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Progress towards visualizing the controlled assembly of gold nanoparticles on DNAElmuccio, Michael L. 18 July 2011 (has links)
Our laboratory has used the 1,4,5,8 Naphthalenetetracarboxylic diimine (NDI) unit to develop threading polyintercalators that bind DNA with the NDI units intercalated in between GpG steps and two different peptide linkers, which connect the NDI units, situated in either the major or minor grooves. The first generation bisintercalators, G₃K and [beta]Ala₃K, were shown to bind two different sequences of DNA, where the peptide linkers reside in the major and minor grooves respectively. These binding modules were then combined to generate threading polyintercalators that bound different DNA sequences with simultaneous occupation of both grooves. In particular, a cyclic bisintercalator was designed and DNAse I footprinting revealed a strong preference for the sequence 5'-GGTACC-3'. NMR structural studies of the complex with d(CGGTACCG)₂ verified a pseudocatenane structure in which the NDI units reside four base pairs apart, with one linker located in the minor groove and the other in the major groove. This was the first structurally well-characterized pseudocatenane complex between a sequence-specific cyclic bisintercalator and its preferred binding sequence. The ability to simultaneously occupy both groves of the same sequence is interesting for several reasons. Most significantly, it raises questions about a complex DNA intercalator's ability to locate its preferred sequence within a long strand of DNA. In order to directly assess this, the intercalator was modified (CBI-Cys) to incorporate a gold nanoparticle probe to allow for the direct visualization of the intercalator locating its preferred sequence within a long DNA strand. The appropriate protocols to visualize DNA using electron and atomic force microscopy were unsuccessful; however, the foundation has been set for future work to develop the appropriate method to determine the mechanism by which the cyclic bisintercalator locates its preferred sequence. Additionally, the bisintercalators developed in our laboratory offered a unique opportunity to exploit their sequence specificity for controlled nanoparticle assembly. Over the past decade, nanoparticles and DNA have been used to develop novel nanoparticle assembly systems with the goal of developing electronic devices and nanomaterials. The G₃K bisintercalator was synthetically modified to incorporate a gold nanoparticle probe. This intercalator-nanoparticle conjugate, BisKC·Au, maintained its binding specificity (5'-GGTACC-3') to a modified DNA fragment containing multiple G₃K binding sites. The atomic force microscope has become the most promising tool in visualizing individual DNA molecules. A modified procedure utilized APS to allow for the direct visualizing of plasmid DNA. The framework is now in place to confirm the controlled assembly of the gold nanoparticles. This protocol can then be used for the [beta]Ala₃K bisintercalator to lead to the development of a nanoparticle assembly system that can precisely control the organization of multiple types of nanoparticles. / text
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Near-infrared narrowband imaging of tumors using gold nanoparticlesPuvanakrishnan, Priyaveena 27 January 2012 (has links)
A significant challenge in the surgical resection of tumors is accurate identification of tumor margins. Current methods for margin detection are time-intensive and often result in incomplete tumor excision and recurrence of disease. The objective of this project was to develop a near-infrared narrowband imaging (NIR NBI) system to image tumor and its margins in real-time during surgery utilizing the contrast provided by gold nanoparticles (GNPs). NIR NBI images narrow wavelength bands to enhance contrast from plasmonic particles in a widefield, portable and non-contact device that is clinically compatible for real-time tumor margin demarcation. GNPs have recently gained significant traction as nanovectors for combined imaging and photothermal therapy of tumors. Delivered systemically, GNPs preferentially accumulate at the tumor site via the enhanced permeability and retention effect, and when irradiated with NIR light, produce sufficient heat to treat tumor tissue. The NIR NBI system consists of 1) two LED's: green (530 nm) and NIR (780 nm) LED for illuminating the blood vessels and GNP, respectively, 2) a filter wheel for wavelength selection, and 3) a CCD to collect reflected light from the sample. The NIR NBI system acquires and processes images at a rate of at least 6 frames per second. We have developed custom control software with a graphical user interface that handles both image acquisition and processing/display in real-time. We used mice with a subcutaneous tumor xenograft model that received intravenous administration and topical administration of gold nanoshells and gold nanorods. We determined the GNP's distribution and accumulation pattern within tumors using NIR NBI. Ex vivo NIR NBI of tumor xenografts accumulated with GNPs delivered systemically, demonstrated a highly heterogeneous distribution of GNP within the tumor with higher accumulation at the cortex. GNPs were observed in unique patterns surrounding the perivascular region. The GNPs clearly defined the tumor while surrounding normal tissue did not indicate the presence of particles. In addition, we present results from NBI of tumors that received topical delivery of conjugated GNPs. We determined that tumor labeling using topical delivery approach resulted in a more homogenous distribution of GNPs compared to the systemic delivery approach. Finally, we present results from the on-going in vivo tumor margin imaging studies using NIR NBI. Our results demonstrate the feasibility of NIR NBI in demarcating tumor margins during surgical resection and potentially guiding photo-thermal ablation of tumors. / text
