Current Search: polyelectrolyte (x)
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(1 - 8 of 8)
- Title
- Fabrication of Polyelectrolyte Nanoparticles Through Hydrophobic Interaction.
- Creator
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Catarata, Ruginn Porce, Zhai, Lei, Kang, Ellen, Huo, Qun, University of Central Florida
- Abstract / Description
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Anticancer drugs like gemcitabine (GEM) are used to treat cancers such as, pancreatic ductal adenocarcinoma (PDAC). However, the use of free gemcitabine yields challenges including cytotoxicity to healthy cells and poor circulation time. By encapsulating GEM in nanoparticles these challenges can be overcome. In this study poly(acrylic acid) (PAA)-GEM nanoparticles are fabricated by coupling GEM onto PAA. The particle formation is driven by the hydrophobic interaction of GEM, which collects in...
Show moreAnticancer drugs like gemcitabine (GEM) are used to treat cancers such as, pancreatic ductal adenocarcinoma (PDAC). However, the use of free gemcitabine yields challenges including cytotoxicity to healthy cells and poor circulation time. By encapsulating GEM in nanoparticles these challenges can be overcome. In this study poly(acrylic acid) (PAA)-GEM nanoparticles are fabricated by coupling GEM onto PAA. The particle formation is driven by the hydrophobic interaction of GEM, which collects in the core of the nanoparticle, forming a PAA shell. The nanoparticles were optimized by studying the PAA/GEM ratio and pH during fabrication. Characteristics of the nanoparticles including size, morphology and surface charge were investigated using dynamic light scattering (DLS), transmission electron microscopy (TEM) and zeta potential measurements. Conditions such as ionic stability and pH stability were optimized to achieve high drug loading efficiency. Cell uptake and cytotoxicity studies were used to determine the efficiency of the nanoparticles as drug delivery vehicle.
Show less - Date Issued
- 2019
- Identifier
- CFE0007791, ucf:52364
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007791
- Title
- Multifunctional and Responsive Polyelectrolyte Nanostructures.
- Creator
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Malhotra, Astha, Zhai, Lei, Kolpashchikov, Dmitry, Ye, Jingdong, Chumbimuni Torres, Karin, Santra, Swadeshmukul, Fang, Jiyu, University of Central Florida
- Abstract / Description
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A polyelectrolyte complex is formed by mixing two oppositely charged polyelectrolytes in a solution. The electrostatic interactions between partially charged polymeric chains lead to the formation of a stable complex while avoiding the use of covalent cross linkers. Since complex formation can improve the stability of polyelectrolyte and metal ions in polyelectrolyte can provide various functionalities, PECs incorporated with metal ions are promising candidates for manufacturing stable and...
Show moreA polyelectrolyte complex is formed by mixing two oppositely charged polyelectrolytes in a solution. The electrostatic interactions between partially charged polymeric chains lead to the formation of a stable complex while avoiding the use of covalent cross linkers. Since complex formation can improve the stability of polyelectrolyte and metal ions in polyelectrolyte can provide various functionalities, PECs incorporated with metal ions are promising candidates for manufacturing stable and multifunctional structures. While the coordination of metal ions and polyelectrolytes has been extensively investigated in solutions and multilayer films, to our knowledge, no research has been performed to study the effect of metal ion/polyelectrolyte interactions on PECs structures and properties. The following research demonstrates the impact of different metal ions in controlling PEC structure morphology and applications. These discoveries indicate great potential of metal ions in PECs to fabricate functional PEC nanostructures.The research investigates the effect of the interactions between different metal ions and polyelectrolytes on the morphology and properties of PECs, explore the fabrication of different structures using embedded metal ions and understand the impact of metal ion/polyelectrolyte interactions on the nanoparticle structures. The research concludes: 1) incorporating metal ions of different valence into PECs introduces metal ion/polyelectrolyte interactions that can tune the morphology of PECs; 2) metal ion/polyelectrolyte interactions can be used to control the PECs swelling properties and stability in aqueous solutions; 3) the release of embedded metal ions from PECs to aqueous solutions is affected by metal ion/polyelectrolyte interactions; and 4) the embedded metal ions function as a reagent reservoir for various applications to produce functional structures. ?
Show less - Date Issued
- 2014
- Identifier
- CFE0005833, ucf:50918
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0005833
- Title
- Polyelectrolyte complexes based on poly(acrylic acid): mechanics and applications.
