Vicki Colvin | Rice University (original) (raw)
Papers by Vicki Colvin
Water Research, 2011
Photocatalysis Silver Titanium dioxide Virus a b s t r a c t Photocatalytic inactivation of virus... more Photocatalysis Silver Titanium dioxide Virus a b s t r a c t Photocatalytic inactivation of viruses and other microorganisms is a promising technology that has been increasingly utilized in recent years. In this study, photocatalytic silver doped titanium dioxide nanoparticles (nAg/TiO 2 ) were investigated for their capability of inactivating Bacteriophage MS2 in aqueous media. Nano-sized Ag deposits were formed on two commercial TiO 2 nanopowders using a photochemical reduction method. The MS2 inactivation kinetics of nAg/TiO 2 was compared to the base TiO 2 material and silver ions leached from the catalyst. The inactivation rate of MS2 was enhanced by more than 5 fold depending on the base TiO 2 material, and the inactivation efficiency increased with increasing silver content. The increased production of hydroxyl free radicals was found to be responsible for the enhanced viral inactivation.
Nano Letters, 2005
Analytical ultracentrifugation (AU) provides a general way to probe the polydispersity of nanopar... more Analytical ultracentrifugation (AU) provides a general way to probe the polydispersity of nanoparticles and the formation of bioconjugates in solution. Unconjugated gold nanocrystals show sedimentation coefficient distributions that are in agreement with size distributions as measured by TEM. AU is sensitive to the size/shape changes elicited by conjugation, in this case to lactose repressor (LacI). AU data reveal saturating protein concentrations for conjugates that correspond to the measured stoichiometry of the complex under these conditions.
IEEE Transactions on Nanotechnology, 2006
Certain virus structures can be assembled in the form of a periodic lattice with nanometer-range ... more Certain virus structures can be assembled in the form of a periodic lattice with nanometer-range ordering. Cowpea mosaic virus is crystallized in body-centered-cubic geometry and used as a template for fabrication of metallized thin films with three-dimensional morphology. Calculations predict that these crystals exhibit a normal-incidence reflectivity of 7% for wavelengths around 35 nm, which can be utilized for soft
A quantitative model is presented to describe the formation of volume holograms in a polymeric me... more A quantitative model is presented to describe the formation of volume holograms in a polymeric medium containing photopolymerizable acrylate monomers that undergo spatially modulated gelation as a result of exposure to a visible “write” beam. The model refines the simple diffusion model of Zhao and Mouroulis [J. Mod. Opt. 41, 1929 (1994)], by including cure dependence of both the photoreaction
Physical Review Letters, 1999
We report observations of the optical stop band of periodic planar arrays of submicron silica sph... more We report observations of the optical stop band of periodic planar arrays of submicron silica spheres, and of macroporous polymers grown from these silica templates. The stop-band width and peak attenuation depend on the number of layers and on the dielectric contrast between the spheres and the interstitial regions, both of which are experimentally controlled. The results are compared to
In the wake of growing pressures to make scholarly knowledge commercially relevant via translatio... more In the wake of growing pressures to make scholarly knowledge commercially relevant via translation into intellectual property, various techno-scientific communities have mobilized to create open access/open source experiments. These efforts are based on the ideas and success of free and open source software, and generally try to exploit two salient features: increased openness and circulation, and distributed collective innovation. Transferring
We demonstrate a novel quantum dot based probe with inherent signal amplification upon interactio... more We demonstrate a novel quantum dot based probe with inherent signal amplification upon interaction with a targeted proteolytic enzyme. This probe may be useful for imaging in cancer detection and diagnosis. In this system, quantum dots (QDs) are bound to gold nanoparticles (AuNPs) via a proteolytically-degradable peptide sequence to non-radiatively suppress luminescence. A 71% reduction in luminescence was achieved with
Magnetic separations at very low magnetic field gradients (<100 tesla per meter) can now be appli... more Magnetic separations at very low magnetic field gradients (<100 tesla per meter) can now be applied to diverse problems, such as point-of-use water purification and the simultaneous separation of complex mixtures. High-surface area and monodisperse magnetite (Fe 3 O 4 ) nanocrystals (NCs) were shown to respond to low fields in a size-dependent fashion. The particles apparently do not act independently in the separation but rather reversibly aggregate through the resulting high-field gradients present at their surfaces. Using the high specific surface area of Fe 3 O 4 NCs that were 12 nanometers in diameter, we reduced the mass of waste associated with arsenic removal from water by orders of magnitude. Additionally, the size dependence of magnetic separation permitted mixtures of 4-and 12-nanometer-sized Fe 3 O 4 NCs to be separated by the application of different magnetic fields.
