Current Search: Florczyk, Stephen (x)
View All Items
(1 - 8 of 8)
- Title
- THE INFLUENCE OF 3D POROUS CHITOSAN-ALGINATE BIOMATERIAL SCAFFOLD PROPERTIES ON THE BEHAVIOR OF BREAST CANCER CELLS.
- Creator
-
Le, Minh-Chau N., Steward, Robert L., Florczyk, Stephen J., University of Central Florida
- Abstract / Description
-
The tumor microenvironment plays an important role in regulating cancer cell behavior. The tumor microenvironment describes the cancer cells, and the surrounding endothelial cells, fibroblasts, and mesenchymal stem cells, along with the extracellular matrix (ECM). The tumor microenvironment stiffens as cancer undergoes malignant progression, providing biophysical cues that promote invasive, metastatic cellular behaviors. This project investigated the influence of three dimensional (3D)...
Show moreThe tumor microenvironment plays an important role in regulating cancer cell behavior. The tumor microenvironment describes the cancer cells, and the surrounding endothelial cells, fibroblasts, and mesenchymal stem cells, along with the extracellular matrix (ECM). The tumor microenvironment stiffens as cancer undergoes malignant progression, providing biophysical cues that promote invasive, metastatic cellular behaviors. This project investigated the influence of three dimensional (3D) chitosan-alginate (CA) scaffold stiffness on the morphology, growth, and migration of green fluorescent protein (GFP) � transfected MDA-MB-231 (231-GFP) breast cancer (BCa) cells. The CA scaffolds were produced by the freeze casting method at three concentrations, 2 wt%, 4 wt%, and 6 wt% to provide different stiffness culture substrates. The CA scaffold material properties were characterized using scanning electron microscopy imaging for pore structure and compression testing for Young's Modulus. The BCa cell cultures were characterized at day 1, 3, and 7 timepoints using Alamar Blue assay for cell number, fluorescence imaging for cell morphology, and single-cell tracking for cell migration. Pore size calculations using SEM imaging yielded pore sizes of 253.29 +/- 52.45 [micro]m, 209.55 +/- 21.46 [micro]m, and 216.83 +/- 32.63 [micro]m for 2 wt%, 4 wt%, and 6 wt%, respectively. Compression testing of the CA scaffolds yielded Young's Modulus values of 0.064 +/- 0.008 kPa, 2.365 +/- 0.32 kPa and 3.30 +/- 0.415 kPa for 2 wt%, 4 wt%, and 6 wt% CA scaffolds, respectively. The results showed no significant difference in cell number among the 3D CA scaffold groups. However, the 231-GFP cells cultured in 2 wt% CA scaffolds possessed greater cellular size, area, perimeter, and lower cellular circularity compared to those in 4 wt% and 6 wt% CA scaffolds, suggesting a more prominent presence of cell clusters in softer substrates compared to stiffer substrates. The results also showed cells in 6 wt% CA having a higher average cell migration speed compared to those in 2 wt% and 4 wt% CA scaffolds, indicating a positive relationship between substrate stiffness and cell migration velocity. Findings from this experiment may contribute to the development of enhanced in vitro 3D breast tumor models for basic cancer research using 3D porous biomaterial scaffolds.
Show less - Date Issued
- 2019
- Identifier
- CFH2000492, ucf:45626
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFH2000492
- Title
- Influence of Chitosan-Alginate Scaffold Stiffness on Bone Marrow Stromal Cell Differentiation.
- Creator
-
Arias Ponce, Isabel, Florczyk, Stephen, Fang, Jiyu, Khaled, Annette, Leon, Lorraine, University of Central Florida
- Abstract / Description
-
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
- Title
- Fabrication and Investigation of an enzyme-free, Nanoparticle-based Biosensor for Hydrogen Peroxide determination.
- Creator
-
Neal, Craig, Seal, Sudipta, Cho, Hyoung Jin, Florczyk, Stephen, University of Central Florida
- Abstract / Description
-
Electrochemical biosensors often employ enzymes as detection elements. These sensors are highly selective towards target analytes, however the scope of their application is limited by the poor stability of the enzyme. In this study, multi-valent inorganic cerium oxide nanoparticles were used as detection elements for the analysis of hydrogen peroxide. The electrochemical response of the cerium oxide towards hydrogen peroxide analyte is defined through cyclic voltammetry and chronoamperometry....
