Hydrogen fuel derived from clean solar energy (which is easily stored and free of greenhouse gas ... more Hydrogen fuel derived from clean solar energy (which is easily stored and free of greenhouse gas emissions) is an attempt to address predicted future global energy shortages. The purpose of this research is to investigate metal core/semiconductor shell nanoparticles to be illuminated with solar light to produce hydrogen fuel via water splitting (reducing and oxidizing). When a metal nanomaterial is illuminated with visible light, surface electrons exhibit high energy localized surface plasmon resonance (LSPR) which increases the local electric field more than 1000 times. Such hot electrons can tunnel to the shell surface to reduce water and produce H2. Wide-bandgap semiconductor shells absorb ultraviolet light, and the holes produced upon excitation serve to oxidize water .In this fashion, metal core/semiconductor shell nanoparticles, in combination with visible and ultravioletradiation, can be used to split water and produce hydrogen. Metal nanoparticles experience corrosion in wat...
Colloidal Nanocrystals for Biomedical Applications VIII, 2013
ABSTRACT Lanthanide fluoride colloidal nanocrystals offer a way to improve the diagnosis and trea... more ABSTRACT Lanthanide fluoride colloidal nanocrystals offer a way to improve the diagnosis and treatment of cancer through the enhanced absorption of ionizing radiation, in addition to providing visible luminescence. In order to explore this possibility, tests with a kilovoltage therapy unit manufactured by the Universal X-Ray Company were performed to estimate the energy sensitivity of this technique. La0.2Ce0.6Eu0.2F3 nanocrystals capped with polyethylene glycol of molecular weight 6000 were synthesized, suspended in deionized water, and made tolerant to biological ionic pressures by incubation with fetal bovine serum. These nanocrystals were characterized by dynamic light scattering, muffle furnace ashing, and photoluminescence spectroscopy. Clonogenic assays were performed on the cells to assay the cytotoxicity and radiotoxicity of the nanocrystals on the human pancreatic cancer cell line PANC-1, purchased from ATCC.
ABSTRACT Cystic fibrosis (CF) is an inherited childhood-onset life-shortening disease. It is char... more ABSTRACT Cystic fibrosis (CF) is an inherited childhood-onset life-shortening disease. It is characterized by increased respiratory production, leading to airway obstruction, chronic lung infection and inflammatory reactions. The most common bacteria causing persisting infections in people with CF is Pseudomonas aeruginosa. Superparamagnetic Fe3O4 iron oxide nanoparticles (NPs) conjugated to the antibiotic (tobramycin), guided by a gradient of the magnetic field or subjected to an oscillating magnetic field, show promise in improving the drug delivery across the mucus and P. aeruginosa biofilm to the bacteria. The question remains whether tobramycin needs to be released from the NPs after the penetration of the mucus barrier in order to act upon the pathogenic bacteria. We used a zero-length 1-ethyl-3-[3-dimethylaminopropyl] carbodiimide hydrochloride (EDC) crosslinking agent to couple tobramycin, via its amine groups, to the carboxyl groups on Fe3O4 NPs capped with citric acid. The therapeutic efficiency of Fe3O4 NPs attached to the drug versus that of the free drug was investigated in P. aeruginosa culture.
ABSTRACT We explore a novel concept of passive optically-enabled detection of thermal neutrons th... more ABSTRACT We explore a novel concept of passive optically-enabled detection of thermal neutrons that exploits transmutation of <sup align="right"> 164 Dy into <sup align="right"> 165 Ho. The concept relies on significant differences in optical properties of Dy and Ho and on our ability to find the most sensitive optical method of differentiating between Dy and Ho. While the concept applies equally well to bulk materials and to nanocrystals (NCs), the nanocrystalline approach is much more attractive due to its significantly lower cost, relative ease of colloidal synthesis of high quality NCs with controlled composition, and superior optical and mechanical properties of NCs compared to their bulk counterparts. One particular advantage of NCs for neutron detection is that in principle they can be integrated into a transparent host without causing optical scattering. Since Ho is known to have strong emission lines in mid-infrared, we considered potassium bromide (KBr), transparent in mid-IR spectral range, to be a suitable host for Dy-containing NCs. Here, we report on synthesis and characterisation of DyF<sub align="right"> 3 :10%Ce, HoF<sub align="right"> 3 :10%Ce, and DyF<sub align="right"> 3 :10%Ho,10%Ce NCs, their insertion into KBr matrix, and optical characterisation of the obtained nanocomposites, both non-irradiated and subjected to neutron irradiation.
