Matching Items (6)

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Amino Acid Templated Gold Nanoparticles as Sensors of Ionizing Radiation

Description

This research addresses the need for improvement in radiation sensors for applications of ionizing radiation such as radiotherapy. The current sensors involved are polymer gel dosimeters, MOSFETs, radio-chromic films, etc.

This research addresses the need for improvement in radiation sensors for applications of ionizing radiation such as radiotherapy. The current sensors involved are polymer gel dosimeters, MOSFETs, radio-chromic films, etc. Most of the sensors involved require expensive equipment's and processing facilities for readout. There is still a need to develop better sensors that can be clinically applied. There are numerous groups around the world trying to conceive a better dosimeter. One of the radiation sensors that was developed recently was based on fluorescence signal emitted from the sensor. To advance the field of radiation sensors, a visual indicator has been developed in-lab as a method of detect ionizing radiation. The intensity of change in color is directly dependent on the amount of incident ionizing radiation. An aqueous gold nanoparticle sensor can be used to accurately determine the incident amount of ionizing radiation1. A gold nanoparticle sensor has been developed in lab with the use of hexadecyltrimethylammonium bromide (C16TAB) as the templating molecule. In the presence of ionizing radiation, the colorless gold salt is reduced and templated, creating a dispersion within the fluid1. The formation of suspended nanoparticles leads to a color change that can be visually detected and accurately analyzed through the employment of a spectrometer. Unfortunately, the toxicity of C16TAB is high. It is expected the toxicity can be reduced by replacing C16TAB with an amino acid, as amino acids can act as templating molecules in the solution and many are naturally occuring2. The experiments included a screening of 20 natural amino acids and 12 unnatural amino acids with the gold salt solution in the presence of ionizing radiation. Stability and absorbance testing was conducted on the amino acid sensors. Additional screening of lead amino acid sensors at various concentrations of irradiation was conducted.

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Date Created
  • 2017-05

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Photoreactive and Electrochemical Properties of Vesicle Encapsulated Nanoparticles: Implications for Application in Retinal Stimulation

Description

Electrical stimulation has previously been effective in neural cells activation within retinas affected by degenerative retinal disease. However current technology has at most allowed blind individuals to perceive light without

Electrical stimulation has previously been effective in neural cells activation within retinas affected by degenerative retinal disease. However current technology has at most allowed blind individuals to perceive light without significant resolution, as implants are limited by the spatial constraints of the eye. Photoreactive nanoparticles may provide a solution to this issue, as their small size would allow for the incorporation of higher numbers of stimulatory elements, thus increasing visual resolution. Semiconductive nanocrystal quantum dots (QDs) and gold nanoparticles (AuNPs) both exhibit photoreactive properties which may result in sufficient electrical stimulation to activate neural cells in the retina. This study investigated the electrochemistry and photoreactivity of QDs and AuNPs encapsulated within the hydrophobic region of small unilamellar lipid vesicles (SUVs) to evaluate their potential for application in retinal stimulation. Absorbance of the constructs was evaluated on the day of fabrication and 24 hours later to determine the ability of the particles to react to light while encapsulated, as well as to evaluate stability of the construct over time. Electrical impedance spectroscopy (EIS) was conducted at both time points to determine the electrochemical character of the bilayer and further evaluate construct stability. Although quantum dots may increase the stability of the bilayer over time and improve its capacitative properties, lipid encapsulation appears to obscure the photoreactive properties of the quantum dots. In the case of gold nanoparticles, the construct is initially stabilized but deteriorates more quickly than those SUVs containing quantum dots, as evidenced by an increase in substrate diffusion. Additionally, although these constructs are more photoreactive than those containing QDs, the increase in absorbance is observed primarily in a range below that of the visible spectrum, a feature which is of limited use for the proposed application. Further studies should investigate alternative methods of nanoparticle capping to improve stability and absorbance in this system.