Biochemical and Biophysical Research Communications - BIOCHEM BIOPHYS RES COMMUN, 2006
Semiconductor nanocrystals are 1–10nm inorganic particles with unique size-dependent optical and ... more Semiconductor nanocrystals are 1–10nm inorganic particles with unique size-dependent optical and electrical properties due to quantum confinement (so they are also called quantum dots). Quantum dots are new types of fluorescent materials for biological labeling with high quantum efficiency, long-term photostability, narrow emission, and continuous absorption spectra. Here, we discuss the recent development in making water-soluble quantum dots and related cytotoxicity for biomedical applications.
Nature Materials - NAT MATER, 2003
orm ever follows function,"asserted architect Louis Henri Sullivan,providing a maxim for designer... more orm ever follows function,"asserted architect Louis Henri Sullivan,providing a maxim for designers of all persuasions. His protégé,Frank Lloyd Wright,preferred "Form and function should be one."Such adages express the widely held conviction that shape and utility or properties are inextricably linked.The experimental work by Kan et al. described on page 155 of this issue 1 provides a compelling demonstration of this principle. Kan and colleagues show that the electronic structure and optical properties (that is,the quantum confinement effects) of rod-like semiconductor nanocrystals depend sensitively on the ratio of their length and diameter.Thus,bodybuilders,distance runners, architects and quantum mechanics agree: In function, performance and behaviour,shape matters.
Toxicology and Applied Pharmacology, 2008
Quantum dots nanoparticles have novel optical properties for biomedical applications and electron... more Quantum dots nanoparticles have novel optical properties for biomedical applications and electronics, but little is known about their skin permeability and interaction with cells. QD621 are nail-shaped nanoparticles that contain a cadmium/selenide core with a cadmium sulfide shell coated with polyethylene glycol (PEG) and are soluble in water. QD were topically applied to porcine skin flow-through diffusion cells to assess penetration at 1 μM, 2 μM and 10 μM for 24 h. QD were also studied in human epidermal keratinocytes (HEK) to determine cellular uptake, cytotoxicity and inflammatory potential. Confocal microscopy depicted the penetration of QD621 through the uppermost stratum corneum (SC) layers of the epidermis and fluorescence was found primarily in the SC and near hair follicles. QD were found in the intercellular lipid bilayers of the SC by transmission electron microscopy (TEM). Inductively coupled plasma-optical emission spectroscopy (ICP-OES) analysis for cadmium (Cd) and fluorescence for QD both did not detect Cd nor fluorescence signal in the perfusate at any time point or concentration. In HEK, viability decreased significantly (p b 0.05) from 1.25 nM to 10nM after 24 h and 48 h. There was a significant increase in IL-6 at 1.25 nM to 10 nM, while IL-8 increased from 2.5nM to 10nM after 24 h and 48 h. TEM of HEK treated with 10 nM of QD621 at 24 h depicted QD in cytoplasmic vacuoles and at the periphery of the cell membranes. These results indicate that porcine skin penetration of QD621 is minimal and limited primarily to the outer SC layers, yet if the skin were damaged allowing direct QD exposure to skin or keratinocytes, an inflammatory response could be initiated.