Colloidal Nanocrystals for Biomedical Applications VIII, 2013
ABSTRACT Colloidal quantum dots (QDs) are of interest for a variety of biomedical applications, i... more ABSTRACT Colloidal quantum dots (QDs) are of interest for a variety of biomedical applications, including bioimaging, drug targeting, and photodynamic therapy. However, a significant limitation is that highly efficient photoluminescent QDs available commercially contain cadmium. Recent research has focused on cadmium-free QDs, which are anticipated to exhibit significantly lower cytotoxicity. Previous work has focused on InP and ZnO as alternative semiconductor materials for QDs. However, these nanoparticles have been shown to be cytotoxic. Recently, we have synthesized high quantum efficiency (exceeding 90%), color tunable MnSe/ZnSeS nanoparticles, as potentially attractive QDs for biomedical applications. Additionally, the manganese imparts magnetic properties on the QDs, which are important for magnetic field-guided transport, hyperthermia, and potentially magnetic resonance imaging (MRI). The QDs can be further biofunctionalized via conjugation to a ligand or a biomarker of disease, allowing combination of drug delivery with visual verification and colocalization due to the color tunability of the QDs.
ABSTRACT Iron oxide colloidal nanoparticles (ferrofluids) are investigated for application in the... more ABSTRACT Iron oxide colloidal nanoparticles (ferrofluids) are investigated for application in the treatment of cystic fibrosis lung infections, the leading cause of mortality in cystic fibrosis patients. We investigate the use of iron oxide nanoparticles to increase the effectiveness of administering antibiotics through aerosol inhalation using two mechanisms: directed particle movement in the presence of an inhomogeneous static external magnetic field and magnetic hyperthermia. Magnetic hyperthermia is an effective method for decreasing the viscosity of the mucus and biofilm, thereby enhancing drug, immune cell, and antibody penetration to the affected area. Iron oxide nanoparticles of various sizes and morphologies were synthesized and tested for specific losses (heating power). Nanoparticles in the superparamagnetic to ferromagnetic size range exhibited excellent heating power. Additionally, iron oxide / zinc selenide core/shell nanoparticles were prepared, in order to enable imaging of the iron oxide nanoparticles. We also report on synthesis and characterization of MnSe/ZnSeS alloyed quantum dots.
Colloidal Nanoparticles for Biomedical Applications IX, 2014
ABSTRACT Pseudomonas aeruginosa bacterium is a deadly pathogen, leading to respiratory failure in... more ABSTRACT Pseudomonas aeruginosa bacterium is a deadly pathogen, leading to respiratory failure in cystic fibrosis and nosocomial pneumonia, and responsible for high mortality rates in these diseases. P. aeruginosa has inherent as well as acquired resistance to many drug classes. In this paper, we investigate the effectiveness of two classes; aminoglycoside (tobramycin) and fluoroquinolone (ciprofloxacin) administered alone, as well as conjugated to iron oxide (magnetite) nanoparticles. P. aeruginosa possesses the ability to quickly alter its genetics to impart resistance to the presence of new, unrecognized treatments. As a response to this impending public health threat, we have synthesized and characterized magnetite nanoparticles capped with biodegradable short-chain carboxylic acid derivatives conjugated to common antibiotic drugs. The functionalized nanoparticles may carry the drug past the mucus and biofilm layers to target the bacterial colonies via magnetic gradient-guided transport. Additionally, the magnetic ferrofluid may be used under application of an oscillating magnetic field to raise the local temperature, causing biofilm disruption, slowed growth, and mechanical disruption. These abilities of the ferrofluid would also treat multi-drug resistant strains, which appear to be increasing in many nosocomial as well as acquired opportunistic infections. In this in vitro model, we show that the iron oxide alone can also inhibit bacterial growth and biofilm formation.
