Proteins and organothiols are known for their high binding affinity to noble metal surface including gold nanoparticles (AuNPs). Numerous reports have been dedicated to AuNP interaction with protein or organothiol alone. Competitive protein and organothiol (OT) interaction is, however, mostly an unexplored area. The research reported here focused on developing a fundamental understanding of sequential and simultaneous protein and organothiol interaction with AuNPs in which protein and OT are added either simultaneously or sequentially into the colloidal AuNP solutions. In studies of OT interactions with bovine serum albumin (BSA) stabilized AuNPs, we found that the protein coating layer is highly porous and permeable for small molecules such as mercaptobenzimidazole (MBI), cysteine (Cys), homocysteine (Hcy), and glutathione (GSH). Based on the amounts of MBI adsorbed and the kinetics of MBI adsorption onto BSA stabilized AuNPs, we were able to get an insight into protein conformational changes on the AuNPs. The competitive and sequential studies of protein and OT interactions with AuNPs involving eight model organothiols showed that the protein and OT cosorption onto AuNPs is a kinetically controlled process. The AuNP stability against ligandsorption-induced AuNP aggregation differed significantly among the AuNP/OT and AuNP/BSA/OT mixtures where the AuNP stability order increased from (AuNP/OT)/BSA to AuNP/(BSA/OT), and finally (AuNP/BSA)/OT samples (the two components inside the parenthesis are mixed first followed by the addition of the third component). The studies on the role of cysteine in protein-AuNP interactions found that the cysteine has no significant effect on the kinetics of protein adsorption onto AuNPs. However the stability of the protein-AuNP complex against the organothiolsorption induced AuNP aggregation increased as the number of cysteine residues increased from zero to two. Besides providing new insights on protein interaction with AuNPs, this research is important for AuNP biological/biomedical applications because AuNPs in biofuids encounter a mixture of proteins and OTs in addition to other molecular species.

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Nanomaterials are widely used as pseudostationary and stationary phases in electrically driven capillary separations. The advantages of nanomaterial incorporation into capillary electrophoresis (CE) are numerous and include tunable sizes, multiple core compositions, flexible injection/introduction methods in separation techniques, and diverse surface chemistry options. Nanomaterials, however, exhibit inherently large surface energies which induce aggregation and as a result, yield unpredictable function in separations. Because nanomaterials can modify buffer conductivity, viscosity, and pH; separation optimization and nanoparticle stability must be considered. Successful incorporation of nanomaterials into reproducible separations requires (1) strict nanomaterial synthetic control and (2) detailed characterization of the nanoparticle in terms of both core material and surface chemistry. For this reason, this dissertation investigates how the surface chemistry on and morphology of gold nanoparticles impact capillary electrophoresis separations. The gold nanoparticle core composition, shape, size, self assembled monolayer (SAM) formation kinetics, and SAM ligand packing density are all evaluated for thioctic acid, 6-mercaptohexanoic acid, or 11-mercaptoundecanoic acid monolayers. Transmission electron microscopy (TEM), 1H NMR, extinction spectroscopy, zeta potential, X-ray photoelectron spectroscopy (XPS), and flocculation studies are used to assess the morphology, surface chemistry, optical properties, surface charge, SAM packing density, and effective stability of carboxylated nanoparticles, respectively. Using these well-characterized nanostructures, applications of gold nanoparticle pseudostationary phases in capillary electrophoresis is studied. Gold nanoparticles functionalized with mixed SAMs composed of thioctic acid and either 6-mercaptohexanoic acid or 6-aminohexanethiol impact the mobility of possible Parkinson's disease biomarkers in a concentration and surface chemistry dependent manner. From these data, a critical nanoparticle concentrations is developed to characterized nanoparticle stability during capillary electrophoresis separations. To understand the function of these and other carboxylated gold nanoparticles, extended DLVO theory is used to model interparticle interactions during electrically driven flow. 11-Mercaptoundecanoic acid functionalized gold nanoparticles suppress current, while 6-mercaptohexanoic acid and thioctic acid functionalized nanoparticles enhance separation current. Nanoparticle aggregation leads to electron tunneling effects between nanoparticles thereby increasing currents in poorly ordered SAMs while highly packed monolayers induce reversible flocculation characteristics and reduce current. In all cases, these effects are dependent on nanoparticle concentrations. Finally, surface chemistry optimized carboxylic acid functionalized gold nanoparticles effect the separation of hypothesized Parkinson's disease biomarkers. SAM composition and surface coverage impact separation efficiency, resolution, and selectivity. These effects are most systematic with well ordered SAMs. To understand the mechanism functionalized gold nanoparticles exhibit during a separation, their zeta potential with and without dopamine are evaluated. Nanoparticle to dopamine mole ratios (i.e. large dopamine concentrations), neutralize the three functionalized gold nanoparticles according to a dose response curve. The positively charged dopamine molecules saturate the negatively charged nanoparticle surfaces and aggregate thereby providing a plausible explanation to the biomarker concentration trends observed in capillary electrophoresis. These and future studies provide a rigorous experimental and theroretical evalauation of how nanoparticle structure impacts their function as pseudostationary phases in separations and other applications.