Toxicological Sciences, 2006
Pulmonary toxicology studies in rats demonstrate that nanoparticles administered to the lung are ... more Pulmonary toxicology studies in rats demonstrate that nanoparticles administered to the lung are more toxic than larger, fine-sized particles of similar chemistry at identical mass concentrations. The aim of this study was to evaluate the acute lung toxicity in rats of intratracheally instilled pigment-grade TiO2 particles (rutile-type particle size = approximately 300 nm) versus nanoscale TiO2 rods (anatase = 200 nm x 35 nm) or nanoscale TiO2 dots (anatase = approximately 10 nm) compared with a positive control particle type, quartz. Groups of rats were instilled with doses of 1 or 5 mg/kg of the various particle types in phosphate-buffered saline (PBS). Subsequently, the lungs of PBS- and particle-exposed rats were assessed using bronchoalveolar lavage fluid biomarkers, cell proliferation methods, and by the histopathological evaluation of lung tissue at 24 h, 1 week, 1 month, and 3 months postinstillation exposure. Exposures to nanoscale TiO2 rods or nanoscale TiO2 dots produced transient inflammatory and cell injury effects at 24 h postexposure (pe) and were not different from the pulmonary effects of larger sized TiO2 particle exposures. In contrast, pulmonary exposures to quartz particles in rats produced a dose-dependent lung inflammatory response characterized by neutrophils and foamy lipid-containing alveolar macrophage accumulation as well as evidence of early lung tissue thickening consistent with the development of pulmonary fibrosis. The results described herein provide the first example of nanoscale particle types which are not more cytotoxic or inflammogenic to the lung compared to larger sized particles of similar composition. Furthermore, these findings run counter to the postulation that surface area is a major factor associated with the pulmonary toxicity of nanoscale particle types.
Toxicological Sciences, 2006
Pulmonary toxicology studies in rats demonstrate that nanoparticles are more toxic than fine-size... more Pulmonary toxicology studies in rats demonstrate that nanoparticles are more toxic than fine-sized particles of similar chemistry. This study, however, provides evidence to contradict this theory. The aims of the study were (1) to compare the toxicity of synthetic 50 nm nanoquartz I particles versus (mined) Min-U-Sil quartz (~500 nm); the toxicity of synthetic 12 nm nanoquartz II particles versus (mined) Min-U-Sil (~500 nm) versus (synthetic) fine-quartz particles (300 nm); and (2) to evaluate the surface activities among the samples as they relate to toxicity. Wellcharacterized samples were tested for surface activity and hemolytic potential. In addition, groups of rats were instilled with either doses of 1 or 5 mg/kg of carbonyl iron (CI) or various aquartz particle types in phosphate-buffered saline solution and subsequently assessed using bronchoalveolar lavage fluid biomarkers, cell proliferation, and histopathological evaluation of lung tissue at 24 h, 1 week, 1 month, and 3 months postexposure. Exposures to the various a-quartz particles produced differential degrees of pulmonary inflammation and cytotoxicity, which were not always consistent with particle size but correlated with surface activity, particularly hemolytic potential. Lung tissue evaluations of three of the quartz samples demonstrated ''typical'' quartzrelated effects-dose-dependent lung inflammatory macrophage accumulation responses concomitant with early development of pulmonary fibrosis. The various a-quartz-related effects were similar qualitatively but with different potencies. The range of particle-related toxicities and histopathological effects in descending order were nanoscale quartz II ¼ Min-U-Sil quartz > fine quartz > nanoscale quartz I > CI particles. The results demonstrate that the pulmonary toxicities of a-quartz particles appear to correlate better with surface activity than particle size and surface area.
Small, 2010
The development and optimization of near-infrared (NIR)-absorbing nanoparticles for use as photot... more The development and optimization of near-infrared (NIR)-absorbing nanoparticles for use as photothermal cancer therapeutic agents has been ongoing. This work exploits the properties of gold/gold sulfide NIR-absorbing nanoparticles (approximately 35-55 nm) that provide higher absorption (98% absorption and 2% scattering for gold/gold sulfide versus 70% absorption and 30% scattering for gold/silica nanoshells) as well as potentially better tumor penetration. The ability to ablate tumor cells in vitro and efficacy for photothermal cancer therapy is demonstrated, and an in vivo model shows significantly increased long-term, tumor-free survival. Furthermore, enhanced circulation and biodistribution is observed in vivo. This class of NIR-absorbing nanoparticles has the potential to improve upon photothermal tumor ablation for cancer therapy.