Amorphous mesoporous silica nanoparticles (&a... more Amorphous mesoporous silica nanoparticles ('protocells') that support surface lipid bilayers recently characterized in vitro as carrier constructs for small drug and DNA delivery are reported here as highly biocompatible both in vitro and in vivo, involving the brain and spinal cord following spinal delivery into the lumbosacral subarachnoid space (intrathecal; i.t.). Specifically, positively charged, 1, 2-Dioleoyl-3-Trimethylammonium-Propane (DOTAP)-cholesterol (DOTAP:Chol) liposome-formulated protocells revealed stable in vitro cargo release kinetics and cellular interleukin-10 (IL-10) transgene transfection. Recent approaches using synthetic non-viral vector platforms to deliver the pain-suppressive therapeutic transgene, IL-10, to the spinal subarachnoid space have yielded promising results in animal models of peripheral neuropathy, a condition involving aberrant neuronal communication within sensory pathways in the nervous system. Non-viral drug and gene delivery protocell platforms offer potential flexibility because cargo release-rates can be pH-dependent. We report here that i.t. delivery of protocells, with modified chemistry supporting a surface coating of DOTAP:Chol liposomes and containing the IL-10 transgene, results in functional suppression of pain-related behavior in rats for extended periods. This study is the first demonstration that protocell vectors offer amenable and enduring in vivo biological characteristics that can be applied to spinal gene delivery.
Iron oxide colloidal nanoparticles (ferrofluids) are investigated for application in the treatmen... more Iron oxide colloidal nanoparticles (ferrofluids) are investigated for application in the treatment of cystic fibrosis lung infections, the leading cause of mortality in cystic fibrosis patients. We investigate the use of iron oxide nanoparticles to increase the effectiveness of administering antibiotics through aerosol inhalation using two mechanisms: directed particle movement in the presence of an inhomogeneous static external magnetic field and magnetic hyperthermia. Magnetic hyperthermia is an effective method for decreasing the viscosity of ...
Naturally occurring dysprosium is attractive as a neutron detector because of its high thermal ne... more Naturally occurring dysprosium is attractive as a neutron detector because of its high thermal neutron capture cross section and high natural abundance. Neutron-induced transmutation of.
Hydrogen fuel derived from clean solar energy (which is easily stored and free of greenhouse gas ... more Hydrogen fuel derived from clean solar energy (which is easily stored and free of greenhouse gas emissions) is an attempt to address predicted future global energy shortages. The purpose of this research is to investigate metal core/semiconductor shell nanoparticles to be illuminated with solar light to produce hydrogen fuel via water splitting (reducing and oxidizing). When a metal nanomaterial is illuminated with visible light, surface electrons exhibit high energy localized surface plasmon resonance (LSPR) which increases the local electric field more than 1000 times. Such hot electrons can tunnel to the shell surface to reduce water and produce H2. Wide-bandgap semiconductor shells absorb ultraviolet light, and the holes produced upon excitation serve to oxidize water .In this fashion, metal core/semiconductor shell nanoparticles, in combination with visible and ultravioletradiation, can be used to split water and produce hydrogen. Metal nanoparticles experience corrosion in wat...
Colloidal Nanocrystals for Biomedical Applications VIII, 2013
ABSTRACT Lanthanide fluoride colloidal nanocrystals offer a way to improve the diagnosis and trea... more ABSTRACT Lanthanide fluoride colloidal nanocrystals offer a way to improve the diagnosis and treatment of cancer through the enhanced absorption of ionizing radiation, in addition to providing visible luminescence. In order to explore this possibility, tests with a kilovoltage therapy unit manufactured by the Universal X-Ray Company were performed to estimate the energy sensitivity of this technique. La0.2Ce0.6Eu0.2F3 nanocrystals capped with polyethylene glycol of molecular weight 6000 were synthesized, suspended in deionized water, and made tolerant to biological ionic pressures by incubation with fetal bovine serum. These nanocrystals were characterized by dynamic light scattering, muffle furnace ashing, and photoluminescence spectroscopy. Clonogenic assays were performed on the cells to assay the cytotoxicity and radiotoxicity of the nanocrystals on the human pancreatic cancer cell line PANC-1, purchased from ATCC.
