Engineered nanomaterials (ENMs) have significant commercial potential in a broad range of industr... more Engineered nanomaterials (ENMs) have significant commercial potential in a broad range of industries for consumer products as a result of their novel properties. However, these same properties may cause unexpected risks once ENMs are released into the environment either intentionally or unintentionally. Thus, standard methods are needed to accurately and reproducibly assess the potential risk of ENMs. One factor that limits the applicability of standard ecotoxicology test methods for use with ENMs is that the unique behaviors of ENMs may cause artifacts or misinterpretations in these tests as a result of their unique behaviors. We briefly discuss these artifacts and misinterpretations and provide an illustrative example.
Acrylic-acid based polyelectrolytes are used for dispersion and rheology control of ceramic powde... more Acrylic-acid based polyelectrolytes are used for dispersion and rheology control of ceramic powder slips. This study focuses on the Si{sub 3}N4/H{sub 2}O/poly(acrylic acid) (PAA) system, with the goal of improving our basic understanding of the mechanisms which may significantly affect slip properties during processing. A variety of experimental techniques were employed, including potentiometric titration, electroacoustic analysis, adsorption isotherms, and controlled-stress rheology. The slips exhibited complex behavior over a wide range of conditions in which solids concentration, PAA molecular weight and concentration, and pH were varied. Polymer charge and conformation were found to have significant impact on the flow properties. Pseudoplastic behavior was attributed to the presence of free polymer. The flow properties were also found to be highly pH dependent.
Nanoparticles (NPs) are known to interfere with many high-throughput cell viability and cell prol... more Nanoparticles (NPs) are known to interfere with many high-throughput cell viability and cell proliferation assays, which complicates the assessment of their potential toxic effects. The aim of this study was to compare viability and proliferation results for colloidal silica (SiO2 NP; 7 nm) in the RAW 264.7 mouse macrophage cell line using three different techniques: plate-based assays, flow cytometry analysis, and Coulter counter assays. Our data indicate that CellTiter-Blue, XTT, and CyQuant plate-based assays show increased values over control at low SiO2 NPs concentrations (0.001–0.01 g/L). SiO2 NPs show little-to-no interference with flow cytometry and Coulter counter assays, which not only were more reliable in determining cell viability and proliferation at low concentrations in vitro, but also identified changes in cell granularity and size that were not captured by the plate-based assays. At high SiO2 NP concentrations (1 g/L) all techniques indicated cytotoxicity. In concl...
ABSTRACT Most structural ceramics are manufactured using powders as starting materials. Since int... more ABSTRACT Most structural ceramics are manufactured using powders as starting materials. Since intelligent processing of powders and slurries is one of the vehicles to achieve improved manufacturing of ceramics, a consortium has been initiated at NIST to develop some of the necessary tools. The primary goal of this consortium is to develop improved surface chemical understanding of aqueous slurry processing with a focus on electroacoustics and nuclear magnetic resonance (NMR) techniques. Recent developments in electroacoustics have made it possible to carry out interface chemistry and agglomerate size distribution measurements in dense suspensions, thus making this technique uniquely suitable for online measurements. Underlying reasons for selecting these techniques and status of technical developments in their application are presented.
The adsorption of polyelectrolytes and nanoparticles onto patterned and curved surfaces is invest... more The adsorption of polyelectrolytes and nanoparticles onto patterned and curved surfaces is investigated (by fluorescence and electron microscopy) and exploited to produce anisotropic patchy particles. Various anisotropic properties are necessary for the self-assembly of complex structures. In this work, particles were bound temporarily to a substrate, so that part of their surfaces is occluded during subsequent surface modification by the
Intact liposome-based targeted nanoparticle delivery systems (NDS) are immobilized by non-selecti... more Intact liposome-based targeted nanoparticle delivery systems (NDS) are immobilized by non-selective binding and characterized by scanning probe microscopy (SPM) in a fluid imaging environment. The size, size distribution, functionality, and stability of an NDS with a payload consisting of a super-paramagnetic iron oxide contrast agent for magnetic resonance imaging are determined. SPM results are combined with information obtained by more familiar techniques such as superconducting quantum interference device (SQUID) magnetometry, dynamic light scattering, and electron microscopy. By integrating the methods presented in this work into the NDS formulation and manufacturing process, size-dependent statistical properties of the complex can be obtained and the structure-function relationship of individual, multi-component nanoscale entities can be assessed in a reliable and reproducible manner.
Synthetic surfactants are widely used in emulsion polymerization, but it is increasingly desirabl... more Synthetic surfactants are widely used in emulsion polymerization, but it is increasingly desirable to replace them with naturally derived molecules with a reduced environmental burden. This study demonstrates the use of saponins as biodegradable and renewable surfactants for emulsion polymerization. This chemical has been extracted from soapnuts by microwave assisted extraction and characterized in terms of surfactant properties prior to emulsion polymerization. The results in terms of particle size distribution and morphology control have been compared to those obtained with classical nonionic (NP40) or anionic (SDS) industrial surfactants. Microwave-extracted saponins were able to lead to latexes as stable as standard PS latex, as shown by the CMC and CCC measurements. The saponin-stabilized PS particles have been characterized in terms of particle size and distribution by Dynamic Light Scattering and Asymmetrical Flow Field Flow Fractionation. Monomodal and monodispersed particles ranging from 250 to 480 nm in terms of diameter with a particle size distribution below 1.03 have been synthesized.
