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• 1. [Article] The Atmosphere can be a Source of Certain Water Soluble Volatile Organic Compounds in Urban Streams

  Surface water and air volatile organic compound (VOC) data from 10 U. S. Geological Survey monitoring sites were used to evaluate the potential for direct transport of VOCs from the atmosphere to urban ...

  Citation × Citation Citation Abstract Copy Title: The Atmosphere can be a Source of Certain Water Soluble Volatile Organic Compounds in Urban Streams Author: Kenner, Scott J, Bender, David A., Pankow, James F., Zogorski, John S. Year: 2014 Surface water and air volatile organic compound (VOC) data from 10 U. S. Geological Survey monitoring sites were used to evaluate the potential for direct transport of VOCs from the atmosphere to urban streams. Analytical results of 87 VOC compounds were screened by evaluating the occurrence and detection levels in both water and air, and equilibrium concentrations in water (C-w(s)) based on the measured air concentrations. Four compounds (acetone, methyl tertiary butyl ether, toluene, and m- & p-xylene) were detected in more than 20% of water samples, in more than 10% of air samples, and more than 10% of detections in air were greater than long-term method detection levels (LTMDL) in water. Benzene was detected in more than 20% of water samples and in more than 10% of air samples. Two percent of benzene detections in air were greater than one-half the LTMDL in water. Six compounds (chloroform, p-isopropyltoluene, methylene chloride, perchloroethene, 1,1,1-trichloroethane, and trichloroethene) were detected in more than 20% of water samples and in more than 10% of air samples. Five VOCs, toluene, m- & p-xylene, methyl tert-butyl ether (MTBE), acetone, and benzene were identified as having sufficiently high concentrations in the atmosphere to be a source to urban streams. MTBE, acetone, and benzene exhibited behavior that was consistent with equilibrium concentrations in the atmosphere. Title: The Atmosphere can be a Source of Certain Water Soluble Volatile Organic Compounds in Urban Streams Author: Kenner, Scott J, Bender, David A., Pankow, James F., Zogorski, John S. Year: 2014 Surface water and air volatile organic compound (VOC) data from 10 U. S. Geological Survey monitoring sites were used to evaluate the potential for direct transport of VOCs from the atmosphere to urban streams. Analytical results of 87 VOC compounds were screened by evaluating the occurrence and detection levels in both water and air, and equilibrium concentrations in water (C-w(s)) based on the measured air concentrations. Four compounds (acetone, methyl tertiary butyl ether, toluene, and m- & p-xylene) were detected in more than 20% of water samples, in more than 10% of air samples, and more than 10% of detections in air were greater than long-term method detection levels (LTMDL) in water. Benzene was detected in more than 20% of water samples and in more than 10% of air samples. Two percent of benzene detections in air were greater than one-half the LTMDL in water. Six compounds (chloroform, p-isopropyltoluene, methylene chloride, perchloroethene, 1,1,1-trichloroethane, and trichloroethene) were detected in more than 20% of water samples and in more than 10% of air samples. Five VOCs, toluene, m- & p-xylene, methyl tert-butyl ether (MTBE), acetone, and benzene were identified as having sufficiently high concentrations in the atmosphere to be a source to urban streams. MTBE, acetone, and benzene exhibited behavior that was consistent with equilibrium concentrations in the atmosphere. Close

• 2. [Article] Vibrational Sum Frequency Spectroscopic Investigations of Sulfur Dioxide Adsorption to Atmospherically Relevant Aqueous Surfaces

  xv, 108 p. : ill. (chiefly col.)