ABSTRACT Cystic fibrosis (CF) is an inherited childhood-onset life-shortening disease. It is char... more ABSTRACT Cystic fibrosis (CF) is an inherited childhood-onset life-shortening disease. It is characterized by increased respiratory production, leading to airway obstruction, chronic lung infection and inflammatory reactions. The most common bacteria causing persisting infections in people with CF is Pseudomonas aeruginosa. Superparamagnetic Fe3O4 iron oxide nanoparticles (NPs) conjugated to the antibiotic (tobramycin), guided by a gradient of the magnetic field or subjected to an oscillating magnetic field, show promise in improving the drug delivery across the mucus and P. aeruginosa biofilm to the bacteria. The question remains whether tobramycin needs to be released from the NPs after the penetration of the mucus barrier in order to act upon the pathogenic bacteria. We used a zero-length 1-ethyl-3-[3-dimethylaminopropyl] carbodiimide hydrochloride (EDC) crosslinking agent to couple tobramycin, via its amine groups, to the carboxyl groups on Fe3O4 NPs capped with citric acid. The therapeutic efficiency of Fe3O4 NPs attached to the drug versus that of the free drug was investigated in P. aeruginosa culture.
ABSTRACT We explore a novel concept of passive optically-enabled detection of thermal neutrons th... more ABSTRACT We explore a novel concept of passive optically-enabled detection of thermal neutrons that exploits transmutation of <sup align="right"> 164 Dy into <sup align="right"> 165 Ho. The concept relies on significant differences in optical properties of Dy and Ho and on our ability to find the most sensitive optical method of differentiating between Dy and Ho. While the concept applies equally well to bulk materials and to nanocrystals (NCs), the nanocrystalline approach is much more attractive due to its significantly lower cost, relative ease of colloidal synthesis of high quality NCs with controlled composition, and superior optical and mechanical properties of NCs compared to their bulk counterparts. One particular advantage of NCs for neutron detection is that in principle they can be integrated into a transparent host without causing optical scattering. Since Ho is known to have strong emission lines in mid-infrared, we considered potassium bromide (KBr), transparent in mid-IR spectral range, to be a suitable host for Dy-containing NCs. Here, we report on synthesis and characterisation of DyF<sub align="right"> 3 :10%Ce, HoF<sub align="right"> 3 :10%Ce, and DyF<sub align="right"> 3 :10%Ho,10%Ce NCs, their insertion into KBr matrix, and optical characterisation of the obtained nanocomposites, both non-irradiated and subjected to neutron irradiation.
Colloidal Nanocrystals for Biomedical Applications VIII, 2013
ABSTRACT Colloidal quantum dots (QDs) are of interest for a variety of biomedical applications, i... more ABSTRACT Colloidal quantum dots (QDs) are of interest for a variety of biomedical applications, including bioimaging, drug targeting, and photodynamic therapy. However, a significant limitation is that highly efficient photoluminescent QDs available commercially contain cadmium. Recent research has focused on cadmium-free QDs, which are anticipated to exhibit significantly lower cytotoxicity. Previous work has focused on InP and ZnO as alternative semiconductor materials for QDs. However, these nanoparticles have been shown to be cytotoxic. Recently, we have synthesized high quantum efficiency (exceeding 90%), color tunable MnSe/ZnSeS nanoparticles, as potentially attractive QDs for biomedical applications. Additionally, the manganese imparts magnetic properties on the QDs, which are important for magnetic field-guided transport, hyperthermia, and potentially magnetic resonance imaging (MRI). The QDs can be further biofunctionalized via conjugation to a ligand or a biomarker of disease, allowing combination of drug delivery with visual verification and colocalization due to the color tunability of the QDs.
ABSTRACT Iron oxide colloidal nanoparticles (ferrofluids) are investigated for application in the... more ABSTRACT Iron oxide colloidal nanoparticles (ferrofluids) are investigated for application in the treatment of cystic fibrosis lung infections, the leading cause of mortality in cystic fibrosis patients. We investigate the use of iron oxide nanoparticles to increase the effectiveness of administering antibiotics through aerosol inhalation using two mechanisms: directed particle movement in the presence of an inhomogeneous static external magnetic field and magnetic hyperthermia. Magnetic hyperthermia is an effective method for decreasing the viscosity of the mucus and biofilm, thereby enhancing drug, immune cell, and antibody penetration to the affected area. Iron oxide nanoparticles of various sizes and morphologies were synthesized and tested for specific losses (heating power). Nanoparticles in the superparamagnetic to ferromagnetic size range exhibited excellent heating power. Additionally, iron oxide / zinc selenide core/shell nanoparticles were prepared, in order to enable imaging of the iron oxide nanoparticles. We also report on synthesis and characterization of MnSe/ZnSeS alloyed quantum dots.