Show moreElectrochemical biosensors often employ enzymes as detection elements. These sensors are highly selective towards target analytes, however the scope of their application is limited by the poor stability of the enzyme. In this study, multi-valent inorganic cerium oxide nanoparticles were used as detection elements for the analysis of hydrogen peroxide. The electrochemical response of the cerium oxide towards hydrogen peroxide analyte is defined through cyclic voltammetry and chronoamperometry. This response was found to be dependent on nanoparticle Ce3+:Ce4+ redox state ratio and this property is exploited to fabricate a biosensor. As produced, the biosensor demonstrated sensitivity at picomolar analyte concentrations. Further, the sensitivity of the electrode is stable across a range of temperatures and pH's which inhibit the function of standard enzyme-based sensors. Additionally, the produced sensor retained function in sheep serum demonstrating the high selectivity and robustness of the sensor.
Show less - Date Issued
- 2016
- Identifier
- CFE0006362, ucf:51540
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006362
- Title
- The Formation and Characterization of Mesoscopic J- and H-aggregates with Controlled Morphologies by the Co- and Templated Assembly of Cyanine Dyes.
- Creator
-
Rhodes, Samuel, Fang, Jiyu, Jiang, Tengfei, Dong, Yajie, Florczyk, Stephen, Pang, Sean, University of Central Florida
- Abstract / Description
-
The supramolecular aggregates of ?-conjugated molecules have become an area of great interest to the scientific community in recent years for their promise in biosensors and optoelectronic devices. Among various supramolecular aggregates, J- and H-aggregates of ?-conjugated dye molecules are particularly interesting because of their unique optical and excitonic properties that are not given by individual molecules. H-aggregates are composed of dye molecules in a face-to-face stacking, giving...
Show moreThe supramolecular aggregates of ?-conjugated molecules have become an area of great interest to the scientific community in recent years for their promise in biosensors and optoelectronic devices. Among various supramolecular aggregates, J- and H-aggregates of ?-conjugated dye molecules are particularly interesting because of their unique optical and excitonic properties that are not given by individual molecules. H-aggregates are composed of dye molecules in a face-to-face stacking, giving rise to a blue-shifted absorption band compared with the monomer band and a strong emission quenching. In contrast, J-aggregates represent an edge-to-edge stacking of dye molecules, showing a red-shifted absorption band with respect to the monomer band and a strong fluorescence emission. However, the use of J- and H-aggregates in biosensors and optoelectronic devices remains a challenge because of the difficulty of controlling their sizes and morphologies. In this dissertation, we develop two different paths for controlling the size and morphology of J- and H-aggregates. First, we show that the co-assembly of cyanine dyes and lithocholic acid (LCA) in ammonia solution can lead to the formation of mesoscopic J- and H-aggregate fibers, depending on the condition under which the co-assembly occurs. Second, we report the formation of mesoscopic J-aggregate tubes by using the preformed LCA tubes as a template. The structure, optical, and electronic properties of these J- and H-aggregate fiber and tubes are studied as a function of temperature. Finally, we exploit their applications as photo-induced electron transfer supramolecular probes for the detection of dopamine, an important neurotransmitter in central and peripheral nervous systems.
Show less - Date Issued
- 2018
- Identifier
- CFE0007412, ucf:52718
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007412
- Title
- Regolith-Based Construction Materials for Lunar and Martian Colonies.
- Creator
-
Grossman, Kevin, Seal, Sudipta, Florczyk, Stephen, Fang, Jiyu, Zhai, Lei, Leuenberger, Michael, University of Central Florida
- Abstract / Description
-
Humankind's ambitions of exploring our solar system and parts beyond depend heavily on our ability to collect resources from local environments at our destinations rather than bringing materials on the journey. This is a concept known as in-situ resource utilization (ISRU) and it is one that has been understood by every explorer and settler in the history of humankind. Regolith on the moon and Mars has been shown to be a particularly useful resource and has the ability to provide humans with...
