Matching Items (38)

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Stimuli-Responsive Polymers: Design, Synthesis, Characterization, and Applications

Description

Stimuli-responsive polymers or so-called “smart polymers” are macromolecules that are sensitive to certain triggers from the external environment, including temperature, light, electrical or magnetic fields, and chemicals. The activated polymers

Stimuli-responsive polymers or so-called “smart polymers” are macromolecules that are sensitive to certain triggers from the external environment, including temperature, light, electrical or magnetic fields, and chemicals. The activated polymers produce observable or detectable micro- or nanoscale changes, such as morphology, molecular bond rearrangement/cleavage, and molecular motion, which can induce changes in their macroscopic properties such as color, shape, and functionality. Due to the versatile selection of backbone and functional groups, stimuli-responsive polymers can be tailored to have a variety of specific mechanical, chemical, electrical, optical, biological, or other properties and can be engineered into different forms, including bulk, thin film, micro
anoparticles, and composites. Over the years, many multidisciplinary efforts have been conducted and reported optimizing the functionality of stimuli-responsive polymers and exploring new and innovative applications. However, as shown below, original and exciting research in emerging sectors continues to drive the evolution of and interest in this class of polymer.

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  • 2016-07-05

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Polymeric Micelle Characterization and Stability for Drug Delivery Systems

Description

The current methods of drug delivery prove to have inefficiencies as far as drug administration to the target site. Due to adverse factors that the drug faces within the body,

The current methods of drug delivery prove to have inefficiencies as far as drug administration to the target site. Due to adverse factors that the drug faces within the body, it can be broken down before the therapeutic can be applied. Polymeric micelles have shown promising results in the face of these circumstances, by being able to self-assemble into a core-shell structure to better house the medicine as it travels through blood stream upon intravenous injection. The triblock copolymer, PEG-PPG-PEG, uses it hydrophilic and hydrophobic components to form a spherical micelle at a nanoscale size allowing it cross barriers with greater ease and prolong dissociation. The resulting size of the micelle is measured by the use of a dynamic light scattering machine. Stability factors, such as, thermodynamic and kinetic stability, also aid in the formation of micelles, but are generally effected in drug delivery process by factors such as salt concentration and pH. Both these factors can cause a lack of stability resulting in aggregation of the micelles; therefore, their affects need to be prolonged in order to have sufficient drug delivery.

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  • 2017-05

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Electrospinning Stimuli-Responsive Fibers at the Nanoscale as Functional Drug Delivery Mats

Description

The objective of this research is to create biodegradable mats with tunable characteristics such as fiber diameter and surface area. The drug delivery mats enable spatially controlled delivery of

The objective of this research is to create biodegradable mats with tunable characteristics such as fiber diameter and surface area. The drug delivery mats enable spatially controlled delivery of disease-specific therapeutics. Using a large electric potential to draw fibers from a solution flowing at a specific rate, the polymer fibers reach a grounded target several inches away. The biodegradable polymer used in this study was poly(lactic acid-co-glycolic acid) (PLGA). PLGA solutions ranging from 0.5 to 27 wt.% were prepared by dissolving the block copolymer in a solvent mixture containing tetrahydrofuran (THF) and dimethylformamide (DMF) at a 3:1 weight ratio. They were then electrospun at needle-to-target distances of 7, 14, and 18 cm and rates ranging from 0.8 to 4 mL/h. The range of voltage used was between 8 – 15 kV, which was based on the observation of the formation of a Taylor cone, largely affected by on the environment and weather (e.g., temperature and humidity in the lab). A 27 wt.% PLGA solution, electrospun at 1 mL/h at a voltage of 11.25 kV and needle-to-target distance of 14 cm produced uniform fibers with an average fiber diameter of 0.985 m. All other parameters outside the range given created beaded fibers. In addition, solution rheology was performed on some of the PLGA solution to measure viscosity, which is directly correlated to the fiber diameter of the electrospun mats. Observing the impact of solvent on fiber spinning and fiber diameter brings about many positive results in developing fully characterized and well-understood fibrous mats for drug delivery. The nanoscale fibers will be used as drug delivery mats and, therefore, the biodegradation kinetics of the polymers will be studied. Next, parameters of the polymers as well as the polymeric mats will be correlated to the degradation-mediated release of small molecule therapeutics (e.g., peptides, drugs, etc.) such that time-resolved dosing profiles can be created.

