Bone is currently the second most transplanted tissue, second only to blood. However, significant hurdles including graft supply and implant failure continue to plague researchers and clinicians. Currently, standard clinical procedures include autologous and allogeneic grafting. Autologous grafts may achieve functional repair; yet, they are available in limited supply and are associated with donor site morbidity. Allogeneic grafts are available in greater supply, but have a higher risk of infection. To overcome the disadvantages of current grafts, tissue engineering has become a major focus for the regeneration of bone. The goal of tissue engineering is to use a multidisciplinary approach to create biomimetic constructs that stimulate osteogenic regeneration to heal bone defects and restore tissue function. Biodegradable scaffolds are used in tissue engineering strategies as an interim template for tissue regeneration. The scaffold architecture provides mechanical support for cell attachment and tissue regeneration. Biocompatible poly(lactic-co-glycolic acid) (PLGA) has been processed through a number of techniques to create porous 3D architectures. Hydroxyapatite (HAP) and tricalcium phosphate have been used in conjunction with polymer scaffolds due to their osteoconductivity and biocompatibility, but they often lack osteoinductivity and are resistant to biodegradation. Conversely, amorphous calcium phosphate (ACP) is a mineral that solubilizes under aqueous conditions, releasing calcium and phosphate ions, which have been postulated to enhance osteoblast differentiation and mineralization. Controlled dissolution can be achieved by stabilizing ACP with divalent cations such as zinc or copper. Furthermore, incorporation of such osteogenic ACPs within a biodegradable PLGA scaffold could enhance the osteoconductivity of the scaffold while providing calcium and phosphate ions to differentiating osteoprogenitor cells, thereby stimulating osteogenesis when implanted in vivo. In this research, the effect of zinc on the differentiation of osteoprogenitor cells was investigated. Zinc supplementation of the culture media had no stimulatory effect on cell proliferation or differentiation. ACPs were synthesized using zirconium (ZrACP) and zinc (ZnACP) as stabilizers to achieve sustained ion release. Elevated concentrations suggested sustained ion release over the course of 96 hours and enhanced solubility of ZrACP and ZnACP. X-ray diffraction analysis showed a conversion of ZrACP to a semi-crystalline material after 96 hours, but ZnACP showed no conversion after 96 hours. Composite scaffolds were fabricated by incorporating HAP, zirconium-stabilized ACP (ZrACP), or zinc-stabilized ACP (ZnACP) into a sintered PLGA microsphere matrix and then characterized to determine the effect of the minerals on the in vitro differentiation of MC3T3-E1 cells. Scanning electron microscopy revealed a porous microsphere matrix with calcium phosphate powders distributed on the surface of the microspheres. Measurements of mechanical properties indicated that incorporation of 0.5 wt% calcium phosphates resulted in a 30% decrease in compressive modulus. When cells were cultured in the scaffolds, composite ACP scaffolds stimulated proliferation and ALP activity, while HAP scaffolds stimulated osteoblast gene expression. Overall, the results of this work indicate the addition of calcium phosphate minerals to PLGA scaffolds supported cell growth and stimulated osteogenic differentiation, making the scaffolds a promising alternative for bone tissue regeneration. / Ph. D.

This dissertation is comprised of three independent but interconnected studies with the scope of further understanding uranium and iodine partitioning between apatite and fluid. The studies herein presented investigated: 1) brushite to apatite crystallization method; 2) the degree of uranium incorporation into apatite; 3) the degree of iodine incorporation into apatite. The importance of this work is assessing the role of apatite in immobilizing these elements, where uranium is a major component of spent nuclear fuel and iodine is a chemical analog of its radioactive isotope (129I). Once we understand the incorporation mechanisms, we will provide data that can be used in development of engineering barrier systems via add-on of phosphate minerals. In the first chapter we evaluate a method for the crystallization of apatite (Ca10(PO4)6(OH, F, Cl)2) using brushite (CaHPO4·2H2O) as initial material. The solutions evaluated for this transformation were NaCl, NaF, and KOH. Result yielded 100% apatite transformation from brushite when pH is 3.5 or greater. At a pH lower than 3.5, transformation yields monetite-apatite mixtures. Crystal size is reduced during the transformation from ~10 micrometer to ~1 micrometer. In the second chapter, degree of uranium uptake by apatite was evaluated. Phosphate minerals were crystallized from U-bearing NaCl solutions at 25-350°C. After experimental runs uranium concentrations in experimental solids and fluids were analyzed using Inductively Coupled Plasma – Mass Spectrometry. Additionally, characterization of the solids was performed via X-Ray Diffraction, Scanning Electron Microscopy and Electron Microprobe to confirm the brushite to apatite conversion. Results show that >90% of uranium was extracted from solution. Moreover, that the partitioning of uranium between apatite and fluid decreases with increasing temperature. In the third chapter apatite was crystallized from iodine-bearing solutions. The crystallization was evaluated at 39 and 200°C. Iodine concentration in solids were acquired via Electron Microprobe Analysis (EMPA) whereas iodine concentration in fluids were acquired via UV-Visible Spectrophotometry. Iodine concentrations in fluids yielded minimum depletion (0.1M) from initial iodine added to the system (0.1M). Partitioning data suggest that iodate (the oxidized form of iodine) is more compatible with apatite compared to iodide (the reduced state of iodine).

