy)(2)(3(H))](PF6)(2) ([1](PF6)(2)), where bpy = 2,2-bipyridine and 3(H) is a photocleavable bis(thioether) ligand modified with two phosphonate moieties. This ligand was coordinated to the ruthenium center through its thioether groups and could be dissociated under blue-light irradiation. Complex [1](PF6)(2) was bound to the surface of NaYF4:Yb3+,Tm3+@ NaYF4:Nd3+@NaYF4 core-shell-shell (CSS-)UCNPs through its bis(phosphonate) group, thereby creating a H2O-dispersible, thermally stable nanoconjugate (CSS-UCNP@[1]). Conjugation to the nanoparticle surface was found to be most efficient in neutral to slightly basic conditions, resulting in up to 2.4 x 10(3) Ru-II ions per UCNP. The incorporation of a neodymium-doped shell layer allowed for the generation of blue light using low-energy, deep-penetrating light (796 nm). This wavelength prevents the undesired heating seen with conventional UCNPs activated at 980 nm. Irradiation of CSS-UCNP@[1] with NIR light led to activation of the ruthenium complex [1](PF6)(2). Although only one of the two thioether groups was dissociated under irradiation at 50 W.cm(-2), we provide the first demonstration of the photoactivation of a ruthenium thioether complex using 796 nm irradiation of a H2O-dispersible nanoconjugate. Show less
Gold nanoparticles show surprisingly strong interactions with light in the visible range, which can be divided into scattering, absorption, and photoluminescence. When a nanoparticle absorbs light,... Show moreGold nanoparticles show surprisingly strong interactions with light in the visible range, which can be divided into scattering, absorption, and photoluminescence. When a nanoparticle absorbs light, the corresponding energy is converted to heat, which can affect the environment of the (hot) nanoparticle. This thesis uses scattering and photoluminescence to study the behaviour of optically heated single gold nanoparticles: it discusses the behaviour of single plasmonic vapour nanobubbles, which occur around highly heated nanoparticles immersed in a liquid, the detection of chirality in nano-objects through their absorption and the photothermal effect, the behaviour of gold nanoparticles under sub-picosecond pulsed excitation, and the temperature dependence of pulse-excited photoluminescence of such particles. Show less
This thesis aimed to investigate the impact of exposure dynamics, relative contributions of ENPs(particle) and ENPs(ion), and dosing regimens on the toxicity of ENPs varying in different physico... Show moreThis thesis aimed to investigate the impact of exposure dynamics, relative contributions of ENPs(particle) and ENPs(ion), and dosing regimens on the toxicity of ENPs varying in different physico-chemical properties, on the composition and functioning of soil microbial communities. The physico-chemical properties of ENPs could change their fate, and the exposure dynamics thus need to be taken into consideration for realistically characterizing the time-variable exposure in assessing toxicity. The metabolic profile of microbial community could change according to ENPs shapes, with nanoplates being more toxic than nanospheres and polygons. Regarding the microbial community composition, the effect of ENPs depended on exposure time and concentration. However, the alterations in community composition were not expressed in terms of community functioning, which indicates that genus specific changes occurred but not yet necessarily reflected biological significance with regard to community functioning. Functional redundancy might contribute to community tolerance to ENPs exposure. When exposed to more realistic ENPs exposure scenarios with multiple dosing frequencies instead of one-time injection, the repetitive exposure with low-dosing could induce a tendency towards larger alteration of both community composition and functioning. Our study thus provided further insights in understanding the impact of NPs on soil microbial communities towards environmentally relevant assessment. Show less
The aim of this thesis was to investigate the feasibility of multimodal visualization techniques to observe adult stem cells, in particular HFBSCs, in the living animal. Due to the novelty of... Show moreThe aim of this thesis was to investigate the feasibility of multimodal visualization techniques to observe adult stem cells, in particular HFBSCs, in the living animal. Due to the novelty of HFBSCs in the field of inner ear research, a series of proof-of-principle experiments have been undertaken to investigate if these cells can undergo neuronal differentiation, tolerate genetic modification with lentiviral constructs containing the genes coding for reporter proteins, and tolerate subsequent loading with nanoparticles in vitro. In addition, it was of importance to examine if HFBSCs do integrate into modiolar tissue and if they can be visualized in the cochlea of the guinea pig. Lastly, we performed in vivo studies to investigate the ototoxic effect of ouabain in guinea pigs and the behavior of HFBSCs in mice with traumatic brain injury. Show less