Science and Technology of Advanced Materials, 2007
Higher environmental standards have made the removal of arsenic from water an important problem f... more Higher environmental standards have made the removal of arsenic from water an important problem for environmental engineering. Iron oxide is a particularly interesting sorbent to consider for this application. Its magnetic properties allow relatively routine dispersal and recovery of the adsorbent into and from groundwater or industrial processing facilities; in addition, iron oxide has strong and specific interactions with both As(III) and As(V). Finally, this material can be produced with nanoscale dimensions, which enhance both its capacity and removal. The objective of this study is to evaluate the potential arsenic adsorption by nanoscale iron oxides, specifically magnetite (Fe 3 O 4 ) nanoparticles. We focus on the effect of Fe 3 O 4 particle size on the adsorption and desorption behavior of As(III) and As(V). The results show that the nanoparticle size has a dramatic effect on the adsorption and desorption of arsenic. As particle size is decreased from 300 to 12 nm the adsorption capacities for both As(III) and As(V) increase nearly 200 times. Interestingly, such an increase is more than expected from simple considerations of surface area and suggests that nanoscale iron oxide materials sorb arsenic through different means than bulk systems. The desorption process, however, exhibits some hysteresis with the effect becoming more pronounced with small nanoparticles. This hysteresis most likely results from a higher arsenic affinity for Fe 3 O 4 nanoparticles. This work suggests that Fe 3 O 4 nanocrystals and magnetic separations offer a promising method for arsenic removal. r
Science, 2001
We report a nanoscale "lost-wax" method for forming colloids with size distribu... more We report a nanoscale "lost-wax" method for forming colloids with size distributions around 5% and their corresponding colloidal crystals. Macroporous polymer templates are first prepared from a silica colloidal crystal. We then use the uniform and interconnected voids of the porous polymer to generate a wide variety of highly monodisperse inorganic, polymeric, and metallic solid and core-shell colloids, as well as hollow colloids with controllable shell thickness, as colloidal crystals. We can also uniformly deform the polymer template to alter colloidal shape and demonstrate the formation of elliptical particles with precisely controlled aspect ratios.
Water Research, 2011
Photocatalysis Silver Titanium dioxide Virus a b s t r a c t Photocatalytic inactivation of virus... more Photocatalysis Silver Titanium dioxide Virus a b s t r a c t Photocatalytic inactivation of viruses and other microorganisms is a promising technology that has been increasingly utilized in recent years. In this study, photocatalytic silver doped titanium dioxide nanoparticles (nAg/TiO 2 ) were investigated for their capability of inactivating Bacteriophage MS2 in aqueous media. Nano-sized Ag deposits were formed on two commercial TiO 2 nanopowders using a photochemical reduction method. The MS2 inactivation kinetics of nAg/TiO 2 was compared to the base TiO 2 material and silver ions leached from the catalyst. The inactivation rate of MS2 was enhanced by more than 5 fold depending on the base TiO 2 material, and the inactivation efficiency increased with increasing silver content. The increased production of hydroxyl free radicals was found to be responsible for the enhanced viral inactivation.
Nano Letters, 2005
Analytical ultracentrifugation (AU) provides a general way to probe the polydispersity of nanopar... more Analytical ultracentrifugation (AU) provides a general way to probe the polydispersity of nanoparticles and the formation of bioconjugates in solution. Unconjugated gold nanocrystals show sedimentation coefficient distributions that are in agreement with size distributions as measured by TEM. AU is sensitive to the size/shape changes elicited by conjugation, in this case to lactose repressor (LacI). AU data reveal saturating protein concentrations for conjugates that correspond to the measured stoichiometry of the complex under these conditions.