Colloidal Nanoparticles for Biomedical Applications IX, 2014
ABSTRACT Pseudomonas aeruginosa bacterium is a deadly pathogen, leading to respiratory failure in... more ABSTRACT Pseudomonas aeruginosa bacterium is a deadly pathogen, leading to respiratory failure in cystic fibrosis and nosocomial pneumonia, and responsible for high mortality rates in these diseases. P. aeruginosa has inherent as well as acquired resistance to many drug classes. In this paper, we investigate the effectiveness of two classes; aminoglycoside (tobramycin) and fluoroquinolone (ciprofloxacin) administered alone, as well as conjugated to iron oxide (magnetite) nanoparticles. P. aeruginosa possesses the ability to quickly alter its genetics to impart resistance to the presence of new, unrecognized treatments. As a response to this impending public health threat, we have synthesized and characterized magnetite nanoparticles capped with biodegradable short-chain carboxylic acid derivatives conjugated to common antibiotic drugs. The functionalized nanoparticles may carry the drug past the mucus and biofilm layers to target the bacterial colonies via magnetic gradient-guided transport. Additionally, the magnetic ferrofluid may be used under application of an oscillating magnetic field to raise the local temperature, causing biofilm disruption, slowed growth, and mechanical disruption. These abilities of the ferrofluid would also treat multi-drug resistant strains, which appear to be increasing in many nosocomial as well as acquired opportunistic infections. In this in vitro model, we show that the iron oxide alone can also inhibit bacterial growth and biofilm formation.
Amorphous mesoporous silica nanoparticles (&a... more Amorphous mesoporous silica nanoparticles ('protocells') that support surface lipid bilayers recently characterized in vitro as carrier constructs for small drug and DNA delivery are reported here as highly biocompatible both in vitro and in vivo, involving the brain and spinal cord following spinal delivery into the lumbosacral subarachnoid space (intrathecal; i.t.). Specifically, positively charged, 1, 2-Dioleoyl-3-Trimethylammonium-Propane (DOTAP)-cholesterol (DOTAP:Chol) liposome-formulated protocells revealed stable in vitro cargo release kinetics and cellular interleukin-10 (IL-10) transgene transfection. Recent approaches using synthetic non-viral vector platforms to deliver the pain-suppressive therapeutic transgene, IL-10, to the spinal subarachnoid space have yielded promising results in animal models of peripheral neuropathy, a condition involving aberrant neuronal communication within sensory pathways in the nervous system. Non-viral drug and gene delivery protocell platforms offer potential flexibility because cargo release-rates can be pH-dependent. We report here that i.t. delivery of protocells, with modified chemistry supporting a surface coating of DOTAP:Chol liposomes and containing the IL-10 transgene, results in functional suppression of pain-related behavior in rats for extended periods. This study is the first demonstration that protocell vectors offer amenable and enduring in vivo biological characteristics that can be applied to spinal gene delivery.
Iron oxide colloidal nanoparticles (ferrofluids) are investigated for application in the treatmen... more Iron oxide colloidal nanoparticles (ferrofluids) are investigated for application in the treatment of cystic fibrosis lung infections, the leading cause of mortality in cystic fibrosis patients. We investigate the use of iron oxide nanoparticles to increase the effectiveness of administering antibiotics through aerosol inhalation using two mechanisms: directed particle movement in the presence of an inhomogeneous static external magnetic field and magnetic hyperthermia. Magnetic hyperthermia is an effective method for decreasing the viscosity of ...
Naturally occurring dysprosium is attractive as a neutron detector because of its high thermal ne... more Naturally occurring dysprosium is attractive as a neutron detector because of its high thermal neutron capture cross section and high natural abundance. Neutron-induced transmutation of.
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Papers by Leisha Armijo