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Date Created
  • 2015-05

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Hydrogel Nanosensors for Colorimetric Detection and Dosimetry in Proton Beam Radiotherapy

Description

Proton beam therapy (PBT) is a state-of-the-art radiotherapy treatment approach that uses focused proton beams for tumor ablation. A key advantage of this approach over conventional photon radiotherapy (XRT) is

Proton beam therapy (PBT) is a state-of-the-art radiotherapy treatment approach that uses focused proton beams for tumor ablation. A key advantage of this approach over conventional photon radiotherapy (XRT) is the unique dose deposition characteristics of protons, resulting in superior healthy tissue sparing. This results in fewer unwanted side effects and improved outcomes for patients. Current available dosimeters are intrinsic, complex and expensive; hence cannot be used to determine the dose delivered to the tumor routinely. Here, we report a hydrogel based plasmonic nanosensor for measurements of clinical doses in ranges between 2-4 GyRBE. In this nanosensor, gold ions, encapsulated in a hydrogel, are reduced to gold nanoparticles following irradiation with proton beams. Formation of gold nanoparticles renders a color change to the originally colorless hydrogel. The intensity of the color can be used to calibrate the hydrogel nanosensor in order to quantify different radiation doses employed during treatment. The potential of this nanosensor for clinical translation was demonstrated using an anthropomorphic phantom mimicking a clinical radiotherapy session. The simplicity of fabrication, detection range in the fractionated radiotherapy regime and ease of detection with translational potential makes this a first-in-kind plasmonic colorimetric nanosensor for applications in clinical proton beam therapy.

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Created

Date Created
  • 2017

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Poly(amino ether) based Polymeric and Nanoparticle Systems for Nucleic Acid Delivery and Bioimaging

Description

Gold nanoparticles have emerged as promising nanomaterials for biosensing, imaging, photothermal treatment and therapeutic delivery for several diseases, including cancer. We have generated poly(amino ether)-functionalized gold nanorods (PAE-GNRs) using a

Gold nanoparticles have emerged as promising nanomaterials for biosensing, imaging, photothermal treatment and therapeutic delivery for several diseases, including cancer. We have generated poly(amino ether)-functionalized gold nanorods (PAE-GNRs) using a layer-by-layer deposition approach. Sub-toxic concentrations of PAE-GNRs were employed to deliver plasmid DNA to prostate cancer cells in vitro. PAE-GNRs generated using 1,4C-1,4Bis, a cationic polymer from our laboratory demonstrated significantly higher transgene expression and exhibited lower cytotoxicities when compared to similar assemblies generated using 25 kDa poly(ethylene imine) (PEI25k-GNRs), a current standard for polymer-mediated gene delivery. Additionally, sub-toxic concentrations of 1,4C-1,4Bis-GNR nanoassemblies were employed to deliver expression vectors that express shRNA ('shRNA plasmid') against firefly luciferase gene in order to knock down expression of the protein constitutively expressed in prostate cancer cells. The roles of poly(amino ether) chemistry and zeta-potential in determining transgene expression efficacies of PAE-GNR assemblies were investigated. The theranostic potential of 1,4C-1,4Bis-GNR nanoassemblies was demonstrated using live cell two-photon induced luminescence bioimaging. The PAE class of polymers was also investigated for the one pot synthesis of both gold and silver nanoparticles using a small library poly(amino ethers) derived from linear-like polyamines. Efficient nanoparticle synthesis dependent on concentration of polymers as well as polymer chemical composition is demonstrated. Additionally, the application of poly(amino ether)-gold nanoparticles for transgene delivery is demonstrated in 22Rv1 and MB49 cancer cell lines. Base polymer, 1,4C-1,4Bis and 1,4C-1,4Bis templated and modified gold nanoparticles were compared for transgene delivery efficacies. Differences in morphology and physiochemical properties were investigated as they relate to differences in transgene delivery efficacy. There were found to be minimal differences suggestion that 1,4C-1,4Bis efficacy is not lost following use for nanoparticle modification. These results indicate that poly(amino ether)-gold nanoassemblies are a promising theranostic platform for delivery of therapeutic payloads capable of simultaneous gene silencing and bioimaging.