  Citation × Citation Citation Abstract Copy Title: Vibrational Sum Frequency Spectroscopic Investigations of Sulfur Dioxide Adsorption to Atmospherically Relevant Aqueous Surfaces Author: Ota, Stephanie Tomoko, 1978- Year: 2011 xv, 108 p. : ill. (chiefly col.) Title: Vibrational Sum Frequency Spectroscopic Investigations of Sulfur Dioxide Adsorption to Atmospherically Relevant Aqueous Surfaces Author: Ota, Stephanie Tomoko, 1978- Year: 2011 xv, 108 p. : ill. (chiefly col.) Close

• 3. [Article] In situ analysis of aqueous structure and adsorption at fluorocarbon, hydrocarbon and mineral surfaces

  xvii, 209 p. : ill. A print copy of this thesis is available through the UO Libraries. Search the library catalog for the location and call number.

  Citation × Citation Citation Abstract Copy Title: In situ analysis of aqueous structure and adsorption at fluorocarbon, hydrocarbon and mineral surfaces Author: Hopkins, Adam Justin, 1980- Year: 2011, 2010 xvii, 209 p. : ill. A print copy of this thesis is available through the UO Libraries. Search the library catalog for the location and call number. Title: In situ analysis of aqueous structure and adsorption at fluorocarbon, hydrocarbon and mineral surfaces Author: Hopkins, Adam Justin, 1980- Year: 2011, 2010 xvii, 209 p. : ill. A print copy of this thesis is available through the UO Libraries. Search the library catalog for the location and call number. Close

• 4. [Article] A Method to Derivatize Surface Silanol Groups to Si-Alkyl Groups in Carbon-Doped Silicon Oxides

  A carbon-doped silicon oxide (CDO) finds use as a material with a low dielectric constant (k) for copper interconnects in multilayered integrated circuits (ICs). Hydrophilic silanol groups (Si–OH) on its ...

  Citation × Citation Citation Abstract Copy Title: A Method to Derivatize Surface Silanol Groups to Si-Alkyl Groups in Carbon-Doped Silicon Oxides Author: Darmakkolla, Srikar Rao, Tran, Hoang, Gupta, Atul, Rananavare, Shankar B. Year: 2016 A carbon-doped silicon oxide (CDO) finds use as a material with a low dielectric constant (k) for copper interconnects in multilayered integrated circuits (ICs). Hydrophilic silanol groups (Si–OH) on its surface, however, can attract moisture, thereby causing an undesirable increase in the dielectric constant. Modification of the exposed hydrophilic surface to a hydrophobic functional group provides one solution to this problem. We report here a strategy for converting surface Si–OH to hydrophobic silicon hydride (Si–H) without affecting the internal oxide network in CDO. The approach involves esterification of the exposed silanol to its triflate (silyltrifluoromethanesulfonate, Si–O–Tf), followed by reduction to Si–H with diisobutylaluminum hydride. Si–H is further modified by a photochemical reaction with an alkene (1-octadecene) to yield Si–R (R = –C18H37) to provide a more moisture resistant, and less polar Si–C as opposed to the Si–O backbone. Fourier transform infrared (FT-IR) spectroscopy, X-ray photoelectron spectrometry (XPS), and measurements of the contact angle with water substantiated the successful conversion. The reaction scheme is versatile, transforming silanol groups to silicon hydride in widely varying chemical sites, from small molecules to the surfaces of silica gels, SiOx and CDO wafers. A comparison with the films (self-assembled monolayers) derivatized with the octadecyltrichlorosilane indicated that the new method leads to a thicker (≈5 nm) but more loosely packed hydrocarbon film with slightly lower contact angles. Title: A Method to Derivatize Surface Silanol Groups to Si-Alkyl Groups in Carbon-Doped Silicon Oxides Author: Darmakkolla, Srikar Rao, Tran, Hoang, Gupta, Atul, Rananavare, Shankar B. Year: 2016 A carbon-doped silicon oxide (CDO) finds use as a material with a low dielectric constant (k) for copper interconnects in multilayered integrated circuits (ICs). Hydrophilic silanol groups (Si–OH) on its surface, however, can attract moisture, thereby causing an undesirable increase in the dielectric constant. Modification of the exposed hydrophilic surface to a hydrophobic functional group provides one solution to this problem. We report here a strategy for converting surface Si–OH to hydrophobic silicon hydride (Si–H) without affecting the internal oxide network in CDO. The approach involves esterification of the exposed silanol to its triflate (silyltrifluoromethanesulfonate, Si–O–Tf), followed by reduction to Si–H with diisobutylaluminum hydride. Si–H is further modified by a photochemical reaction with an alkene (1-octadecene) to yield Si–R (R = –C18H37) to provide a more moisture resistant, and less polar Si–C as opposed to the Si–O backbone. Fourier transform infrared (FT-IR) spectroscopy, X-ray photoelectron spectrometry (XPS), and measurements of the contact angle with water substantiated the successful conversion. The reaction scheme is versatile, transforming silanol groups to silicon hydride in widely varying chemical sites, from small molecules to the surfaces of silica gels, SiOx and CDO wafers. A comparison with the films (self-assembled monolayers) derivatized with the octadecyltrichlorosilane indicated that the new method leads to a thicker (≈5 nm) but more loosely packed hydrocarbon film with slightly lower contact angles. Close