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  • 2016-12

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Methods to Enhance Overexpression of Membrane Protein in Escherichia coli

Description

Membrane proteins (MPs) are an important aspect of cell survival that ensure structural integrity, signaling, and transportation of molecules. Since 2015, over 450 MPs have been studied to find their

Membrane proteins (MPs) are an important aspect of cell survival that ensure structural integrity, signaling, and transportation of molecules. Since 2015, over 450 MPs have been studied to find their functionalities and structure. Sufficient amounts of correctly folded MPs are needed to accurately study them through crystallography and other structural study methods. Use of recombinant technology is needed to overexpress MPs as natural abundance of MP is often too slow to provide the necessary amounts. However, an increase in toxicity and decrease in generation time deter the overexpression of MPs. The following report discusses two methods of enhancing overexpression in Escherchia coli, the use of T7 RNA polymerase (T7RNAP) and the reprogramming of chaperon pathways, that combats toxicity and promotes cell growth. Overall, both methods are proven to work effectively to overexpress MPs by regulating transcription rate of mRNA (T7RNAP) or folding and transporting of polypeptides to inner membrane (chaperon pathway). To further study the effectiveness of the two methods, they will need to be compared at the same conditions. In addition, a combination of two methods should also be studied to find out if the combination would have a great impact on the overexpression of the MPs.

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  • 2018-05

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Targeting Tumors: Inclusion of Functional Groups on Ion-Containing Block Copolymers to Combat Cancer

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This research attempts to determine the most effective method of synthesizing a peptide such that it can be utilized as a targeting moiety for polymeric micelles. Two melanoma-associated peptides with

This research attempts to determine the most effective method of synthesizing a peptide such that it can be utilized as a targeting moiety for polymeric micelles. Two melanoma-associated peptides with high in vitro and in vivo binding affinity for TNF receptors have been identified and synthesized. Matrix Assisted Laser Desorption/Ionization-Time of Flight Mass Spectrometry (MALDI-ToF) was used to help verify the structure of both peptides, which were purified using Reversed-Phase High Performance Liquid Chromatography (RP-HPLC). The next steps in the research are to attach the peptides to a micelle and determine their impact on micelle stability.

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  • 2016-05

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Nanostructured Faujasite Zeolites for Carbon Dioxide Adsorption: Adsorption Equilibrium and Dynamics Modeling

Description

Carbon capture is an essential way to reduce greenhouse gas emissions. One way to decrease the emissions is through the use of adsorbents such as zeolites. Dr. Dong-Kyun Seo’s grou

Carbon capture is an essential way to reduce greenhouse gas emissions. One way to decrease the emissions is through the use of adsorbents such as zeolites. Dr. Dong-Kyun Seo’s group (School of Molecular Sciences, Arizona State University) synthesized the nanostructured faujasite (NaX). The zeolite was characterized using Scanning Electron Microscopy (SEM) and the physisorption properties were determined using ASAP 2020. ASAP 2020 tests of the nano-zeolite pellets at 77K in a liquid N2 bath determined the BET surface area of 547.1 m2/mol, T-plot micropore volume of 0.2257 cm3/g, and an adsorption average pore width of 5.9 Å. The adsorption isotherm (equilibrium) of CH4, N2, and CO2 were measured at 25ºC. Adsorption isotherm experiments concluded that the linear isotherm was the best fit for N2, and CH4 and the Sips isotherm was a better fit than the Langmuir and Freundlich isotherm for CO2. At 25ºC and 1 atm the zeolite capacity for CO2 is 4.3339 mmol/g, 0.1948 mmol/g for CH4, and 0.3534 mmol/g for N2. The zeolite has a higher CO2 capacity than the conventional NaX zeolite. Breakthrough experiments were performed in a fixed bed 22in, 0.5 in packing height and width at 1 atm and 298 K with nano-zeolite pellets. The gas chromatographer tested and recorded the data every two minutes with a flow rate of 10 cm3/min for N2 and 10 cm3/min CO2. Breakthrough simulations of the zeolite in a fixed bed adsorber column were conducted on MATLAB utilizing varying pressures, flow rates, and fed ratios of various CO2, N2 and CH4. Simulations using ideal adsorbed solution theory (IAST) calculations determined that the selectivity of CO2 in flue gas (15% CO2 + 85% N2) is 571.79 at 1 MPa, significantly higher than commercial zeolites and literature. The nanostructured faujasite zeolite appears to be a very promising adsorbent for CO2/N2 capture from flue gas and the separation of CO2/N2.

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  • 2018-05

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Protein-mediated Synthesis of Gold Nanoparticles

Description

Gold nanoparticles are valuable for their distinct properties and nanotechnology applications. Because their properties are controlled in part by nanoparticle size, manipulation of synthesis method is vital, since the chosen

Gold nanoparticles are valuable for their distinct properties and nanotechnology applications. Because their properties are controlled in part by nanoparticle size, manipulation of synthesis method is vital, since the chosen synthesis method has a significant effect on nanoparticle size. By aiding mediating synthesis with proteins, unique nanoparticle structures can form, which open new possibilities for potential applications. Furthermore, protein-mediated synthesis favors conditions that are more environmentally and biologically friendly than traditional synthesis methods. Thus far, gold particles have been synthesized through mediation with jack bean urease (JBU) and para mercaptobenzoic acid (p-MBA). Nanoparticles synthesized with JBU were 80-90nm diameter in size, while those mediated by p-MBA were revealed by TEM to have a size between 1-3 nm, which was consistent with the expectation based on the black-red color of solution. Future trials will feature replacement of p-MBA by amino acids of similar structure, followed by peptides containing similarly structured amino acids.