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Enhanced Delivery of Gold Nanoparticles with Therapeutic Potential for Targeting Human Brain TumorsEtame, Arnold 11 December 2012 (has links)
The blood brain barrier (BBB) remains a major challenge to the advancement and application of systemic anti-cancer therapeutics into the central nervous system. The structural and physiological delivery constraints of the BBB significantly limit the effectiveness of conventional chemotherapy, thereby making systemic administration a non-viable option for the vast majority of chemotherapy agents. Furthermore, the lack of specificity of conventional systemic chemotherapy when applied towards malignant brain tumors remains a major shortcoming. Hence novel therapeutic strategies that focus both on targeted and enhanced delivery across the BBB are warranted. In recent years nanoparticles (NPs) have emerged as attractive vehicles for efficient delivery of targeted anti-cancer therapeutics. In particular, gold nanoparticles (AuNPs) have gained prominence in several targeting applications involving systemic cancers. Their enhanced permeation and retention within permissive tumor microvasculature provide a selective advantage for targeting. Malignant brain tumors also exhibit transport-permissive microvasculature secondary to blood brain barrier disruption. Hence AuNPs may have potential relevance for brain tumor targeting. However, the permeation of AuNPs across the BBB has not been well characterized, and hence is a potential limitation for successful application of AuNP-based therapeutics within the central nervous system (CNS).
In this dissertation, we designed and characterized AuNPs and assessed the role of polyethylene glycol (PEG) on the physical and biological properties of AuNPs. We established a size-dependent permeation profile with respect to core size as well as PEG length when AuNPs were assessed through a transport-permissive in-vitro BBB. This study was the first of its kind to systematically examine the influence of design on permeation of AuNPs through transport-permissive BBB. Given the significant delivery limitations through the non-transport permissive and intact BBB, we also assessed the role of magnetic resonance imaging (MRI) guided focused ultrasound (MRgFUS) disruption of the BBB in enhancing permeation of AuNPs across the intact BBB and tumor BBB in vivo. MRgFUS is a novel technique that can transiently increase BBB permeability thereby allowing delivery of therapeutics into the CNS. We demonstrated enhanced delivery of AuNPs with therapeutic potential into the CNS via MRgFUS. Our study was the first to establish a definitive role for MRgFUS in delivering AuNPs into the CNS. In summary, this thesis describes results from a series of research projects that have contributed to our understanding of the influence of design features on AuNP permeation through the BBB and also the potential role of MRgFUS in AuNP permeation across the BBB.
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One-Step Synthesis of Kanamycin Functionalized Gold Nanoparticles With Potent Antibacterial Activity Against Resistant Bacterial StrainsWaghwani, Hitesh Kumar 01 May 2015 (has links)
On the verge of entering the post-antibiotic era, numerous efforts are in place to regain the losing potential of antibiotics which are proving ineffective against common bacterial infections. Engineered nanomaterials, especially gold nanoparticles (GNPs) capped with antibacterial agents are proving to be an effective and novel strategy against multi-drug resistant (MDR) bacteria. In this study, we report a one-step synthesis of kanamycin-capped GNPs (20 ± 5 nm) utilizing the combined reducing and capping ability of the aminoglycoside antibiotic, kanamycin. Antibacterial assays showed dosedependent broad spectrum activity of Kan-GNPs against Gram-positive (Staphylococcus epidermidis and Enterococcus durans), Gram-negative (Escherichia coli and Enterobacter aerogenes) and Kan-resistant and MDR bacterial strains. A significant reduction in the minimum inhibitory concentration (MIC) of Kan-GNPs was observed as compared to free kanamycin against all the sensitive and resistant bacterial strains tested. Mechanistic studies using TEM and fluorescence microscopy showed that Kan- GNPs exerted their bactericidal action through disrupting the cellular membrane resulting in leakage of cytoplasmic content and death of bacterial cells. Results of this study provide a novel method in the development of antibiotic capped GNPs as potent next-generation antibacterial agents.