• 5. [Article] Hydrophobic Surfactant Proteins Strongly Induce Negative Curvature

  The hydrophobic surfactant proteins SP-B and SP-C greatly accelerate the adsorption of vesicles containing the surfactant lipids to form a film that lowers the surface tension of the air/water interface ...

  Citation × Citation Citation Abstract Copy Title: Hydrophobic Surfactant Proteins Strongly Induce Negative Curvature Author: Chavarha, Mariya, Loney, Ryan W., Rananavare, Shankar B., Hall, Stephen B. Year: 2015 The hydrophobic surfactant proteins SP-B and SP-C greatly accelerate the adsorption of vesicles containing the surfactant lipids to form a film that lowers the surface tension of the air/water interface in the lungs. Pulmonary surfactant enters the interface by a process analogous to the fusion of two vesicles. As with fusion, several factors affect adsorption according to how they alter the curvature of lipid leaflets, suggesting that adsorption proceeds via a rate-limiting structure with negative curvature, in which the hydrophilic face of the phospholipid leaflets is concave. In the studies reported here, we tested whether the surfactant proteins might promote adsorption by inducing lipids to adopt a more negative curvature, closer to the configuration of the hypothetical intermediate. Our experiments used x-ray diffraction to determine how the proteins in their physiological ratio affect the radius of cylindrical monolayers in the negatively curved, inverse hexagonal phase. With binary mixtures of dioleoylphosphatidylethanolamine (DOPE) and dioleoylphosphatidylcholine (DOPC), the proteins produced a dose-related effect on curvature that depended on the phospholipid composition. With DOPE alone, the proteins produced no change. With an increasing mol fraction of DOPC, the response to the proteins increased, reaching a maximum 50% reduction in cylindrical radius at 5% (w/w) protein. This change represented a doubling of curvature at the outer cylindrical surface. The change in spontaneous curvature, defined at approximately the level of the glycerol group, would be greater. Analysis of the results in terms of a Langmuir model for binding to a surface suggests that the effect of the lipids is consistent with a change in the maximum binding capacity. Our findings show that surfactant proteins can promote negative curvature, and support the possibility that they facilitate adsorption by that mechanism. Title: Hydrophobic Surfactant Proteins Strongly Induce Negative Curvature Author: Chavarha, Mariya, Loney, Ryan W., Rananavare, Shankar B., Hall, Stephen B. Year: 2015 The hydrophobic surfactant proteins SP-B and SP-C greatly accelerate the adsorption of vesicles containing the surfactant lipids to form a film that lowers the surface tension of the air/water interface in the lungs. Pulmonary surfactant enters the interface by a process analogous to the fusion of two vesicles. As with fusion, several factors affect adsorption according to how they alter the curvature of lipid leaflets, suggesting that adsorption proceeds via a rate-limiting structure with negative curvature, in which the hydrophilic face of the phospholipid leaflets is concave. In the studies reported here, we tested whether the surfactant proteins might promote adsorption by inducing lipids to adopt a more negative curvature, closer to the configuration of the hypothetical intermediate. Our experiments used x-ray diffraction to determine how the proteins in their physiological ratio affect the radius of cylindrical monolayers in the negatively curved, inverse hexagonal phase. With binary mixtures of dioleoylphosphatidylethanolamine (DOPE) and dioleoylphosphatidylcholine (DOPC), the proteins produced a dose-related effect on curvature that depended on the phospholipid composition. With DOPE alone, the proteins produced no change. With an increasing mol fraction of DOPC, the response to the proteins increased, reaching a maximum 50% reduction in cylindrical radius at 5% (w/w) protein. This change represented a doubling of curvature at the outer cylindrical surface. The change in spontaneous curvature, defined at approximately the level of the glycerol group, would be greater. Analysis of the results in terms of a Langmuir model for binding to a surface suggests that the effect of the lipids is consistent with a change in the maximum binding capacity. Our findings show that surfactant proteins can promote negative curvature, and support the possibility that they facilitate adsorption by that mechanism. Close