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  • 2018-05

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Utilizing Magnetic Electrospinning to Create Gradients in Fiber Alignment for Interfacial Tissue Engineering

Description

Heterogeneous tissues are composed of chemical and physical gradients responsible for transferring load from one tissue type to another, through the thickness or the length of the tissue. Musculoskeletal tissues

Heterogeneous tissues are composed of chemical and physical gradients responsible for transferring load from one tissue type to another, through the thickness or the length of the tissue. Musculoskeletal tissues include these junctions, such as the tendon-bone and ligament-bone, which consist of an alignment gradient through the length of the interfacial regions. These junctions are imperative for transferring mechanical loadings between dissimilar tissues. Engineering a proper scaffold that mimics the native architecture of these tissues to prompt proper repair after an interfacial injury has been difficult to fabricate within tissue engineering. Electrospinning is a common technique for fabricating nanofibrous scaffolds that can mimic the structure of the native extracellular matrix (ECM). However, current electrospinning techniques do not easily allow for the replication of the chemical and physical gradients present in musculoskeletal interfacial tissues. In this work, a novel magnetic electrospinning technique was developed to fabricate polycaprolactone (PCL) nanofibrous scaffolds that recapitulate the gradient alignment structure of the tendon-bone junction. When exposed to the natural magnetic field from a permanent magnet, PCL fibers innately aligned near the magnet with unalignment at distances further away from the magnetic field.

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  • 2018-05

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The Key to a Happier Thanksgiving: A Study on the Intricacies of Turkey Preparation

Description

The process of cooking a turkey is a yearly task that families undertake in order to deliver a delicious centerpiece to a Thanksgiving meal. While other dishes accompany and comprise

The process of cooking a turkey is a yearly task that families undertake in order to deliver a delicious centerpiece to a Thanksgiving meal. While other dishes accompany and comprise the traditional Thanksgiving supper, focusing on creating a turkey that satisfies the tastes of all guests is difficult, as preferences vary. Over the years, many cooking methods and preparation variations have come to light. This thesis studies these cooking methods and preparation variations, as well as the effects on the crispiness of the skin, the juiciness of the meat, the tenderness of the meat, and the overall taste, to simplify the choices that home cooks have to prepare a turkey that best fits their tastes. Testing and evaluation reveal that among deep-frying, grilling, and oven roasting turkey, a number of preparation variations show statistically significant changes relative to a lack of these preparation variations. For crispiness, fried turkeys are statistically superior, scoring about 1.5 points higher than other cooking methods on a 5 point scale. For juiciness, the best preparation variation was using an oven bag, with the oven roasted turkey scoring about 4.5 points on a 5 point scale. For tenderness, multiple methods are excellent, with the best three preparation variations in order being spatchcocking, brining, and using an oven bag, each of these preparation variations are just under a 4 out of 5. Finally, testing reaffirms that judges tend to have different subjective tastes, with some having different perceptions and opinions on some criteria, while statistically agreeing on others: there was 67% agreement among judges on crispiness and tenderness, while there was only 17% agreement on juiciness. Evaluation of these cooking methods, as well as their respective preparation variations, addresses the question of which methods are worthwhile endeavors for cooks.

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  • 2020-05

Fabrication of Alignment and Chemical Gradient Scaffold for Tendon-Bone Repair using Electrospinning

Description

Heterogeneous musculoskeletal tissues, such as the tendon-bone junction, is crucial for transferring mechanical loading during human physical activity. This region, also known as the enthesis, is composed of a complex

Heterogeneous musculoskeletal tissues, such as the tendon-bone junction, is crucial for transferring mechanical loading during human physical activity. This region, also known as the enthesis, is composed of a complex extracellular matrix with gradient fiber orientations and chemistries. These different physical and chemical properties are crucial in providing the support that these junctions need in handling mechanical loading of everyday activities. Currently, surgical restorative procedures for a torn enthesis entail a very invasive technique of suturing the torn tendon onto the bone. This results in improper reinjury. To circumvent this issue, one common strategy within tissue engineering is to introduce a biomaterial scaffold which acts as a template for the local damaged tissue. Electrospinning can be utilized to fabricate a fibrous material to recapitulate the structure of the extracellular matrix. Currently electrospinning techniques only allow the creation of scaffold that consists of only one orientation and material. In this work, we investigated a multicomponent, magnetically assisted, electrospinning technique to fabricate a fiber alignment and chemical gradient scaffold for tendon-bone repair

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  • 2018-05