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Created

Date Created
  • 2014

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Artificial phototropism based on a photo-thermo-responsive hydrogel

Description

Solar energy is leading in renewable energy sources and the aspects surrounding the efforts to harvest light are gaining importance. One such aspect is increasing the light absorption, where heliotropism

Solar energy is leading in renewable energy sources and the aspects surrounding the efforts to harvest light are gaining importance. One such aspect is increasing the light absorption, where heliotropism comes into play. Heliotropism, the ability to track the sun across the sky, can be integrated with solar cells for more efficient photon collection and other optoelectronic systems. Inspired by plants, which optimize incident sunlight in nature, several researchers have made artificial heliotropic and phototropic systems. This project aims to design, synthesize and characterize a material system and evaluate its application in a phototropic system. A gold nanoparticle (Au NP) incorporated poly(N-isopropylacrylamide) (PNIPAAm) hydrogel was synthesized as a photo-thermo-responsive material in our phototropic system. The Au NPs generate heat from the incident via plasmonic resonance to induce a volume phase change of the thermo-responsive hydrogel PNIPAAm. PNIPAAm shrinks or swells at temperature above or below 32°C. Upon irradiation, the Au NP-PNIPAAm micropillar actuates, specifically bending toward the incident light and precisely following the varying incident angle.

Swelling ratio tests, bending angle tests with a static incident light and bending tests with varying angles were carried out on hydrogel samples with varying Au NP concentrations. Swelling ratios ranging from 1.45 to 2.9 were recorded for pure hydrogel samples and samples with very low Au NP concentrations. Swelling ratios of 2.41 and 3.37 were calculated for samples with low and high concentrations of Au NPs, respectively. A bending of up to 88° was observed in Au NP-hydrogel pillars with a low Au NP concentration with a 90° incident angle. The light tracking performance was assessed by the slope of the pillar Bending angle (response angle) vs. Incident light angle plot. A slope of 1 indicates ideal tracking with top of the pillar being normal to the incident light, maximizing the photon absorption. Slopes of 0.82 and 0.56 were observed for the low and high Au NP concentration samples. The rapid and precise incident light tracking of our system has shown the promise in phototropic applications.

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Date Created
  • 2016

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Rapid and cost-effective virus detection methods using molecular sensors and nano-devices

Description

Accurate virus detection is important for diagnosis in a timely manner to facilitate rapid interventions and treatments. RNA viruses affect an extensive amount of the world’s population, particularly in tropical

Accurate virus detection is important for diagnosis in a timely manner to facilitate rapid interventions and treatments. RNA viruses affect an extensive amount of the world’s population, particularly in tropical countries where emerging infectious agents often arise. Current diagnostic methods have three main problems: they are time consuming, typically not field-portable, and expensive. My research goal is to develop rapid, field-portable and cost sensitive diagnostic methods for RNA viruses. Herein, two different approaches to detect RNA viruses were proposed: Conjugated gold nanoparticles for detection of viral particles or virus-specific antibodies by monitoring changes in their optical properties, and Tentacle Probes coupled with qPCR for detection and differentiation of closely-related viral strains. The first approach was divided into two projects: the study and characterization of the gold nanoparticle-antibody system for detection of virus particles using dynamic light scattering (DLS) and UV-Vis spectrophotometry, and development of a detection method for antibodies using static light scattering (SLS) and antigen-conjugated gold nanoparticles. Bovine serum albumin (BSA) conjugated gold nanoparticles could successfully detect BSA-specific antibodies in vitro, and protein E from Dengue Virus serotype 2 conjugated gold nanoparticles could detect Dengue-specific antibodies, both in vitro and in serum samples. This method is more accurate than currently used detection methods such as dot blots. The second approach uses Tentacle Probes, which are modified molecular beacons, to detect with high specificity two different strains of Lymphocytic Choriomeningitis Virus (LCMV), Armstrong and Clone-13, which differ in only one nucleotide at the target sequence. We successfully designed and use Tentacle Probes for detection of both strains of LCMV, in vitro and in serum from infected mice. Moreover, detection of as little as 10% of Clone-13 strain was possible when diluted in 90% Armstrong strain. This approach enables the detection of different strains of virus even within a mixed quasispecies and may be important for improving intervention strategies for reducing disease. The detection methods provide rapid detection of viruses, including viral strains within mixed populations, and should enhance our ability in providing early responses to emerging infectious diseases due to RNA viruses including Zika or Dengue virus.

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Date Created
  • 2016