Engineered nanomaterials (ENMs) have significant commercial potential in a broad range of industr... more Engineered nanomaterials (ENMs) have significant commercial potential in a broad range of industries for consumer products as a result of their novel properties. However, these same properties may cause unexpected risks once ENMs are released into the environment either intentionally or unintentionally. Thus, standard methods are needed to accurately and reproducibly assess the potential risk of ENMs. One factor that limits the applicability of standard ecotoxicology test methods for use with ENMs is that the unique behaviors of ENMs may cause artifacts or misinterpretations in these tests as a result of their unique behaviors. We briefly discuss these artifacts and misinterpretations and provide an illustrative example.
Acrylic-acid based polyelectrolytes are used for dispersion and rheology control of ceramic powde... more Acrylic-acid based polyelectrolytes are used for dispersion and rheology control of ceramic powder slips. This study focuses on the Si{sub 3}N4/H{sub 2}O/poly(acrylic acid) (PAA) system, with the goal of improving our basic understanding of the mechanisms which may significantly affect slip properties during processing. A variety of experimental techniques were employed, including potentiometric titration, electroacoustic analysis, adsorption isotherms, and controlled-stress rheology. The slips exhibited complex behavior over a wide range of conditions in which solids concentration, PAA molecular weight and concentration, and pH were varied. Polymer charge and conformation were found to have significant impact on the flow properties. Pseudoplastic behavior was attributed to the presence of free polymer. The flow properties were also found to be highly pH dependent.
Nanoparticles (NPs) are known to interfere with many high-throughput cell viability and cell prol... more Nanoparticles (NPs) are known to interfere with many high-throughput cell viability and cell proliferation assays, which complicates the assessment of their potential toxic effects. The aim of this study was to compare viability and proliferation results for colloidal silica (SiO2 NP; 7 nm) in the RAW 264.7 mouse macrophage cell line using three different techniques: plate-based assays, flow cytometry analysis, and Coulter counter assays. Our data indicate that CellTiter-Blue, XTT, and CyQuant plate-based assays show increased values over control at low SiO2 NPs concentrations (0.001–0.01 g/L). SiO2 NPs show little-to-no interference with flow cytometry and Coulter counter assays, which not only were more reliable in determining cell viability and proliferation at low concentrations in vitro, but also identified changes in cell granularity and size that were not captured by the plate-based assays. At high SiO2 NP concentrations (1 g/L) all techniques indicated cytotoxicity. In concl...
ABSTRACT Most structural ceramics are manufactured using powders as starting materials. Since int... more ABSTRACT Most structural ceramics are manufactured using powders as starting materials. Since intelligent processing of powders and slurries is one of the vehicles to achieve improved manufacturing of ceramics, a consortium has been initiated at NIST to develop some of the necessary tools. The primary goal of this consortium is to develop improved surface chemical understanding of aqueous slurry processing with a focus on electroacoustics and nuclear magnetic resonance (NMR) techniques. Recent developments in electroacoustics have made it possible to carry out interface chemistry and agglomerate size distribution measurements in dense suspensions, thus making this technique uniquely suitable for online measurements. Underlying reasons for selecting these techniques and status of technical developments in their application are presented.
The adsorption of polyelectrolytes and nanoparticles onto patterned and curved surfaces is invest... more The adsorption of polyelectrolytes and nanoparticles onto patterned and curved surfaces is investigated (by fluorescence and electron microscopy) and exploited to produce anisotropic patchy particles. Various anisotropic properties are necessary for the self-assembly of complex structures. In this work, particles were bound temporarily to a substrate, so that part of their surfaces is occluded during subsequent surface modification by the
Intact liposome-based targeted nanoparticle delivery systems (NDS) are immobilized by non-selecti... more Intact liposome-based targeted nanoparticle delivery systems (NDS) are immobilized by non-selective binding and characterized by scanning probe microscopy (SPM) in a fluid imaging environment. The size, size distribution, functionality, and stability of an NDS with a payload consisting of a super-paramagnetic iron oxide contrast agent for magnetic resonance imaging are determined. SPM results are combined with information obtained by more familiar techniques such as superconducting quantum interference device (SQUID) magnetometry, dynamic light scattering, and electron microscopy. By integrating the methods presented in this work into the NDS formulation and manufacturing process, size-dependent statistical properties of the complex can be obtained and the structure-function relationship of individual, multi-component nanoscale entities can be assessed in a reliable and reproducible manner.
Synthetic surfactants are widely used in emulsion polymerization, but it is increasingly desirabl... more Synthetic surfactants are widely used in emulsion polymerization, but it is increasingly desirable to replace them with naturally derived molecules with a reduced environmental burden. This study demonstrates the use of saponins as biodegradable and renewable surfactants for emulsion polymerization. This chemical has been extracted from soapnuts by microwave assisted extraction and characterized in terms of surfactant properties prior to emulsion polymerization. The results in terms of particle size distribution and morphology control have been compared to those obtained with classical nonionic (NP40) or anionic (SDS) industrial surfactants. Microwave-extracted saponins were able to lead to latexes as stable as standard PS latex, as shown by the CMC and CCC measurements. The saponin-stabilized PS particles have been characterized in terms of particle size and distribution by Dynamic Light Scattering and Asymmetrical Flow Field Flow Fractionation. Monomodal and monodispersed particles ranging from 250 to 480 nm in terms of diameter with a particle size distribution below 1.03 have been synthesized.
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Papers by V. Hackley