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Enhanced Delivery of Gold Nanoparticles with Therapeutic Potential for Targeting Human Brain TumorsEtame, Arnold 11 December 2012 (has links)
The blood brain barrier (BBB) remains a major challenge to the advancement and application of systemic anti-cancer therapeutics into the central nervous system. The structural and physiological delivery constraints of the BBB significantly limit the effectiveness of conventional chemotherapy, thereby making systemic administration a non-viable option for the vast majority of chemotherapy agents. Furthermore, the lack of specificity of conventional systemic chemotherapy when applied towards malignant brain tumors remains a major shortcoming. Hence novel therapeutic strategies that focus both on targeted and enhanced delivery across the BBB are warranted. In recent years nanoparticles (NPs) have emerged as attractive vehicles for efficient delivery of targeted anti-cancer therapeutics. In particular, gold nanoparticles (AuNPs) have gained prominence in several targeting applications involving systemic cancers. Their enhanced permeation and retention within permissive tumor microvasculature provide a selective advantage for targeting. Malignant brain tumors also exhibit transport-permissive microvasculature secondary to blood brain barrier disruption. Hence AuNPs may have potential relevance for brain tumor targeting. However, the permeation of AuNPs across the BBB has not been well characterized, and hence is a potential limitation for successful application of AuNP-based therapeutics within the central nervous system (CNS).
In this dissertation, we designed and characterized AuNPs and assessed the role of polyethylene glycol (PEG) on the physical and biological properties of AuNPs. We established a size-dependent permeation profile with respect to core size as well as PEG length when AuNPs were assessed through a transport-permissive in-vitro BBB. This study was the first of its kind to systematically examine the influence of design on permeation of AuNPs through transport-permissive BBB. Given the significant delivery limitations through the non-transport permissive and intact BBB, we also assessed the role of magnetic resonance imaging (MRI) guided focused ultrasound (MRgFUS) disruption of the BBB in enhancing permeation of AuNPs across the intact BBB and tumor BBB in vivo. MRgFUS is a novel technique that can transiently increase BBB permeability thereby allowing delivery of therapeutics into the CNS. We demonstrated enhanced delivery of AuNPs with therapeutic potential into the CNS via MRgFUS. Our study was the first to establish a definitive role for MRgFUS in delivering AuNPs into the CNS. In summary, this thesis describes results from a series of research projects that have contributed to our understanding of the influence of design features on AuNP permeation through the BBB and also the potential role of MRgFUS in AuNP permeation across the BBB.
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Engineering the macro-nano interface : designing the directed self-assembly and interfacial interactions of gold nanoparticle monolayers. /Jespersen, Michael L., January 2007 (has links)
Thesis (Ph. D.)--University of Oregon, 2008. / Typescript. Includes vita and abstract. Includes bibliographical references (leaves 164-192). Also available online in Scholars' Bank; and in ProQuest, free to University of Oregon users.
