Dissertations / Theses on the topic 'Calcium-deficient'

Thesis (Honors)--Ohio State University, 2007.
Title from first page of PDF file. Document formatted into pages: contains 11 p.; also includes graphics. Includes bibliographical references (p. 10-11). Available online via Ohio State University's Knowledge Bank.

ATP-sensitive potassium (KATP) channels link membrane excitability to metabolism. They are regulated by intracellular nucleotides and other factors, and have been shown to play a role in development of skeletal muscle force, but controversy surrounds their role during fatigue. The aim of this research project was to determine the role of KATP channel under conditions that allow for better assessment of changes in force during fatigue, by virtue of using a smaller whole muscle model less subject to anoxia. Thus, the first objective was to determine the effect of the loss of KATP channel activity on force during fatigue in small FDB muscle bundles. KATP channel deficient fibers had faster and greater decreases in peak tetanic force during fatigue, developed greater resting tension, and had lower force recovery following fatigue compared to control wild type muscles. The second objective was to determine whether the functional impairment in skeletal muscle without KATP channel activity was due to an increase in Ca 2+ influx. When [Ca2+]e was reduced or L-type Ca2+ channels partially blocked, Kir6.2-/- FDB muscle had slower fatigue development, less resting tension, and had an improved force recovery. A novel phenomenon was observed while studying the effect of KATP channel activity in vitro. During a second bout of fatigue the decrease in peak tension was significantly lower than the decrease during the first bout of fatigue. Furthermore, the deleterious effects of the loss of KATP channel activity during an initial fatigue were absent during the second fatigue in FDB exposed to glibenclamide. It is concluded (i) that the KATP channel is important to prevent impairment of function during fatigue, (ii) that this impairment of function is due to an increase in Ca2+ influx through L-type Ca2+ channels, causing Ca2+ overload, and (iii) that fatigue resistance increases while the dependency on the KATP channel to prevent function impairment and fiber damage decreases following one fatigue bout at 37°C; a phenomenon here termed fatigue pre-conditioning.

Nutrients and cations have significant effect on activated sludge characteristics and therefore effect the efficiency of whole processes. To determine the properties in phosphorus deficient medium and the effect of calcium ions two reactor sets with two different phosphorus concentration (C/N/P=100/5/0.05 and C/N/P=100/5/1), three different concentrations of calcium (0.5, 5, 15 meq/L) were operated with 8 days of sludge residence time and an effective volume of 2 L. Results showed amount and composition of EPS was dependent on calcium and phosphorus concentrations. Except for the highest calcium concentration, increase in phosphorus concentration resulted in increase in total EPS production. Under phosphorus deficient conditions, calcium ions stimulated the production of carbohydrate type polymers and viscous bulking was observed. However, the increase in phosphorus concentration led to increase in protein type polymer production and bulking condition was cured. Addition of calcium ions increased conductivity in both cases, but increase in phosphorus concentration caused decrease in conductivity. Increase in phosphorus concentration had improved settleability, dewaterability and rheology of sludge. Moreover, effluent turbidity was decreased and COD removal efficiency was recorded as greater than 95 % for all calcium concentrations under phosphorus sufficient conditions. Microscopic analyses showed that under phosphorus deficient conditions flocs were weak, dispersed and nonresistant. Increase in phosphorus concentration resulted in improvement of floc structure. Same Enterobacter and Citrobacter species were identified at all calcium concentrations under phosphorus deficient conditions. Yet, under phosphorus sufficient conditions different species were identified in control reactor as compared to 5 meq/L and 15 meq/L concentrations.