Show moreHumankind's ambitions of exploring our solar system and parts beyond depend heavily on our ability to collect resources from local environments at our destinations rather than bringing materials on the journey. This is a concept known as in-situ resource utilization (ISRU) and it is one that has been understood by every explorer and settler in the history of humankind. Regolith on the moon and Mars has been shown to be a particularly useful resource and has the ability to provide humans with resources including water, oxygen, construction material, fabric, radiation shielding, metals, and may more. This dissertation focuses on construction materials derived from standard regolith simulant JSC-1A, including bricks, composites, metals and modified powder materials. Sintering processes with JSC-1A were studied to determine optimal heating profiles and resulting compressive strengths. It was determined that the temperature profiles have an optimal effect on smaller particle sizes due to the larger surface area to volume ratio of small particles and sintering being a surface event. Compressive strengths of sintered regolith samples were found to be as high as 38,000 psi, which offers large utility for martian or lunar colonies. This study also investigates a method for extracting metals from regolith known as molten regolith electrolysis. The alloy of the two major metallic components of regolith, iron and silicon, has been investigated as a structural metal for colonies and a potential feedstock for novel metallic 3D printers. Parallel to these efforts, a new additive manufacturing technique designed to print metal parts in low and zero gravity environments is developed. The mechanical properties from metal parts from this technique are examined and it is determined how the printing process determines a microstructure within the steel that impacts the utility of the technology.
Show less - Date Issued
- 2018
- Identifier
- CFE0007331, ucf:52144
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007331
- Title
- Assessment of Microstructure and Mechanical Behavior of Materials and Phases Observed in Low-Enriched Uranium Monolithic Fuel Plates After Fabrication.
- Creator
-
Newell, Ryan, Sohn, Yongho, Florczyk, Stephen, Fang, Jiyu, Keiser, Dennis, Kwok, Kawai, University of Central Florida
- Abstract / Description
-
Low enriched uranium (LEU) fuels are being developed to reduce the use of highly enriched uranium in power generation to reduce proliferation risks. Challenges arise in providing sufficient fissile U in LEU without reactor redesign. As such, a novel monolithic fuel plate design employs LEU alloyed with 10 wt. % Mo. Throughout fabrication of these fuel plates, metallurgical transformations and reactions take place as a result of elevated temperatures during processing. The transformations...
Show moreLow enriched uranium (LEU) fuels are being developed to reduce the use of highly enriched uranium in power generation to reduce proliferation risks. Challenges arise in providing sufficient fissile U in LEU without reactor redesign. As such, a novel monolithic fuel plate design employs LEU alloyed with 10 wt. % Mo. Throughout fabrication of these fuel plates, metallurgical transformations and reactions take place as a result of elevated temperatures during processing. The transformations include decomposition of the metastable body-centered cubic ? phase in the fuel and metallurgical interactions at interfaces between fuel plate components. This work aims to provide further understanding into physical and mechanical behavior of these constituents as they relate to fuel plate processing and performance. Fuel plate processing includes alloying the U, applying a Zr diffusion barrier, and cladding in AA6061 via hot isostatic press. Experimental Zr barriers were applied via electroplating, plasma-spraying, or roll-bonding and characterized using optical and electron microscopy, demonstrating that roll-bonded Zr exhibits the most favorable properties. During fabrication, regions of the ?-U decompose into ? and ?' which revert to ? during annealing or irradiation and heat treatments were designed to induce similar transformations and characterize them using x-ray diffraction and electron microscopy, resulting in a model describing the reversion as a function of time and temperature. The mechanical properties of the fuel and other constituent phases were investigated via instrumented indentation of fuel plates. Phases that occurred in small, discontinuous regions were fabricated in diffusion couples for more reliable indentation. The kinetic and mechanical data produced from this study can be used to estimate the phase constitution of the fuel plates and subsequently, its behavior in response to fabrication and irradiation.
Show less - Date Issued
- 2018
- Identifier
- CFE0007349, ucf:52109
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007349
- Title
- Development of in vitro point of care diagnostics (IVPCD) based on Aptamers integrated Biosensors.(&)nbsp;.
- Creator
-
Saraf, Nileshi, Seal, Sudipta, Fang, Jiyu, Florczyk, Stephen, Dong, Yajie, Self, William, University of Central Florida
- Abstract / Description
-
The global market for the medical diagnostic industry is worth 25 billion dollars in the United States and is expected to grow exponentially each year. Presently available methods for biodetection, such as immunoassays, chemiluminescence and fluorescent based assays are expensive, time consuming and require skilled labor with high-end instruments. Therefore, development of novel, passive colorimetric sensors and diagnostic technologies for detection and surveillance is of utmost importance...