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A Computational Study to Understand the Surface Reactivity of Gold Nanoparticles with Amines and DNAPong, Boon-Kin, Lee, Jim Yang, Trout, Bernhardt L. 01 1900 (has links)
We conducted a computational adsorption study of methylamine on various surface-models of gold nanoparticle which is facetted by multiple {111} and {100} planes. In addition to these flat surfaces, our models include the stepped surfaces (ridges) formed along the intersections of these planes. Binding on the flat surface was fairly weak, but substantially stronger on the ridges by an average of 4.4 kcal/mol. This finding supports the idea that ssDNA’s interaction with gold nanoparticles occurs through the amines on the purine/pyrrimidine rings. Also, this typically undesirable interaction between DNA and gold nanoparticles is expected to increase as the particle size decreases. Our analysis suggests that particle size is an important controlling parameter to reduce this interaction. / Singapore-MIT Alliance (SMA)
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Síntese de nanopartículas de ouro em solução aquosa, transferência para outros solventes orgânicos e avaliação de sua estabilidade em diferentes meios orgânicosMoreira, Karen Regina Amaro January 2018 (has links)
O objetivo deste estudo foi sintetizar nanopartículas de ouro (AuNPs) em meio aquoso, transferí-las para diferentes meios orgânicos, e avaliar sua estabilidade (não-agregação) nesses meios, com o intuito de otimizar a exploração de suas propriedades ópticas. Foi utilizado o ácido tetracloroáurico (HAuCl4) como precursor de ouro metálico em meio aquoso e fez-se a transferência para clorofórmio (CHCl3) e diclorometano (CH2Cl2). Como agente de transferência, utilizou-se o polietilenoglicol tiolado (PEGSH) junto com o dodecanotiol (DDT). O PEG-SH foi adicionado na fase aquosa para evitar a agregação das AuNPs, assim como em fase orgânica, o DDT foi adicionado como agente estabilizador, pois sua cadeia alifática promove interações hidrofóbicas entre as partículas. Avaliou-se dois diâmetros médios de nanopartículas. A eficiência de transferência e a distribuição de tamanho das AuNPs foram estudadas utilizando a espectroscopia UV-Vis, espalhamento dinâmica de luz e microscopia eletrônica de transmissão. As nanopartículas denominadas AuNPs1 apresentaram AbsRPLS média de 0,8314 em ʎmédio = 521 nm e as AuNPs2 AbsRPLS média de 1,2643 em ʎmédio = 526 nm. Quando as AuNPs foram transferidas para solventes orgânicos, os espectros de absorção obtidos por UV-Vis apresentaram deslocamento da banda RPLS para o vermelho, em CHCl3, ʎAuNPs1 = 531 nm e ʎAuNPs2 = 534 nm; em CH2Cl2, ambas as soluções apresentaram ʎ = 530 nm. Este deslocamento é um dos fatores que indicaram a não-agregação das AuNPs. Em DLS, foi confirmada a nãoagregação. Em CHCl3, as AuNPs1 apresentaram eficiência de transferência de 97,27% e as AuNPs 98,88%, enquanto, em diclorometano, apenas 80,21% das AuNPs foram transferidas. As AuNPs apresentaram ao longo do tempo maior estabilidade em CHCl3 do que em CH2Cl2. Após a transferência para o CHCl3, as AuNPs foram separadas deste solvente e redissolvidas em outros solventes orgânicos com diferentes índices de refração: álcool benzílico, etanol e dimetilsulfóxido (DMSO). As AuNPS permaneceram visivelmente estáveis somente em álcool benzílico, pois nos outros solventes foi observado que a solução coloidal apresentou perda da coloração e por UV-Vis foi verificada a diminuição da banda da RPLS em DMSO e a ausência em etanol. / The objective of this study was to synthesize gold nanoparticles (AuNPs) in aqueous media, transfer them to different organic media, and evaluate their stability (non-aggregation) in these media, in order to optimize the exploration of their optical properties. Tetrachlorouric acid was used as the gold precursor in aqueous medium and transferred to chloroform (CHCl3) and dichloromethane (CH2Cl2). As the transfer agent, thiolated polyethylene glycol (PEG-SH) was used along with dodecanethiol (DDT). PEG-SH was added in the aqueous phase to prevent AuNPs from aggregating, as well as in the organic phase, DDT was added as a stabilizing agent because its aliphatic chain promotes hydrophobic interactions between the particles. Two average nanoparticle diameters were evaluated. The transfer efficiency and size distribution of the AuNPs were studied using UV-Vis spectroscopy, dynamic light scattering and transmission electron microscopy. The nanoparticles named AuNPs1 presented mean AbsRPLS of 0,8314 in ʎmedium = 521 nm and the AuNPs2 AbsLSPR mean of 1,2643 in ʎmedium = 526 nm. When the AuNPs were transferred to organic solvents, the absorption spectra obtained by UV-Vis showed red band shift in CHCl3, ʎAuNPs1 = 531 nm and ʎAuNPs2 = 534 nm; in CH2Cl2, both solutions showed ʎ = 530 nm. This displacement is one of the factors that indicated the non-aggregation of AuNPs. In DLS, non-aggregation was confirmed. In CHCl3, AuNPs1 showed transfer efficiency of 97,27% and AuNPs 98.88%, while in dichloromethane only 80,21% of AuNPs were transferred. AuNPs showed greater stability over time in CHCl3 than in CH2Cl2. After transfer to CHCl3, the AuNPs were separated from this solvent and redissolved in other organic solvents with different refractive indexes: benzyl alcohol, ethanol and dimethylsulfoxide (DMSO). The AuNPS remained visibly stable only in benzyl alcohol, because in the other solvents it was observed that the colloidal solution showed a loss of coloration and, by UV-Vis, the reduction of the LSPR band in DMSO and absence in ethanol was verified.