- Creator
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Lu, Xiaoyan, Zhai, Lei, Zou, Shengli, Chumbimuni Torres, Karin, Kolpashchikov, Dmitry, Dong, Yajie, University of Central Florida
- Abstract / Description
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Poly(acrylic acid) (PAA) is a weak polyelectrolyte presenting negative charge at basic conditionwhen the carboxylic group loses a proton. These carboxylate group can interact with polycationsand metal ions to form stable polyelectrolyte complexes (PECs), leading to tunable propertiesand multifunctional nanoscale structures through chemical reactions. This research focuses onnanofiber and nanoparticle fabricated by PAA-based PECs. We demonstrated the effect of ferricion concentration on the...
Show morePoly(acrylic acid) (PAA) is a weak polyelectrolyte presenting negative charge at basic conditionwhen the carboxylic group loses a proton. These carboxylate group can interact with polycationsand metal ions to form stable polyelectrolyte complexes (PECs), leading to tunable propertiesand multifunctional nanoscale structures through chemical reactions. This research focuses onnanofiber and nanoparticle fabricated by PAA-based PECs. We demonstrated the effect of ferricion concentration on the mechanical properties of PAA-based single naonofiber by using dark fieldmicroscopy imaging and persistence length analysis. The application of PAA-based nanofibermats loaded with MnO2 for supercapacitors was also explored. As a free-standing and flexiblesupercapacitor electrode, the nanofiber mat exhibited outstanding properties including high specificcapacitance, excellent reversible redox reactions, and fast charge/discharge ability. Since PAA is abiocompatible polymer, PAA-based PEC was applied as a drug-carrier in a drug delivery system.In this project, core-shell nanoparticles were fabricated with chitosan as the core and PAA as theshell to incorporate with the drug gemcitabine. Several parameters were investigated to obtainthe optimal nanoparticle size. The as-prepared drug delivery system shows prolonged releasingprofile.
Show less - Date Issued
- 2018
- Identifier
- CFE0007045, ucf:52004
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007045
- Title
- SELF-ASSEMBLY AND PHOTOPHYSICS OF SELECTED ORGANIC MATERIALS AND TWO-PHOTON BIOIMAGING WITH PROFLUORESCENT NITROXIDES, POLYELECTROLYTE NANOPARTICLES, AND SQUARAINE PROBES.
- Creator
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Ahn, Hyo-Yang, Belfield, Kevin, University of Central Florida
- Abstract / Description
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Two-photon absorption and upconverted fluorescence has been utilized in a variety of applications in pure science and engineering. Multiphoton-based techniques were used in this research in order to understand photophysical and chemical characteristics of several fluorescent dyes and to demonstrate some of their key applications. Two-photon fluorescence microscopy (2PFM) has become a powerful technique in bio-photonics for non-invasive imaging in the near-infrared (NIR) region (700~1000 nm)...
Show moreTwo-photon absorption and upconverted fluorescence has been utilized in a variety of applications in pure science and engineering. Multiphoton-based techniques were used in this research in order to understand photophysical and chemical characteristics of several fluorescent dyes and to demonstrate some of their key applications. Two-photon fluorescence microscopy (2PFM) has become a powerful technique in bio-photonics for non-invasive imaging in the near-infrared (NIR) region (700~1000 nm) that often results in less photobleaching. In Chapter 1, there is a brief introduction to fluorescence, examples of fluorescence materials, and a discussion of the advantages of two-photon absorption. 2PFM imaging was utilized in Chapters 2 to 4 for various applications. In Chapter 2, a new squaraine dye is introduced and its linear and nonlinear photophysical properties are characterized. This compound has very high two-photon absorption (2PA) cross sections and high photostability both in an organic solvent and when encapsulated in micelles. Based on these properties, this dye was demonstrated as a near-infrared (NIR) probe in in vitro 2PFM imaging with excitation over 800 nm wavelength. In Chapter 3, new profluorescent nitroxides are introduced. Nitroxide radicals are utilized for electron paramagnetic resonance (EPR) spectroscopy and in biological systems as some are known, in some manner, to mimic the behavior of superoxide dismutase (SOD) that detoxifies or mitigates oxidative stress by trapping free radicals. Here, two profluorescent nitroxides investigated for use as a two-photon fluorescent oxidative stress indicator in in vitro two-photon fluorescence microscopy (2PFM) imaging. In Chapter 4, two-photon excited (2PE) fluorescence of a conjugated polyelectrolyte (CPE), PPESO3, was studied in methanol and in water. The results of CPE quenching studies were comparable under both one-photon excitation conditions and two-photon excitation. CPE coated silica nanoparticles were incubated in HeLa cells and 2PFM imaging was demonstrated for this new class of fluorescent probe. Supramolecular structures based on organized assemblies/aggregation of chromophores have attracted widespread interest as molecular devices with potential applications in molecular electronics, artificial light harvesting, and pharmacology. In Chapter 5, J-aggregate formation was investigated for two porphyrin-based dyes, 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin (TPPS, 4) and an amino tris-sulfonate analog (5) in water via UV-vis, fluorescence, and lifetime decay studies. The effect of aggregation on two-photon absorption properties was also investigated. A functionalized norbornene-based homopolymer, synthesized by the ring opening metathesis polymerization technique was used as a J-aggregation enhancement template and had a role of polymer-templating to facilitate porphyrin aggregation and modulate 2PA. In Chapter 6, squaraine dye aggregates templated with single wall carbon nanotubes (SWCNTs) that were atomically clean were studied by using optical absorption spectroscopy, atomic force microscopy (AFM), and photoconductivity measurements. SWCNTs selectively promote the formation of squaraine dye aggregates with a head-to-head stacking arrangement, and these dye aggregates effectively photosensitize SWCNTs, demonstrating that this novel approach can yield highly photosensitized devices.