The exploration of nanoparticles for applications in medicine has grown dramatically in recent years. Due to their size, nanoparticles provide an ideal platform for combining multiple functionalities and interfacing directly with the biological realm. Additionally, nanoparticles can have physical properties that don't naturally exist in biology. Metal nanoparticles in particular have unique optical and magnetic properties which have driven nanomaterials research. The optical properties of gold nanoparticles and the magnetic properties of iron nanoparticles make them suitable for use as contrast agents in diagnostics and for radiation enhancement in therapeutic applications. The strong optical absorption and scattering and the nature of the conduction electrons of gold particles makes them ideal contrast agents for two-photon microscopy, photoacoustic imaging, and photothermal therapy. The superparamagnetic nature of iron oxide nanoparticles is clearly visible in magnetic resonance imaging, rendering them suitable as whole-body imaging contrast agents. All nanoparticle types can serve as delivery vehicles for drugs consisting of small molecules, peptides, or nucleic acids. This multiplicity of characteristics renders nanoparticles suitable for use in combining diagnosis and therapy, such as using particles to first detect the spatial extent of a cancer, and then to enhance near-infrared radiation in the tissue optical window to induce localized heating of diseased tissue. This combined approach requires both a mechanism of enhanced imaging contrast and a localized therapeutic mechanism, and the studies presented in this dissertation present work both on these aspects. By coating iron oxide nanoparticle cores with gold shells, it is possible to obtain a nanoparticle with both magnetic and optical properties. While individual gold nanoparticles do not absorb light in the infrared, receptor-mediated aggregation and the plasmon coupling effect lead to enhanced optical absorption only in diseased tissue. In addition to exploring these advanced applications, this work presents a fundamental investigation into the stability of gold nanoparticles in biological media. A previously unknown mechanism of gold nanoparticle destabilization and opsonization is presented and supported, along with a technique for reducing this opsonization and greatly enhancing the stability of gold particles in biological applications. This work will provide guidance to future designs of nanoparticle systems. / text