IEEE Transactions on Nanotechnology, 2006
Certain virus structures can be assembled in the form of a periodic lattice with nanometer-range ... more Certain virus structures can be assembled in the form of a periodic lattice with nanometer-range ordering. Cowpea mosaic virus is crystallized in body-centered-cubic geometry and used as a template for fabrication of metallized thin films with three-dimensional morphology. Calculations predict that these crystals exhibit a normal-incidence reflectivity of 7% for wavelengths around 35 nm, which can be utilized for soft
A quantitative model is presented to describe the formation of volume holograms in a polymeric me... more A quantitative model is presented to describe the formation of volume holograms in a polymeric medium containing photopolymerizable acrylate monomers that undergo spatially modulated gelation as a result of exposure to a visible “write” beam. The model refines the simple diffusion model of Zhao and Mouroulis [J. Mod. Opt. 41, 1929 (1994)], by including cure dependence of both the photoreaction
Physical Review Letters, 1999
We report observations of the optical stop band of periodic planar arrays of submicron silica sph... more We report observations of the optical stop band of periodic planar arrays of submicron silica spheres, and of macroporous polymers grown from these silica templates. The stop-band width and peak attenuation depend on the number of layers and on the dielectric contrast between the spheres and the interstitial regions, both of which are experimentally controlled. The results are compared to
In the wake of growing pressures to make scholarly knowledge commercially relevant via translatio... more In the wake of growing pressures to make scholarly knowledge commercially relevant via translation into intellectual property, various techno-scientific communities have mobilized to create open access/open source experiments. These efforts are based on the ideas and success of free and open source software, and generally try to exploit two salient features: increased openness and circulation, and distributed collective innovation. Transferring
We demonstrate a novel quantum dot based probe with inherent signal amplification upon interactio... more We demonstrate a novel quantum dot based probe with inherent signal amplification upon interaction with a targeted proteolytic enzyme. This probe may be useful for imaging in cancer detection and diagnosis. In this system, quantum dots (QDs) are bound to gold nanoparticles (AuNPs) via a proteolytically-degradable peptide sequence to non-radiatively suppress luminescence. A 71% reduction in luminescence was achieved with
Magnetic separations at very low magnetic field gradients (<100 tesla per meter) can now be appli... more Magnetic separations at very low magnetic field gradients (<100 tesla per meter) can now be applied to diverse problems, such as point-of-use water purification and the simultaneous separation of complex mixtures. High-surface area and monodisperse magnetite (Fe 3 O 4 ) nanocrystals (NCs) were shown to respond to low fields in a size-dependent fashion. The particles apparently do not act independently in the separation but rather reversibly aggregate through the resulting high-field gradients present at their surfaces. Using the high specific surface area of Fe 3 O 4 NCs that were 12 nanometers in diameter, we reduced the mass of waste associated with arsenic removal from water by orders of magnitude. Additionally, the size dependence of magnetic separation permitted mixtures of 4-and 12-nanometer-sized Fe 3 O 4 NCs to be separated by the application of different magnetic fields.
Biochemical and Biophysical Research Communications - BIOCHEM BIOPHYS RES COMMUN, 2006
Semiconductor nanocrystals are 1–10nm inorganic particles with unique size-dependent optical and ... more Semiconductor nanocrystals are 1–10nm inorganic particles with unique size-dependent optical and electrical properties due to quantum confinement (so they are also called quantum dots). Quantum dots are new types of fluorescent materials for biological labeling with high quantum efficiency, long-term photostability, narrow emission, and continuous absorption spectra. Here, we discuss the recent development in making water-soluble quantum dots and related cytotoxicity for biomedical applications.
Nature Materials - NAT MATER, 2003
orm ever follows function,"asserted architect Louis Henri Sullivan,providing a maxim for designer... more orm ever follows function,"asserted architect Louis Henri Sullivan,providing a maxim for designers of all persuasions. His protégé,Frank Lloyd Wright,preferred "Form and function should be one."Such adages express the widely held conviction that shape and utility or properties are inextricably linked.The experimental work by Kan et al. described on page 155 of this issue 1 provides a compelling demonstration of this principle. Kan and colleagues show that the electronic structure and optical properties (that is,the quantum confinement effects) of rod-like semiconductor nanocrystals depend sensitively on the ratio of their length and diameter.Thus,bodybuilders,distance runners, architects and quantum mechanics agree: In function, performance and behaviour,shape matters.