• 6. [Article] Aqueous Red-Emitting Silicon Nanoparticles for Cellular Imaging: Consequences of Protecting Against Surface Passivation by Hydroxide and Water for Stable Red Emission

  Stable, aqueous, red-to-near infrared emission is critical for the use of silicon nanoparticles (Si NPs) in biological fluorescence assays, but such Si NPs have been difficult to attain. We report a synthesis ...

  Citation × Citation Citation Abstract Copy Title: Aqueous Red-Emitting Silicon Nanoparticles for Cellular Imaging: Consequences of Protecting Against Surface Passivation by Hydroxide and Water for Stable Red Emission Author: Chiu, Sheng-Kuei, Manhat, Beth Ann, DeBenedetti, William J.I., Brown, Anna L., Fichter, Katye, Vu, Tania, Eastman, Micah, Jiao, Jun, Goforth, Andrea Mitchell Year: 2013 Stable, aqueous, red-to-near infrared emission is critical for the use of silicon nanoparticles (Si NPs) in biological fluorescence assays, but such Si NPs have been difficult to attain. We report a synthesis and surface modification strategy that protects Si NPs and preserves red photoluminescence (PL) in water for more than 6 mo. The Si NPs were synthesized via high temperature reaction, liberated from an oxide matrix, and functionalized via hydrosilylation to yield hydrophobic particles. The hydrophobic Si NPs were phase transferred to water using the surfactant cetyltrimethylammonium bromide (CTAB) with retention of red PL. CTAB apparently serves a double role in providing stable, aqueous, red-emitting Si NPs by (i) forming a hydrophobic barrier between the Si NPs and water and (ii) providing aqueous colloidal stability via the polar head group. We demonstrate preservation of the aqueous red emission of these Si NPs in biological media and examine the effects of pH on emission color. Title: Aqueous Red-Emitting Silicon Nanoparticles for Cellular Imaging: Consequences of Protecting Against Surface Passivation by Hydroxide and Water for Stable Red Emission Author: Chiu, Sheng-Kuei, Manhat, Beth Ann, DeBenedetti, William J.I., Brown, Anna L., Fichter, Katye, Vu, Tania, Eastman, Micah, Jiao, Jun, Goforth, Andrea Mitchell Year: 2013 Stable, aqueous, red-to-near infrared emission is critical for the use of silicon nanoparticles (Si NPs) in biological fluorescence assays, but such Si NPs have been difficult to attain. We report a synthesis and surface modification strategy that protects Si NPs and preserves red photoluminescence (PL) in water for more than 6 mo. The Si NPs were synthesized via high temperature reaction, liberated from an oxide matrix, and functionalized via hydrosilylation to yield hydrophobic particles. The hydrophobic Si NPs were phase transferred to water using the surfactant cetyltrimethylammonium bromide (CTAB) with retention of red PL. CTAB apparently serves a double role in providing stable, aqueous, red-emitting Si NPs by (i) forming a hydrophobic barrier between the Si NPs and water and (ii) providing aqueous colloidal stability via the polar head group. We demonstrate preservation of the aqueous red emission of these Si NPs in biological media and examine the effects of pH on emission color. Close