La synthèse de nanoparticules (NPs) d’or fonctionnalisées en phase aqueuse est encore aujourd’hui un enjeu majeur de la recherche dans le domaine des nanomatériaux. Depuis les travaux de J. Turkevich de 1951, la synthèse utilisant le citrate comme ligand et agent réducteur est la méthode de choix pour obtenir des NPs d'or. Cependant cette synthèse nécessite une étape supplémentaire de modification de surface par échange de ligand, pour pouvoir accrocher des molécules d’intérêt. Afin de simplifier la procédure, notre projet propose de synthétiser en une seule étape des NPs qui possèdent un groupement permettant une post-fonctionnalisation. La nouvelle voie de synthèse fait intervenir des composés bifonctionnels de la famille des 1-hydroxy-1,1-méthylène bisphosphonates (HMBP). Ainsi la base conjuguée de l'acide (1-hydroxy-1-phosphonopent-4-ènyl) phosphonique (HMBPène), qui possède une fonction éthylénique terminale nous a permis d'obtenir des dispersions de nanosphères de tailles contrôlées et nous avons pu rationaliser le mécanisme de synthèse utilisant ce type de molécules. Nous avons ensuite évalué plusieurs modalités de post-fonctionnalisation de notre nanoplateforme et validé une approche par chimie « Click » la via cycloaddition de composés tétrazine. En utilisant une nouvelle classe de HMBP couplés à une chaine polyéthylène glycol, des NPs stables en milieu physiologique ont pu être synthétisées selon le même modèle. Elles offrent également des possibilités de post-fonctionnalisation par couplage carbodiimide, que nous avons illustré par le couplage d'un fluorophore. Nous développons en dernière partie les résultats préliminaires sur deux types NPs d'or synthétisées à l'aide des HMBP pour des applications thérapeutiques. / In the ever growing fields of nanoscience the control of the synthesis of gold nanoparticles (GNPs) owing to their large variety of applications has emerged as an important domain. Among all methodologies Turkevich-Frens synthesis using citrates that act as ligand and reducing agent remains a method of choice for the obtaining of water soluble GNPs. Nevertheless, in post-synthesis, citrates are often exchanged with other ligands to enhanced stabilization and allow further functionalisation. In our work we present a new class of bi-functional molecules (1-hydroxy-1,1-methylene bisphosphonates HMBP) that can both reduce Au(III) and act as an efficient stabilizer of the formed GNPs in water. The first size controlled GNPs “one pot” synthesis was achieved by using an alkene conjugated HMBP, the (1-hydroxy-1-phosphonopent-4-enyl)phosphonic acid (HMBPene). We moreover, rationalized the mechanism of the GNPs synthesis using this type of molecule. We then, evaluated several methodologies for the post-functionalization of our nanoplateform and developed a « Click » chemistry approach to nanoparticle coating by tetrazine cycloaddition. Other nanoplatforms were synthesized using pegylated hydroxyl methylene bisphosphonates. This new class of bisphosphonate coated GNPs showed an improved stability in biological media and brought reactive groups available for post-functionalization as well, illustrated by the coupling of a fluorescent dye. The last part of this was dedicated to our latest results on GNPs synthesis for biomedical applications with HMBP compounds.

M.Sc. (Chemistry) / Loading gold nanoparticles (Au NPs) on mesoporous materials via different methods has been reported in the literature. However, the immobilisation of the dendrimer-encapsulated Au NPs on materials is still considered amongst the hot topics in chemistry. This study describes the synthesis, characterisation as well as catalytic evaluation of unsupported and supported Au NPs....

Magister Scientiae (Medical Bioscience) - MSc(MBS) / Recently nanoparticles (NPs) have been introduced and used in combination with therapeutic approaches to develop nanotechnology-enabled medicine. These nanostructures allow for the exploitation of the physiochemical properties which may be beneficial in cancer treatment. The use of NPs in nanomedicine has proven successful in modern chemotherapeutics and has demonstrated promising potential in in vivo and in vitro radiosensitization studies. This is a baseline study aimed to determine the cytotoxic effects of AuNPs for potential radiosensitization analysis. The study analysed the effects of different AuNP sizes (30, 50 and 80nm), concentrations (5, 10 and 15 μg/ml) over various time periods in CHOK1 and A549 cells. AuNPs were characterised by DLS and ZP analysis and showed that particles were moderately polydispersed and moderately to highly stable in charge. The effects on viability and metabolic activity of cells were determined using crystal violet and the WST-1 assay.