Toxicology and Applied Pharmacology, 2008
Quantum dots nanoparticles have novel optical properties for biomedical applications and electron... more Quantum dots nanoparticles have novel optical properties for biomedical applications and electronics, but little is known about their skin permeability and interaction with cells. QD621 are nail-shaped nanoparticles that contain a cadmium/selenide core with a cadmium sulfide shell coated with polyethylene glycol (PEG) and are soluble in water. QD were topically applied to porcine skin flow-through diffusion cells to assess penetration at 1 μM, 2 μM and 10 μM for 24 h. QD were also studied in human epidermal keratinocytes (HEK) to determine cellular uptake, cytotoxicity and inflammatory potential. Confocal microscopy depicted the penetration of QD621 through the uppermost stratum corneum (SC) layers of the epidermis and fluorescence was found primarily in the SC and near hair follicles. QD were found in the intercellular lipid bilayers of the SC by transmission electron microscopy (TEM). Inductively coupled plasma-optical emission spectroscopy (ICP-OES) analysis for cadmium (Cd) and fluorescence for QD both did not detect Cd nor fluorescence signal in the perfusate at any time point or concentration. In HEK, viability decreased significantly (p b 0.05) from 1.25 nM to 10nM after 24 h and 48 h. There was a significant increase in IL-6 at 1.25 nM to 10 nM, while IL-8 increased from 2.5nM to 10nM after 24 h and 48 h. TEM of HEK treated with 10 nM of QD621 at 24 h depicted QD in cytoplasmic vacuoles and at the periphery of the cell membranes. These results indicate that porcine skin penetration of QD621 is minimal and limited primarily to the outer SC layers, yet if the skin were damaged allowing direct QD exposure to skin or keratinocytes, an inflammatory response could be initiated.
Toxicological Sciences, 2006
Pulmonary toxicology studies in rats demonstrate that nanoparticles administered to the lung are ... more Pulmonary toxicology studies in rats demonstrate that nanoparticles administered to the lung are more toxic than larger, fine-sized particles of similar chemistry at identical mass concentrations. The aim of this study was to evaluate the acute lung toxicity in rats of intratracheally instilled pigment-grade TiO2 particles (rutile-type particle size = approximately 300 nm) versus nanoscale TiO2 rods (anatase = 200 nm x 35 nm) or nanoscale TiO2 dots (anatase = approximately 10 nm) compared with a positive control particle type, quartz. Groups of rats were instilled with doses of 1 or 5 mg/kg of the various particle types in phosphate-buffered saline (PBS). Subsequently, the lungs of PBS- and particle-exposed rats were assessed using bronchoalveolar lavage fluid biomarkers, cell proliferation methods, and by the histopathological evaluation of lung tissue at 24 h, 1 week, 1 month, and 3 months postinstillation exposure. Exposures to nanoscale TiO2 rods or nanoscale TiO2 dots produced transient inflammatory and cell injury effects at 24 h postexposure (pe) and were not different from the pulmonary effects of larger sized TiO2 particle exposures. In contrast, pulmonary exposures to quartz particles in rats produced a dose-dependent lung inflammatory response characterized by neutrophils and foamy lipid-containing alveolar macrophage accumulation as well as evidence of early lung tissue thickening consistent with the development of pulmonary fibrosis. The results described herein provide the first example of nanoscale particle types which are not more cytotoxic or inflammogenic to the lung compared to larger sized particles of similar composition. Furthermore, these findings run counter to the postulation that surface area is a major factor associated with the pulmonary toxicity of nanoscale particle types.