The effects of dietary calcium and phosphorus levels on audiogenic seizure susceptibility and brain neurotransmitter were investigated in magnesium deficient rats. For 17 days, male weanling rats were fed magnesium deficient diets which also contained deficient (-), adequate (=}, and excess (+) amounts of calcium and/or phosphorus. Reduction of seizure incidence was seen in low calcium and/or low phosphorus diets. High calcium, and high calcium in combination with high phosphorus increased the severity of seizures. High calcium and low phosphorus, and high phosphorus and low calcium diets prevented seizuring. Most magnesium deficient diets resulted in elevation of serum phosphorus, calcium, and sodium concentrations. Within diet treatments, animals that seized had higher serum mineral concentrations than animals that failed to seize. Magnesium deficiency increased serotonin in cerebral cortex, cerebellum, and medulla oblongata and pons, and 5-hydroxyindoleacetic acid concentrations in cerebral cortex. There were no significant diet effects in brain neurotransmitter concentrations in the midbrain. Calcium seemed to play an important role in increasing both audiogenic seizure susceptibility and brain neurotransmitters. However, brain neurotransmitter levels were not related to seizure susceptibility. Calcium increased serum potassium and sodium concentrations and it increased brain serotonin concentration overall. Increasing dietary phosphorus levels increased serum phosphorus decreased serum calcium concentrations, but did not affect brain neurotransmitters.

Ce travail a consisté à élaborer un biomatériau hybride constitué d’un tissu de fibres de carbone (TFC) revêtu de phosphates de calcium (CaP) déposés par un procédé de sono-électrodéposition et à étudier l’influence des paramètres expérimentaux sur la composition chimique, la microtexture et la structure des revêtements phosphocalciques, ainsi que la biocompatibilité in vitro du biomatériau hybride. La densité de courant s’est avérée être un paramètre important. Pour de fortes densités de courant (≥ 100 mA/g), un régime d’électrolyse rapide de l’eau entraîne la formation d’un dépôt aciculaire d’hydroxyapatite déficitaire en calcium (CaD-HAP) carbonatée avec la présence éventuelle d’une phase de calcite. Pour de faibles densités de courant (≤ 50 mA/g), un régime d’électrolyse lent de l’eau entraîne la formation d’un dépôt plaquettaire de CaD-HAP carbonatée issu de l’hydrolyse in situ du phosphate octocalcique plaquettaire préalablement précipité. Pour l’ensemble des dépôts, les particules sont constituées d’un coeur de CaD-HAP carbonatée de structure ordonnée et d’une surface hydratée de CaD-HAP carbonatée de structure désordonnée qui résulte de l’existence d’une zone de sursaturation lors de la précipitation des CaP. La sono-électrodéposition se révèle être un procédé versatile capable d’orienter la synthèse des phases de CaP, avec pour une faible densité de courant appliquée l’obtention d’un dépôt biomimétique comparable à la partie minérale du tissu osseux obtenue par le processus d’ostéogénèse naturelle. Des tests de viabilité in vitro réalisés avec des ostéoblastes humains primaires ont montré que la nanoporosité et le caractère hydrophile des TFC n’impactent pas la biocompatibilité et que les paramètres tels que le précurseur des fibres, l’ensimage et/ou la forme lobée des fibres semblent favoriser l’adhésion et la prolifération des cellules
This work is focused on the synthesis of a novel hybrid biomaterial made of carbon fibers cloth (CFC)/ calcium phosphates (CaP) using the sono-electrochemical technique and the study of the influence of experimental parameters on the chemical composition, microtexture and structure of CaP deposits and on in vitro biocompatibility. Current density is shown to be a crucial parameter. Specifically, at high current densities ((≥ 100 mA/g), the fast water electrolysis rate leads to a needle-like deposit consisting in a major phase of carbonated calcium deficient hydroxyapatite (CaD-HAP) mixed with a calcium carbonate phase. At low current densities (≤ 50 mA/g), the slow water electrolysis rate generates a plate-like carbonated CaD-HAP phase, coming from the in situ hydrolysis of a former octacalcium phosphate phase. Whatever the experimental conditions, particles of the deposits consists in a carbonated CaD-HAP core showing an ordered structure, surrounded by a hydrated and disordered carbonated CaD-HAP surface layer which results of the formation of oversaturated domains during CaP precipitation. Sono-electrodeposition is shown to be a versatile process able to control the nature of CaP phases. Especially, at low current density a biomimetic CaP deposit is obtained, similar to the mineral part of bones produced during natural osteogenesis. In vitro biologic tests using primary human osteoblasts showed that the nano-porosity and hydrophilicity of the carbon fibers do not affect the biocompatibility and that fiber precursor, sizing and lobe shaped fibers seems to favor adhesion and proliferation of human cells