Show less - Date Issued
- 2011
- Identifier
- CFE0003978, ucf:48665
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0003978
- Title
- Mechanism of Actin Bundle Assembly, Mechanics and Structure by Ion Interaction.
- Creator
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Castaneda, Nicholas, Kang, Hyeran, Huo, Qun, Gesquiere, Andre, University of Central Florida
- Abstract / Description
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The assembly of actin filaments into bundles plays an essential role in mechanical strength and dynamic reorganization of cytoskeleton. Divalent counterions at high concentrations promote bundle formation through electrostatic attraction between charged filaments. Although it has been hypothesized that specific cation interactions may contribute to salt-induced bundling, molecular mechanisms of how salt modulates bundle assembly and mechanics are not well established. Here we determine the...
Show moreThe assembly of actin filaments into bundles plays an essential role in mechanical strength and dynamic reorganization of cytoskeleton. Divalent counterions at high concentrations promote bundle formation through electrostatic attraction between charged filaments. Although it has been hypothesized that specific cation interactions may contribute to salt-induced bundling, molecular mechanisms of how salt modulates bundle assembly and mechanics are not well established. Here we determine the mechanical and dynamic properties of actin bundles with physiologically relevant cations. Using total internal reflection fluorescence (TIRF) microscopy, we measure the bending stiffness of actin bundles determined by persistence length analysis. We characterize real-time formation of bundles by dynamic light scattering intensity and direct visualization using TIRF microscopy. Our results show that divalent cations modulate bundle stiffness as well as time-dependent average bundle size. Furthermore, molecular dynamic simulations propose specificity for cation binding on actin filaments to form bundles. The work suggests that cation interactions serve a regulatory function in bundle assembly dynamics, mechanics, and structure.
Show less - Date Issued
- 2017
- Identifier
- CFE0006572, ucf:51307
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006572
- Title
- Tunable Effect of Metal Ions on Polyelectrolyte Mechanics.
- Creator
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Diaz, Angie, Kang, Hyeran, Zhai, Lei, Tetard, Laurene, University of Central Florida
- Abstract / Description
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Polyelectrolyte based hydrogel fibers can mimic extracellular matrix and have applications such as drug delivery and tissue scaffolding. Metal ions play a critical role in hydrogel fiber stability via electrostatic interactions, but knowledge of how they modulate mechanical properties of individual polyelectrolyte polymers is lacking. In this study, electrospun polyacrylic acid with chitosan is used as a model system to evaluate ferric ion effect on nanofiber mechanics. Using dark field...
Show morePolyelectrolyte based hydrogel fibers can mimic extracellular matrix and have applications such as drug delivery and tissue scaffolding. Metal ions play a critical role in hydrogel fiber stability via electrostatic interactions, but knowledge of how they modulate mechanical properties of individual polyelectrolyte polymers is lacking. In this study, electrospun polyacrylic acid with chitosan is used as a model system to evaluate ferric ion effect on nanofiber mechanics. Using dark field microscopy imaging and persistence length analysis, we demonstrate that ferric ions modulate the bending stiffness of nanofibers. Young's modulus of individual nanofibers is estimated at values of a few kilopascals, suggesting that electrospun nanofibers possibly exist in a hydrated state. Furthermore, Fourier Transform Infrared (FTIR) spectra indicate the effect of ferric ions on polyacrylic acid molecular bonds. Our results suggest that metal ions can regulate single nanofiber stiffness, thereby providing designs to fabricate hydrogels in a tunable fashion.
Show less - Date Issued
- 2018
- Identifier
- CFE0006993, ucf:51625
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006993
- Title
- APPLICATION OF POLYELECTROLYTE MULTILAYERS FOR PHOTOLITHOGRAPHIC PATTERNING OF DIVERSE MAMMALIAN CELL TYPES IN SERUM FREE MEDIUM.