Toxicological Sciences, 2006
Pulmonary toxicology studies in rats demonstrate that nanoparticles are more toxic than fine-size... more Pulmonary toxicology studies in rats demonstrate that nanoparticles are more toxic than fine-sized particles of similar chemistry. This study, however, provides evidence to contradict this theory. The aims of the study were (1) to compare the toxicity of synthetic 50 nm nanoquartz I particles versus (mined) Min-U-Sil quartz (~500 nm); the toxicity of synthetic 12 nm nanoquartz II particles versus (mined) Min-U-Sil (~500 nm) versus (synthetic) fine-quartz particles (300 nm); and (2) to evaluate the surface activities among the samples as they relate to toxicity. Wellcharacterized samples were tested for surface activity and hemolytic potential. In addition, groups of rats were instilled with either doses of 1 or 5 mg/kg of carbonyl iron (CI) or various aquartz particle types in phosphate-buffered saline solution and subsequently assessed using bronchoalveolar lavage fluid biomarkers, cell proliferation, and histopathological evaluation of lung tissue at 24 h, 1 week, 1 month, and 3 months postexposure. Exposures to the various a-quartz particles produced differential degrees of pulmonary inflammation and cytotoxicity, which were not always consistent with particle size but correlated with surface activity, particularly hemolytic potential. Lung tissue evaluations of three of the quartz samples demonstrated ''typical'' quartzrelated effects-dose-dependent lung inflammatory macrophage accumulation responses concomitant with early development of pulmonary fibrosis. The various a-quartz-related effects were similar qualitatively but with different potencies. The range of particle-related toxicities and histopathological effects in descending order were nanoscale quartz II ¼ Min-U-Sil quartz > fine quartz > nanoscale quartz I > CI particles. The results demonstrate that the pulmonary toxicities of a-quartz particles appear to correlate better with surface activity than particle size and surface area.
Small, 2010
The development and optimization of near-infrared (NIR)-absorbing nanoparticles for use as photot... more The development and optimization of near-infrared (NIR)-absorbing nanoparticles for use as photothermal cancer therapeutic agents has been ongoing. This work exploits the properties of gold/gold sulfide NIR-absorbing nanoparticles (approximately 35-55 nm) that provide higher absorption (98% absorption and 2% scattering for gold/gold sulfide versus 70% absorption and 30% scattering for gold/silica nanoshells) as well as potentially better tumor penetration. The ability to ablate tumor cells in vitro and efficacy for photothermal cancer therapy is demonstrated, and an in vivo model shows significantly increased long-term, tumor-free survival. Furthermore, enhanced circulation and biodistribution is observed in vivo. This class of NIR-absorbing nanoparticles has the potential to improve upon photothermal tumor ablation for cancer therapy.
Science and Technology of Advanced Materials, 2007
Higher environmental standards have made the removal of arsenic from water an important problem f... more Higher environmental standards have made the removal of arsenic from water an important problem for environmental engineering. Iron oxide is a particularly interesting sorbent to consider for this application. Its magnetic properties allow relatively routine dispersal and recovery of the adsorbent into and from groundwater or industrial processing facilities; in addition, iron oxide has strong and specific interactions with both As(III) and As(V). Finally, this material can be produced with nanoscale dimensions, which enhance both its capacity and removal. The objective of this study is to evaluate the potential arsenic adsorption by nanoscale iron oxides, specifically magnetite (Fe 3 O 4 ) nanoparticles. We focus on the effect of Fe 3 O 4 particle size on the adsorption and desorption behavior of As(III) and As(V). The results show that the nanoparticle size has a dramatic effect on the adsorption and desorption of arsenic. As particle size is decreased from 300 to 12 nm the adsorption capacities for both As(III) and As(V) increase nearly 200 times. Interestingly, such an increase is more than expected from simple considerations of surface area and suggests that nanoscale iron oxide materials sorb arsenic through different means than bulk systems. The desorption process, however, exhibits some hysteresis with the effect becoming more pronounced with small nanoparticles. This hysteresis most likely results from a higher arsenic affinity for Fe 3 O 4 nanoparticles. This work suggests that Fe 3 O 4 nanocrystals and magnetic separations offer a promising method for arsenic removal. r
Science, 2001
We report a nanoscale "lost-wax" method for forming colloids with size distribu... more We report a nanoscale "lost-wax" method for forming colloids with size distributions around 5% and their corresponding colloidal crystals. Macroporous polymer templates are first prepared from a silica colloidal crystal. We then use the uniform and interconnected voids of the porous polymer to generate a wide variety of highly monodisperse inorganic, polymeric, and metallic solid and core-shell colloids, as well as hollow colloids with controllable shell thickness, as colloidal crystals. We can also uniformly deform the polymer template to alter colloidal shape and demonstrate the formation of elliptical particles with precisely controlled aspect ratios.