The structural properties of the very neutron deficient systems around N~Z~40 have been studied in two experiments performed at the GANIL and Legnaro laboratories. The fragmentation of a 60 MeV/u92 Mo beam on a natural nickel target at the GANIL Laboratory, France, produced exotic nuclei along the proton drip line in the mass 80 region. Isomeric decays have been observed for the first time in the N=Z+2 systems 74 36Kr, 80 39Y and 84 41Nb. The isomer in 74 Kr is interpreted as the hindered decay from an excited 0+ state, supporting the long-standing prediction of prolate/oblate shape coexistence in this nucleus. Transitions from states below an isomer in the N=Z nucleus 86 43Tc have also been tentatively identified, making this the heaviest N=Z system for which gamma-ray decays from excited states have been observed. Conclusive evidence for the existence of the Z=N+1 isotopes 77 39Y, 79 40Zr and 83 42Mo has also been obtained together with upper limits on the particle decay lifetimes of the odd-proton systems 81 41 Nb and 85 43Tc. The reported instability of the lighter odd-Z, Tz = -1/2 systems 69Br and 73Rb makes the observed existence for 77 39Y particularly interesting. A possible explanation for the relative particle stability of 77 39Y is given in terms of the shape polarising effect of the N=Z=38 prolate shell gap on the nuclear mean field and the increased centrifugal barrier associated with the occupation of a g9/2 proton orbital. The second experiment was performed to further investigate the oblate nature of the isomeric state in 74Kr. The reaction 40Ca(40Ca, alpha2p)74Kr was used at a beam energy of 135 MeV obtained from the Tandem XTU accelerator. The EUROBALL gamma-ray array was used in conjunction with the ISIS charged particle silicon ball to study the states above and below the isomer. The ISIS ball was used to highlight channel selection of non-yrast states by particle gating. No evidence for the 0+2 isomer in 74Kr was observed in this work.