- Creator
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Dhir, Vipra, Cho, Hyoung Jin, University of Central Florida
- Abstract / Description
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Integration of living cells with novel microdevices requires the development of innovative technologies for manipulating cells. Chemical surface patterning has been proven as an effective method to control the attachment and growth of diverse cell populations. Patterning polyelectrolyte multilayers through the combination of layer-by-layer self-assembly technique and photolithography offers a simple, versatile and silicon compatible approach that overcomes chemical surface patterning...
Show moreIntegration of living cells with novel microdevices requires the development of innovative technologies for manipulating cells. Chemical surface patterning has been proven as an effective method to control the attachment and growth of diverse cell populations. Patterning polyelectrolyte multilayers through the combination of layer-by-layer self-assembly technique and photolithography offers a simple, versatile and silicon compatible approach that overcomes chemical surface patterning limitations, such as short-term stability and low protein adsorption resistance. In this study, direct photolithographic patterning of PAA/PAAm and PAA/PAH polyelectrolyte multilayers was developed to pattern mammalian neuronal, skeletal and cardiac muscle cells. For all studied cell types, PAA/PAAm multilayers behaved as a negative surface, completely preventing cell attachment. In contrast, PAA/PAH multilayers have shown a cell-selective behavior, promoting the attachment and growth of neuronal cells (embryonic rat hippocampal and NG108-15 cells) to a greater extent, while providing a little attachment for neonatal rat cardiac and skeletal muscle cells (C2C12 cell line). PAA/PAAm multilayer cellular patterns have also shown a remarkable protein adsorption resistance. Protein adsorption protocols commonly used for surface treatment in cell culture did not compromise the cell attachment inhibiting feature of the PAA/PAAm multilayer patterns. The combination of polyelectrolyte multilayer patterns with different adsorbed proteins could expand the applicability of this technology to cell types that require specific proteins either on the surface or in the medium for attachment or differentiation, and could not be patterned using the traditional methods.
Show less - Date Issued
- 2008
- Identifier
- CFE0002357, ucf:47783
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0002357
- Title
- Influence of Chitosan-Alginate Scaffold Stiffness on Bone Marrow Stromal Cell Differentiation.
- Creator
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Arias Ponce, Isabel, Florczyk, Stephen, Fang, Jiyu, Khaled, Annette, Leon, Lorraine, University of Central Florida
- Abstract / Description
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Tissue grafts are the gold standard for replacing large volume tissue defects. Yet, they present several risks, including infection, low functional outcomes, and reduced graft integrity. Tissue engineering (TE) combines cells and biomaterial scaffolds to foster tissue growth and remodeling. Bone marrow stromal cells (BMSCs) have been shown to respond to the stiffness of their microenvironment, resulting in differentiation into different lineages. 3D porous chitosan-alginate (CA) scaffolds...
Show moreTissue grafts are the gold standard for replacing large volume tissue defects. Yet, they present several risks, including infection, low functional outcomes, and reduced graft integrity. Tissue engineering (TE) combines cells and biomaterial scaffolds to foster tissue growth and remodeling. Bone marrow stromal cells (BMSCs) have been shown to respond to the stiffness of their microenvironment, resulting in differentiation into different lineages. 3D porous chitosan-alginate (CA) scaffolds have been previously demonstrated for bone TE with osteoblasts and BMSCs; however, only a single scaffold composition (4 wt%) was studied. Three CA scaffold compositions (2, 4, 6 wt% CA) were produced. Scanning electron microscopy images were obtained to determine average pore sizes for 2, 4, and 6 wt% CA scaffolds, which were 233, 208, and 146 ?m. Compression testing was performed on CA scaffolds in dry and wet conditions, where higher concentrations yielded higher stiffnesses ranging from 0.22 to 5.34 kPa and 21.1 to 47.3 Pa, respectively. Fourier transform infrared spectroscopy performed on the CA scaffolds confirmed polyelectrolyte complex formation for all compositions. Human BMSCs from three donors were seeded on CA scaffolds, cultured in growth media for 14 days, then cultured in adipogenic or osteogenic differentiation media for 28 days to promote differentiation. Our hypothesis was that scaffold stiffness would influence BMSC differentiation, with softer scaffolds promoting adipogenesis and stiffer scaffolds promoting osteogenesis. BMSCs formed multicellular spheroids in all CA scaffold concentrations, while the 2 wt% CA scaffolds had smaller spheroids compared to the 4 wt% and 6 wt% CA scaffolds. Osteogenic and adipogenic differentiation were evaluated with Alizarin Red and Oil Red O staining, respectively. While positive staining was observed in all scaffold compositions, more robust differentiation was expected, thereby disproving our hypothesis. The polysaccharide composition of the CA scaffolds likely contributed to the spheroid formation and limited differentiation.
Show less - Date Issued
- 2018
- Identifier
- CFE0007389, ucf:52061
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007389