• 7. [Article] Minimizing Corrosion of Outdoor Metalworks Using Dispersed Chemically Stabilized Nanoclays in Polyvinylidene Fluoride Latex Coatings

  Nanoclays are small enough to appear optically transparent, yet they have large surface-to-volume and high aspect ratios that can significantly inhibit water diffusion when incorporated into protective ...

  Citation × Citation Citation Abstract Copy Title: Minimizing Corrosion of Outdoor Metalworks Using Dispersed Chemically Stabilized Nanoclays in Polyvinylidene Fluoride Latex Coatings Author: Swartz, Natasja Alexandria, Price, Capri A., Clare, Tami Lasseter Year: 2016 Nanoclays are small enough to appear optically transparent, yet they have large surface-to-volume and high aspect ratios that can significantly inhibit water diffusion when incorporated into protective coatings. Clear coatings, which minimally affect the aesthetics of metalworks, are commonly applied to outdoor metalworks, such as sculptures, to prevent and slow corrosion. In recent years, waterborne clear coatings, rather than solvent-based clear coatings, are increasingly used in many applications to reduce the quantity of volatile organic components in the formulation, yet the performance of dry films produced from waterborne colloidal suspensions is generally poorer. In this work, we aim to improve the barrier properties of a highly weatherable waterborne acrylic/polyvinylidene fluoride emulsion by adding a synthetic nanoclay, Laponite, into the formulation. To improve clay−polymer compatibility, the clay was covalently modified using an acetoxy or perfluoroalkyl silane monomer that is reactive with the hydroxyl groups at the edges of the Laponite platelets. Cation exchange on the clay faces using phosphorylcholine was conducted to increase the stability in water and characterized by zeta potential. Resulting changes in barrier properties of the polymer nanocomposite films were characterized by gravimetry, colorimetry, and electrochemical impedance spectroscopy. Surface ablation after accelerated artificial weathering was monitored by attenuated total internal reflectance Fourier transform infrared microspectroscopy and Raman microspectroscopy, thin film X-ray diffraction (TF-XRD) and gloss and thickness measurements. The composite films showed many improved properties: reduced water sensitivity and ultraviolet-induced polymer degradation, which increased the barrier properties and reduced the diffusion constants over both short- and long-term weathering studies compared with films without nanoclays. The diffusion constant measured for the highest performing composite film showed that the performance gap between relevant water- and solvent-borne coatings used to protect outdoor metals was narrowed by half. Title: Minimizing Corrosion of Outdoor Metalworks Using Dispersed Chemically Stabilized Nanoclays in Polyvinylidene Fluoride Latex Coatings Author: Swartz, Natasja Alexandria, Price, Capri A., Clare, Tami Lasseter Year: 2016 Nanoclays are small enough to appear optically transparent, yet they have large surface-to-volume and high aspect ratios that can significantly inhibit water diffusion when incorporated into protective coatings. Clear coatings, which minimally affect the aesthetics of metalworks, are commonly applied to outdoor metalworks, such as sculptures, to prevent and slow corrosion. In recent years, waterborne clear coatings, rather than solvent-based clear coatings, are increasingly used in many applications to reduce the quantity of volatile organic components in the formulation, yet the performance of dry films produced from waterborne colloidal suspensions is generally poorer. In this work, we aim to improve the barrier properties of a highly weatherable waterborne acrylic/polyvinylidene fluoride emulsion by adding a synthetic nanoclay, Laponite, into the formulation. To improve clay−polymer compatibility, the clay was covalently modified using an acetoxy or perfluoroalkyl silane monomer that is reactive with the hydroxyl groups at the edges of the Laponite platelets. Cation exchange on the clay faces using phosphorylcholine was conducted to increase the stability in water and characterized by zeta potential. Resulting changes in barrier properties of the polymer nanocomposite films were characterized by gravimetry, colorimetry, and electrochemical impedance spectroscopy. Surface ablation after accelerated artificial weathering was monitored by attenuated total internal reflectance Fourier transform infrared microspectroscopy and Raman microspectroscopy, thin film X-ray diffraction (TF-XRD) and gloss and thickness measurements. The composite films showed many improved properties: reduced water sensitivity and ultraviolet-induced polymer degradation, which increased the barrier properties and reduced the diffusion constants over both short- and long-term weathering studies compared with films without nanoclays. The diffusion constant measured for the highest performing composite film showed that the performance gap between relevant water- and solvent-borne coatings used to protect outdoor metals was narrowed by half. Close