Cathodic corrosion is a relatively unknown phenomenon that can severely etch metallic electrodes at cathodic (negative) potentials. In spite of these remarkable changes that are caused by cathodic... Show moreCathodic corrosion is a relatively unknown phenomenon that can severely etch metallic electrodes at cathodic (negative) potentials. In spite of these remarkable changes that are caused by cathodic corrosion, the phenomenon is stil not fully understood. Cathodic corrosion is therefore the focus of this PhD thesis. The first three experimental chapters of the thesis focus on characterizing platinum, rhodium and gold electrodes before and after cathodic corrosion in a variety of working solutions. In doing so, these chapters establish surprisingly mild corrosion onset potentials and reveal an etching anistropy that depends on the cation in the working solution. Additional density functional theory calculations suggest a similarly significant role for adsorbed hydrogen. These result suggest the existence of ternary metal hydrides during cathodic corrosion. The role of hydrides is further studied in the fourth experimental chapter through X-ray absorption spectroscopy. These four fundamental chapters are followed by two more applied chapters. The first of these tailors the activity of a platinum single crystal towards oxygen reduction, by using cathodic corrosion. The second applied chapter uses cathodic corrosion to create and thoroughly characterize alloyed nanoparticles. Combined, these fundamental and applied chapters provide valuable new information towards understanding and applying cathodic corrosion. Show less
In summary, the collective results described in this thesis show that nanoparticulate vaccines can be delivered intradermally by coated and hollow microneedles and evoke antigen-specific immune... Show moreIn summary, the collective results described in this thesis show that nanoparticulate vaccines can be delivered intradermally by coated and hollow microneedles and evoke antigen-specific immune responses. The choice of both the nanoparticles and the microneedle(s) could have important influences on the immune responses. Microneedle arrays coated with antigen loaded and lipid bilayer fused mesoporous silica nanoparticles (MSNs) could be a promising system for convenient and fast intradermal delivery of protein antigen, although our results indicate that the system needs to be improved in order to obtain optimal immune responses. Moreover, antigen and adjuvant loaded nanoparticles can increase IgG2a (Th1) and CD8+ responses after intradermal delivery by hollow microneedles. This effect depends on the type and the physicochemical characteristics of the nanoparticles, in which smaller size and controlled release properties of antigen and adjuvant were found to correlate with the stronger effect. Finally, the combination of separate antigen loaded and adjuvant loaded nanoparticles may be as efficient as the antigen and adjuvant co-encapsulated nanoparticles for modification of the immune responses following intradermal immunization. Show less
Synthetic long peptides (SLP) derived from cancer-associated antigens hold great promise as well-defined antigens for cancer immunotherapy. Clinical studies showed that SLP vaccines have... Show more Synthetic long peptides (SLP) derived from cancer-associated antigens hold great promise as well-defined antigens for cancer immunotherapy. Clinical studies showed that SLP vaccines have functional potency when applied to pre-malignant stage patients, but need to be improved for use as a therapeutic intervention against tumours. So far, SLPs have been administered in Montanide ISA-51, a water-in-oil formulation with reported important drawbacks and induced local side effects. Therefore, there is an urgent need for replacement of Montanide by more potent and safe alternatives. In this thesis, the concept of cationic liposome-based formulations was introduced, as the backbone for improved delivery of SLPs for cancer therapeutic vaccination. The developed formulation’s ability to induce efficient immune responses able to control tumour outgrowth in aggressive independent tumour models, makes cationic liposomes a very promising platform for SLP-based cancer immunotherapy. Their flexibility regarding the properties of loaded SLPs, their relative inexpensive production and the possibility to administer them via different delivery routes are all in favour for liposomal SLP-based cancer immunotherapy to become reality soon. Show less