No description available.

京都大学 / 新制・課程博士 / 博士(医学) / 甲第24836号 / 医博第5004号 / 新制||医||1068(附属図書館) / 京都大学大学院医学研究科医学専攻 / (主査)教授 安達, 泰治, 教授 森本, 尚樹, 教授 上杉, 志成 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

Phosphorus is needed by living organism including humans and plants, to survive. Imbalance in phosphate concentration in human body can result in numerous diseases or disorders while excess phosphorus levels in water bodies like lakes, and rivers, are responsible for the rise in incidence of algal bloom across world. Current commercial phosphate monitoring systems are dominated by colorimetric measurements while electrochemical sensors including potentiometric, amperometric and voltammetric sensors are still in the research phase. Electrochemical sensors require stable reference electrodes for reliable measurements that pose challenges for miniaturization. Solid state potentiometric sensors are widely explored due to their rapid response, easy fabrication and simple electronic measurement system. However, the sensor miniaturization is dependent both on the working and reference electrode. Metal electrodes like cobalt offers advantages such as reagent-free detection, easy to miniaturize but the sensitivity of zero-current potentiometric sensors is limited by the theoretical Nernstian limit and cobalt sensors also require chemical pretreatment in standard solution before measurement. Here, an in situ electrical pretreatment method is proposed to eliminate the need of chemical pretreatment and enhance the sensitivity of cobalt electrodes to -91.4 mV/ decade of phosphate concentration. However, this electrode still needs a reference electrode for reliable measurements. Therefore, this study has demonstrated a chemiresistive sensing platform for solid state detection of phosphate using both enzyme and enzyme-free methods. A rapid prototyping method was developed to pattern the thin metal films (~100 nm thickness) using a bench top plotter cutter. The method was used to fabricate thin gold film contact electrodes for chemiresistors. The thin gold leaf contact electrodes exhibited low-noise and offered a robust, rapid and reproducible manufacturing process for chemiresistors. The chemiresistive sensor showed a wide measuring range (0.5 ppm to 500 ppm) for hydrogen peroxide detection. The sensor was deposited with glucose oxidase to demonstrate the application of the sensor for peroxidase assays to detect glucose in standard buffer solution and human pooled plasma. Phosphate also is detected using pyruvate oxidase in presence of pyruvate to generate hydrogen peroxide as the detectable molecule. Finally, metal phthalocyanines were used to perform enzyme-free phosphate measurements. This work demonstrated the sensor technologies which could be used for in-field phosphate monitoring to prevent algal bloom and it also provides phosphate monitoring methods for rapid detection in medical diagnostics for early diagnosis for diseases like chronic kidney disease and to improve the patient’s outcomes for such diseases. / Thesis / Doctor of Philosophy (PhD) / Phosphorus is an essential element for the survival of living beings including humans and plants because it is needed in multiple physiological pathways and functions like cellular signalling, energy storage, metabolism and maintenance. Therefore, phosphate in the human body is strictly regulated and in disease conditions like chronic kidney disease, and metabolic disorders. It can increase or decrease resulting in ailments and worsening of diseases. Phosphorus is also extensively used in the agricultural field to improve the growth and crop yield. Excess phosphorus from these fertilizers can enter our water sources via agricultural water run-offs leading to the increasing incidences of algal bloom across world. Current phosphorus measuring systems require chemicals which generates toxic waste, needs manual sample collection and transport, and have narrow measuring ranges. There is an urgent need for sensors which would eliminate the need of sample collection and processing, do not require toxic chemicals and could work over a wide detection range. This study presents two solid-state sensor technologies which would simplify the phosphate detection for both environmental and medical diagnostics samples.