• 8. [Article] Effects of Gramicidin-A on the Adsorption of Phospholipids to the Air–Water Interface

  Prior studies suggest that the hydrophobic surfactant proteins, SP-B and SP-C, promote adsorption of the lipids in pulmonary surfactant to an air–water interface by stabilizing a negatively curved rate-limiting ...

  Citation × Citation Citation Abstract Copy Title: Effects of Gramicidin-A on the Adsorption of Phospholipids to the Air–Water Interface Author: Biswas, Samares C., Rananavare, Shankar B., Hall, Stephen B. Year: 2005 Prior studies suggest that the hydrophobic surfactant proteins, SP-B and SP-C, promote adsorption of the lipids in pulmonary surfactant to an air–water interface by stabilizing a negatively curved rate-limiting structure that is intermediate between bilayer vesicles and the surface film. This model predicts that other peptides capable of stabilizing negative curvature should also promote lipid adsorption. Previous reports have shown that under appropriate conditions, gramicidin-A (GrA) induces dioleoyl phosphatidylcholine (DOPC), but not dimyristoyl phosphatidylcholine (DMPC), to form the negatively curved hexagonal-II (HII) phase. The studies reported here determined if GrA would produce the same effects on adsorption of DMPC and DOPC that the hydrophobic surfactant proteins have on the surfactant lipids. Small angle X-ray scattering and 31P-nuclear magnetic resonance confirmed that at the particular conditions used to study adsorption, GrA induced DOPC to form the HII phase, but DMPC remained lamellar. Measurements of surface tension showed that GrA in vesicles produced a general increase in the rate of adsorption for both phospholipids. When restricted to the interface, however, in preexisting films, GrA with DOPC, but not with DMPC, replicated the ability of the surfactant proteins to promote adsorption of vesicles containing only the lipids. The correlation between the structural and functional effects of GrA with the two phospholipids, and the similar effects on adsorption of GrA with DOPC and the hydrophobic surfactant proteins with the surfactant lipids fit with the model in which SP-B and SP-C facilitate adsorption by stabilizing a rate-limiting intermediate with negative curvature. Title: Effects of Gramicidin-A on the Adsorption of Phospholipids to the Air–Water Interface Author: Biswas, Samares C., Rananavare, Shankar B., Hall, Stephen B. Year: 2005 Prior studies suggest that the hydrophobic surfactant proteins, SP-B and SP-C, promote adsorption of the lipids in pulmonary surfactant to an air–water interface by stabilizing a negatively curved rate-limiting structure that is intermediate between bilayer vesicles and the surface film. This model predicts that other peptides capable of stabilizing negative curvature should also promote lipid adsorption. Previous reports have shown that under appropriate conditions, gramicidin-A (GrA) induces dioleoyl phosphatidylcholine (DOPC), but not dimyristoyl phosphatidylcholine (DMPC), to form the negatively curved hexagonal-II (HII) phase. The studies reported here determined if GrA would produce the same effects on adsorption of DMPC and DOPC that the hydrophobic surfactant proteins have on the surfactant lipids. Small angle X-ray scattering and 31P-nuclear magnetic resonance confirmed that at the particular conditions used to study adsorption, GrA induced DOPC to form the HII phase, but DMPC remained lamellar. Measurements of surface tension showed that GrA in vesicles produced a general increase in the rate of adsorption for both phospholipids. When restricted to the interface, however, in preexisting films, GrA with DOPC, but not with DMPC, replicated the ability of the surfactant proteins to promote adsorption of vesicles containing only the lipids. The correlation between the structural and functional effects of GrA with the two phospholipids, and the similar effects on adsorption of GrA with DOPC and the hydrophobic surfactant proteins with the surfactant lipids fit with the model in which SP-B and SP-C facilitate adsorption by stabilizing a rate-limiting intermediate with negative curvature. Close