Show moreThe global market for the medical diagnostic industry is worth 25 billion dollars in the United States and is expected to grow exponentially each year. Presently available methods for biodetection, such as immunoassays, chemiluminescence and fluorescent based assays are expensive, time consuming and require skilled labor with high-end instruments. Therefore, development of novel, passive colorimetric sensors and diagnostic technologies for detection and surveillance is of utmost importance especially in resource constrained communities. The present work focusses on developing novel and advanced in vitro biodiagnostic tools based on aptamer integrated biosensors for an early detection of specific viral proteins or small biomolecules used as potential markers for deadly diseases. Aptamers are short single stranded deoxyribonucleic acid (DNA) which are designed to bind to a specific target biomolecule. These are readily synthesized in laboratory and offers several advantages over antibodies/enzymes such as stable in harsh environment, easily functionalized for immobilization, reproducibility etc. These undergo conformational changes upon target binding and produces physical or chemical changes in the system which are measured as colorimetric or electrochemical signals. Here, we have explored the aptamer-analyte interaction on different platforms such as microfluidic channel, paper based substrate as well as organic electrochemical transistor to develop multiple compact, robust and self-contained diagnostic tools. These testing tools exhibit high sensitivity (detection limit in picomolar) and selectivity against the target molecule, require no sophisticated instruments or skilled labor to implement and execute, leading a way to cheaper and more consumer driver health care. These innovative platforms provide flexibility to incorporate additional or alternative targets by simply designing aptamers to bind to the specific biomolecule.
Show less - Date Issued
- 2018
- Identifier
- CFE0007766, ucf:52388
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007766
- Title
- Simultaneous Measurement of Isotope-free Tracer and Interdiffusion Coefficients in Sandwich Type Diffusion Couples.
- Creator
-
Schulz, Esin, Sohn, Yongho, Bai, Yuanli, Florczyk, Stephen, Coffey, Kevin, Orlovskaya, Nina, University of Central Florida
- Abstract / Description
-
The experimental determination of the tracer or self-diffusion coef?cient as a function of composition can be quite burdensome in alloys since separate measurements must be carried out for each alloy composition. A new formalism recently developed by I.V. Belova, N.S. Kulkarni, Y.H. Sohn and G.E. Murch, based on linear response theory combined with the Boltzmann(-)Matano method allows determination of tracer and interdiffusion coef?cients simultaneously from a single, isotope-free solid to...
Show moreThe experimental determination of the tracer or self-diffusion coef?cient as a function of composition can be quite burdensome in alloys since separate measurements must be carried out for each alloy composition. A new formalism recently developed by I.V. Belova, N.S. Kulkarni, Y.H. Sohn and G.E. Murch, based on linear response theory combined with the Boltzmann(-)Matano method allows determination of tracer and interdiffusion coef?cients simultaneously from a single, isotope-free solid to solid diffusion couple experiment. In this study, for the first time, an experimental investigation with an analytical approach based on the new formalism has been carried out in the binary Cu-Ni system. Pure Cu and Ni thin films were deposited in between several binary diffusion couples with varying terminal alloy compositions (such as Cu, Cu-25Ni, Cu-50Ni, Cu-75Ni, Ni). Diffusion couples were then annealed at 800(&)deg;C, 900(&)deg;C and 1000(&)deg;C. After annealing, the couples were water quenched, cross-sectioned, and prepared for compositional characterization. Scanning Electron Microscopy was employed to examine the interdiffusion zone. Energy Dispersive X-ray Spectroscopy was conducted to obtain concentration profiles for quantitative analysis. The superposition of the concentration profiles of thin film and interdiffusion were analyzed for the simultaneous determination of tracer and interdiffusion coefficients. The tracer diffusion coefficient of Cu, tracer diffusion coefficient of Ni and inter-diffusion coefficients simultaneously determined using the experimental methodology based on the novel formalism derived, and produced results consistent with previously reported values determined independently by radiotracer and interdiffusion experiments.
Show less - Date Issued
- 2018
- Identifier
- CFE0007368, ucf:52101
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007368