Heavy metals, oxyanions (NO3-, PO4-), pharmaceuticals, and dyes in aquatic environments are inevitable economic and health concerns. Ingestion of these contaminants, even in trace amounts, causes long and short-term serious threats to human health. Conventional pollutant mitigation strategies can be costly or ineffective. Due to high efficiency, simplicity, low price, adsorbent reuse, and pollutant (e.g., phosphates) recovery, adsorption has been widely used for wastewater purification. Many efficient, environmentally compatible, and cost-effective sorbents have been successfully applied in environmental remediation. Chapter I is about characterization of graphene-coated pinewood biochar hybrids and evaluation of their copper removal performances. Here, we synthesized three types of pinewood biochar-graphene composites consisting of three different graphene precursors and compared their aqueous Cu2+ removal performances against raw pinewood biochar. To the best of our knowledge, no previous work has characterized the copper decontamination by graphene-biochar hybrids. Chapter II is about thermally- and chemically-treated lignite adsorbents for phosphate remediation. We engineered a cost efficient lignite system with co-precipitated Ca2+/Mg2+ followed by pyrolysis at 600 ⁰C to remediate aqueous phosphates. Micro-sized surface deposited oxide/hydroxide/carbonate particles promoted phosphate uptake of Ca2+/Mg2+-modified-lignite by 31 and 72 times, compared to thermally treated lignite (w/o a chemical treatment) and the raw lignite, respectively. The exhausted adsorbent can act as a slow-release fertilizer, which is comparable with commercial phosphate fertilizers. Chapter III is about synthesis of activated lignite [A-L], Ca2+-modified lignite [Ca-L], and Fe3O4 nanoparticle-loaded activated lignite (Fe3O4-A-L) for phosphate remediation. Even though A-L has a very high surface area (2854 m2/g), it did not achieve much phosphate sorption. Ca-L phosphate uptake was highest due to the high concentrations of surface deposited CaCO3, CaO, and Ca(OH)2. A pH-independent (from pH 5 to 9) phosphate removal was reported by highly basic Ca-L. However, the Ca2+ leaching was highest at pH 5. Precipitation of Ca2+ phosphates/hydrophosphates is the major phosphate removal mechanism of Ca-L. Fe3O4 and Fe2O3 sites of Fe3O4-A-L enhanced phosphate adsorption capacity, 8-fold versus A-L (67.6 mg/g vs 8.0 mg/g at 25 ºC). Fe3O4-A-L remediated phosphates via inner-sphere surface complexation and precipitation.

Eutrophication, caused by phosphate, can be detrimental both for the aquatic environment and human health. This research aims to provide deep knowledge about the adsorption properties of low-cost Fe/Mg layered double hydroxide modified biochar (LDHBC) for removal of phosphate from aqueous solution. Firstly, Fe/Mg layered double hydroxide (LDH) was synthesized by mixing FeCl3 and MgCl2. 6H2O salts in water, followed by NaOH treatment (coprecipitation method). For LDHBC, FeCl3, and MgCl2. 6H2O salts were dissolved in water, and Douglas fir biochar was added to the salts mixture to make a slurry, followed by NaOH treatment. The surface chemistry and elemental composition of both adsorbents and phosphate-laden adsorbents were characterized using Elemental analysis, BET, PZC, TGA, DSC, XRD, SEM, and TEM. Adsorption ability of LDH and LDHBC was studied by pH effects, kinetics, and the highest capacity for the analyte.

The thesis investigates pipeline plugging mechanisms that have occurred during interim stabilization transfers at Hanford. A laboratory-scale saltwell pumping test loop was designed to evaluate a surrogate of Hanford Tank 241-SX-104 supernate. The effect of surrogate flow rate, cooling water flow rate and phosphate concentrations on plugging mechanisms was investigated. Critical parameters like particle and agglomerate size, velocity and bed growth rate were determined. Theoretical models were used to compare the experimental pressure rise and temperature drop of the surrogate in the channel. An operating region in which a plug would not form was developed, based on the experimental results. Experiments are also reported on plug remediation. Unplugging experiments at varying pump pressure heads and residence time of plug in the line were performed.

No description available.

No description available.