• 9. [Article] Don Juan Pond, Antarctica: Near-surface CaCl2-brine feeding Earth’s most saline lake and implications for Mars

  To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf. The published article is copyrighted by Nature ...

  Citation × Citation Citation Abstract Copy Title: Don Juan Pond, Antarctica: Near-surface CaCl2-brine feeding Earth’s most saline lake and implications for Mars Author: Dickson, James L., Marchant, David R., Head, James W., Levy, Joseph S. To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf. The published article is copyrighted by Nature Publishing Group and can be found at: http://www.nature.com/. Title: Don Juan Pond, Antarctica: Near-surface CaCl2-brine feeding Earth’s most saline lake and implications for Mars Author: Dickson, James L., Marchant, David R., Head, James W., Levy, Joseph S. To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf. The published article is copyrighted by Nature Publishing Group and can be found at: http://www.nature.com/. Close

• 10. [Article] Expanding the Versatility of Nano Assembled Capsules as Platform of Potential High Payload MRI Contrast Agents

  Magnetic resonance imaging (MRI) has become a powerful clinical modality in diagnostic medicine. It is non-invasive and offers high spatial and temporal resolution. The goal of molecular imaging is to ...

  Citation × Citation Citation Abstract Copy Title: Expanding the Versatility of Nano Assembled Capsules as Platform of Potential High Payload MRI Contrast Agents Author: Farashishiko, Annah Year: 2016 Magnetic resonance imaging (MRI) has become a powerful clinical modality in diagnostic medicine. It is non-invasive and offers high spatial and temporal resolution. The goal of molecular imaging is to reveal the pathophysiology underlying the observed anatomy and diagnose diseases. The detection of pathological biomarkers can lead to early recognition of diseases and improved monitoring for recurrence. Clinically available contrast agents are limited in their discrimination of contrast between tissues and they tend to have very high detection limits. Because biomarkers are very low in concentration there is a need for high payload deposition of contrast agent (CA) and targeted imaging. Encapsulating discrete Gd3+ chelates in nano assembled capsules (NACs) is a simple and effective method of preparing an MRI contrast agent capable of delivering a large payload of high relaxivity imaging agent. The preparation of contrast agent containing NACs had previously focused on preparations incorporating GdDOTP5- into the internal aggregate. In this report we demonstrate that other Gd3+ chelates bearing overall charges as low as 2- can also be used to prepare NACs. This discovery opens up the possibility of using Gd3+ chelates that have inner-sphere water molecules that could further increase the relaxivity enhancement associated with the long rotational correlation time (TR) that arises from encapsulation. However, encapsulation of the q = 1 chelate GdDTPA2- afforded the same increase in relaxivity as the outer-sphere chelate GdTTHA3-. This leads us to the conclusion that in the NAC interior proton transport is not mediated by movement of whole water molecules and the enhanced relaxivity of Gd3+ chelate encapsulated within NACs arises primarily from second sphere effects. The nano assembled capsule platform has been further expanded by an alternative coating method, a new cross linked peptidic shell reported in this work affords robust capsules and exceptionally high per Gd3+ relaxivities (70.7 mM-1s-1). The availability of free amines on the surface of these capsules can be exploited to attach targeting moieties. This was demonstrated through the reaction of fluorescein isothiocyanate (FITC), an intense green emitting dye, with these amines. Green emission from the capsules indicated that surface amines were accessible to FITC. Unlike T1-shortening contrast agents, paraCEST