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Gold Nanoparticles Plasmonic Enhancement for Decoding Of Molecule-Surface InteractionsRondon B., Rebeca A. 01 August 2018 (has links)
In this research, the use of gold nanostructures (AuNS) was explored to evaluate the interaction between molecules and the nanoparticle (NP) surface. In that way, three different projects were developed; one project using fluorescence and two projects using Raman spectroscopy as measuring technique.
The fluorescence spectroscopy project used the fluorescence lifetime imaging microscope (FLIM) to evaluate the relative position of the molecules methylene blue (MB) and cucurbit[7]uril (CB) on the gold nanoparticle (AuNP) surface. Although the inclusion complex is favored in solution, it was found that MB forms an exclusion complex with CB, when CB is attached to the AuNP surface.
The first project utilizing Raman spectroscopy, specifically surface enhanced Raman scattering (SERS), took advantage of a confined system (a reverse micelle) to evaluate the Raman signal of water molecules in close proximity to the AuNP surface. It was observed that the SERS water signal had a big shift to higher energies compared with the Raman signal of the bulk water; indicating the water molecules in the system are subjected to different bond-stretching energies.
The second Raman project studied the modification of two different AuNS (specifically AuNP and gold nanorod -AuNR) with thiols. Different thiols were used to evaluate the kinetics of the modification of the AuNS surface, also the different AuNS presented different ligands on their surface. In general, and considering the difference in the bonding strength of the ligands present on the AuNS surface (by synthesis) and the size of the thiol, at least 2 h are required to modify the complete AuNS surface.
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Development of a Botrytis specific immunosensor : towards using PCR species identificationBinder, Michael January 2014 (has links)
Botrytis species affect over 300 host plants in all climate areas of the world, at both pre and post-harvest stages, leading to significant losses in agricultural produce. Therefore, the development of a rapid, sensitive and reliable method to assess the pathogen load of infected crops can help to prescribe an effective curing regime. Growers would then have the ability to predict and manage the full storage potential of their crops and thus provide an effective disease control and reduce post-harvest losses. A highly sensitive electrochemical immunosensor based on a screen-printed gold electrode (SPGE) with onboard carbon counter and silver / silver chloride (Ag/AgCl) pseudo-reference electrode was developed in this work for the detection and quantification of Botrytis species. The sensor utilised a direct sandwich enzyme-linked immunosorbent assay (ELISA) format with a monoclonal antibody against Botrytis immobilised on the gold working electrode. Two immobilisation strategies were investigated for the capture antibody, and these included adsorption and covalent immobilisation after self-assembled monolayer formation with 3-dithiodipropionic acid (DTDPA). A polyclonal antibody conjugated to the electroactive enzyme horseradish peroxidase (HRP) was then applied for signal generation. Electrochemical measurements were conducted using 3,3’, 5,5’-tetramethylbenzidine dihydrochloride / hydrogen peroxide (TMB/H2O2) as the enzyme substrate system at a potential of -200 mV. The developed biosensor was capable of detecting latent Botrytis infections 24 h post inoculation with a linear range from 150 to 0.05 μg fungal mycelium ml-1 and a limit of detection (LOD) as low as 16 ng ml-1 for covalent immobilisation and 58 ng ml-1 for adsorption, respectively. Benchmarked against the commercially available Botrytis ELISA kits, the optimised immuno-electrochemical biosensor showed strong correlation of the quantified samples (R2=0.998).
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