Electrolyte interactions with colloidal nanoparticles (NPs) in aqueous solutions have been implicated in a wide range of research and applications. Existing studies on electrolyte interactions with NPs are primarily based on the electrical double layer (EDL) theory. However, the EDL model provides very limited information on how electrolytes directly bind to NPs, electrolyte impact on charge distribution on NPs, and NP morphological modification upon electrolyte binding. Furthermore, the previous reports have mainly focused on either cations or anions binding onto NPs, while the potential cation and anion coadsorption onto NPs and NPacilitated cation-anion interactions remain largely uncharted. Filling these knowledge gaps are critical to enhance the fundamental understanding of interfacial interactions of electrolytes with NPs. Experimental characterization of cations and anions at the solid/liquid interface is a challenging analytical task. In the first study, we demonstrated the first direct experimental evidence of ion pairing on gold nanoparticles (AuNPs) in water by using surface enhanced Raman spectroscopy (SERS) in combination with electrolyte washing. Unlike ion pairing in aqueous solutions where the oppositely charged ions are either in direct contact or separated by a solvation shell, the ion pairing on AuNPs refers to cation and anion coadsorption onto the same NP surface regardless of separation distance. Ion pairing reduces the electrolyte threshold concentration in inducing AuNP aggregation and enhances the competitiveness of electrolyte over neutral molecules in binding to AuNPs. In the second study, we demonstrated that binding, structure, and properties of an ionic species on AuNPs are significantly dependent on the counterion adsorbed on AuNPs. These counterion effects include electrolyte-induced AuNP aggregation and fusion, quantitative cation and anion coadsorption on AuNPs, and SERS spectral distortion induced by the ionic species on AuNP surfaces. In the final study, we proposed that ion pairing as the main mechanism for reducing electrostatic repulsion among organothiolates self-assembled on AuNPs in water by using a series of experimental and computational studies. The work described in this dissertation provides a series of new insights into electrolyte interfacial interactions with AuNPs.

Gold nanoparticles (AuNPs) have been of interest due to their biocompatibility and surface plasmon resonance. Biomolecules can spontaneously adsorb to their surface, a trait that could be exploited for drug targeting. It is unclear, however, whether protein-AuNP interactions at the nanoparticle surface are dependent on nanoparticle size. In this project, we investigate whether surface curvature can induce protein unfolding and multilayer binding in citrate-coated AuNPs of various sizes. An NMR-based approach was utilized to determine the adsorption capacity, and protein NMR spectra were compared to determine whether nanoparticle size influences protein interactions. Transmission electron microscopy (TEM) was used to support the results. Over a range of AuNP sizes (15-100 nm) proteins appear globular on the nanoparticle surface. Additionally, a single layer of proteins is adsorbed regardless of AuNP size. Our results are consistent for two differently sized proteins, GB3 (6 kDa) and bovine carbonic anhydrase (BCA, 29 kDa).

This dissertation presents the development of an alternative aptamer screening process, Competition-Induced Selection of Ligands (CISL), and its use in screening for ssDNA aptamers for gold substrates. Gold substrates are presented as the nonnucleotide target for implementing CISL as a novel aptamer screening approach. Chapter 1 provides an overview of the in vitro selection of oligonucleotide aptamers, the polymerase chain reaction that is a key step in the aptamer screening process, the synthesis and properties of gold nanoparticles and the biomolecule-mediated formation of inorganic nanoparticles. Chapter 2 presents the goals and objectives of this thesis along with an organizational overview of the dissertation. Chapter 3 describes the experimental techniques and optimizations pertinent to the development of the CISL aptamer screening process. Chapter 4 investigates the effects of various nucleic acid additions during the seed-mediated growth of gold nanoparticles. Chapter 5 discusses the use of CISL in screening for ssDNA aptamer candidates for spherical gold nanoparticles (AuNPs) and the primary and secondary structure analysis of identified sequences. Chapter 6 presents the use of CISL in screening for ssDNA aptamer candidates for planar gold substrates (PlanarAu) and also includes primary and secondary structure analysis of identified sequences accompanied with an incubation study to provide a “frequency” ranking of aptamers as adsorbate species on PlanarAu. Chapter 7 offers concluding remarks and ideas for future expansion and applications of this work.