agents can be switched on and off by the imaging scientist by turning on and off a pre-saturation pulse. This affords the ability to acquire both pre- and post-contrast images even after administration of a paraCEST contrast agent. This could potentially eliminate problems co-registering pre- and post-contrast images. A reverse NAC may allow a cationic paraCEST contrast agent to be incorporated in a high payload NAC. We were successful in synthesizing a reverse capsule using DyDOTAM3+, a paraCEST agent, and the negatively charged polymer polyacrylate and encapsulated with SiO2 nanoparticles. These initial preparations of reverse NACs were not able to generate CEST contrast however. Title: Expanding the Versatility of Nano Assembled Capsules as Platform of Potential High Payload MRI Contrast Agents Author: Farashishiko, Annah Year: 2016 Magnetic resonance imaging (MRI) has become a powerful clinical modality in diagnostic medicine. It is non-invasive and offers high spatial and temporal resolution. The goal of molecular imaging is to reveal the pathophysiology underlying the observed anatomy and diagnose diseases. The detection of pathological biomarkers can lead to early recognition of diseases and improved monitoring for recurrence. Clinically available contrast agents are limited in their discrimination of contrast between tissues and they tend to have very high detection limits. Because biomarkers are very low in concentration there is a need for high payload deposition of contrast agent (CA) and targeted imaging. Encapsulating discrete Gd3+ chelates in nano assembled capsules (NACs) is a simple and effective method of preparing an MRI contrast agent capable of delivering a large payload of high relaxivity imaging agent. The preparation of contrast agent containing NACs had previously focused on preparations incorporating GdDOTP5- into the internal aggregate. In this report we demonstrate that other Gd3+ chelates bearing overall charges as low as 2- can also be used to prepare NACs. This discovery opens up the possibility of using Gd3+ chelates that have inner-sphere water molecules that could further increase the relaxivity enhancement associated with the long rotational correlation time (TR) that arises from encapsulation. However, encapsulation of the q = 1 chelate GdDTPA2- afforded the same increase in relaxivity as the outer-sphere chelate GdTTHA3-. This leads us to the conclusion that in the NAC interior proton transport is not mediated by movement of whole water molecules and the enhanced relaxivity of Gd3+ chelate encapsulated within NACs arises primarily from second sphere effects. The nano assembled capsule platform has been further expanded by an alternative coating method, a new cross linked peptidic shell reported in this work affords robust capsules and exceptionally high per Gd3+ relaxivities (70.7 mM-1s-1). The availability of free amines on the surface of these capsules can be exploited to attach targeting moieties. This was demonstrated through the reaction of fluorescein isothiocyanate (FITC), an intense green emitting dye, with these amines. Green emission from the capsules indicated that surface amines were accessible to FITC. Unlike T1-shortening contrast agents, paraCEST agents can be switched on and off by the imaging scientist by turning on and off a pre-saturation pulse. This affords the ability to acquire both pre- and post-contrast images even after administration of a paraCEST contrast agent. This could potentially eliminate problems co-registering pre- and post-contrast images. A reverse NAC may allow a cationic paraCEST contrast agent to be incorporated in a high payload NAC. We were successful in synthesizing a reverse capsule using DyDOTAM3+, a paraCEST agent, and the negatively charged polymer polyacrylate and encapsulated with SiO2 nanoparticles. These initial preparations of reverse NACs were not able to generate CEST contrast however. Close