Este trabalho visou a produção de suportes para crescimento celular constituídos de compósitos de poli(L-lactídeo) (PLLA) e diversos tipos de fosfatos de cálcio (CaP). A hidroxiapatita deficiente em cálcio (HAD) e o fosfato octacálcico (OCP) em tamanhos submicrométricos foram sintetizados. Hidroxiapatita (HA) e o β-fosfato tricálcico (β-TCP) foram adquiridos da Sigma-Aldrich. Uma mistura de HAD:β-TCP (7:3) também foi preparada. Para melhorar a dispersão da fase mineral em uma matriz polimérica de PLLA, utilizou-se cloreto de lauroíla para funcionalizar a superfície dos CaP. Os espectros de infravermelho e a análise termogravimétrica confirmaram a presença de laurato na superfície de partículas de CaP. As partículas de HA pura também foram funcionalizadas com cloreto de lauroíla para fins comparativos. Compósitos de PLLA/CaP-laurato foram fabricados utilizando a técnica de eletrofiação. A funcionalização da superfície do CaP com laurato resultou em uma melhoria significativa na dispersão de partículas de CaP na matriz polimérica, permitindo a inclusão de até 40% da fase mineral sem comprometer as propriedades mecânicas. Microscopia eletrônica de varredura (SEM) e microscopia eletrônica de transmissão (TEM) foram utilizadas para investigar a morfologia da fibra. A perda de massa e a liberação de cálcio dos suportes durante a degradação em uma solução salina tamponada com fosfato (PBS) foram medidas. HAD e OCP se mostraram ser mais solúveis do que HA e HAD:β-TCP (7:3). A bioatividade dos compósitos foi investigada por imersão das fibras em um fluido corporal simulado (SBF) a 37 °C e pH 7.4. Embora todos os suportes de PLLA/CaP-laurato foram capazes de formar uma camada de apatita em sua superfície após a exposição em SBF, os resultados demonstraram um aumento significativo na mineralização quando HAD, OCP e HAD:β-TCP (7:3) são a fase mineral no compósito em vez da HA. Além disso, malhas produzidas a partir das fibras eletrofiadas de PLLA/CaP-laurato, utilizadas como suporte para crescimento celular, favoreceram a adesão e proliferação de células de fibroblastos de camundongo (NIH-3T3) e células tronco mesenquimais de dentes decíduos humanos (SHED). Finalmente, suportes a partir das malhas PLLA/HAD-laurato e PLLA/OCP-laurato apresentaram melhor desempenho para acelerar a calcificação in vitro como resultado da osteoindução de células SHED e de células pré-osteoblásticas derivadas de calvária de rato (MC3T3-E1) se comparados aqueles contendo HA e HAD:β-TCP (7:3). Esses novos materiais são propostos como biocompósitos de rápida degradação de CaP, para serem utilizados em aplicações de regeneração óssea em ortodontia e ortopedia.
This work aimed at the generation of scaffolds for cellular growth constituted by poly(L-lactide) (PLLA) and several types of calcium phosphate (CaP). Calcium deficient hydroxyapatite (HAD) and octacalcium phosphate (OCP) were synthesized in submicrometer sizes. Hydroxyapatite (HA) and β-tricalcium phosphate (β-TCP) were purchased from Sigma-Aldrich. A mixture of HAD:β-TCP (7:3) also was prepared. In order to improve the dispersion of the mineral phase in a PLLA polymeric matrix, lauroyl chloride was used to functionalize the surface of CaP. Infrared spectra and thermal gravimetric analysis confirmed the presence of laurate on the surface of CaP particles. Neat HA particles were also functionalized with lauryl chloride for comparative purposes. Composites of PLLA/CaP-laurate were fabricated by electrospinning method. The functionalization of CaP surfaces resulted in significant improvement of the dispersion of CaP particles into the polymeric matrix, allowing inclusion of up to 40% of mineral phase without compromising its mechanical properties. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were employed to investigate the morphology of the fibers. The mass loss and calcium release of the scaffolds during degradation in phosphate buffered saline (PBS) were measured. HAD and OCP are more soluble than HA and HAD:β-TCP (7:3). The bioactivity of the composites was investigated by immersing the fibers in a simulated body fluid (SBF) at 37°C and pH 7.4. Although all PLLA/CaP-laurate can form apatite precipitation on their surface after exposition to SBF, the results demonstrate a significant enhancement in the mineralization when HAD, OCP and HAD:β-TCP (7:3) are the mineral phase in the composite instead of HA. Furthermore, mats obtained from PLLA/CaP-laurate electrospun fibers favored the mouse fibroblast cells (NIH-3T3) and stem cells from human exfoliated deciduous teeth (SHED) attachment and proliferation. Finally, PLLA/HAD-laurate and PLLA/OCP-laurate meshes showed better performance in accelerate the calcium phosphate mineralization on its surface as a result of the in vitro osteoinduction of SHEDs and calvaria derived mouse preosteoblastic cells (MC3T3-E1) if compared of those containing HA and HAD:β-TCP (7:3). These new materials are proposed as fast degradation CaP biocomposites to be used in bone regeneration applications in orthodontics and orthopedics.

Ce travail a consisté à optimiser la synthèse de phosphates de calcium (CaP) déposés sur tissus de fibres de carbone (TFC) par procédé de sono-électrodéposition afin d’obtenir des revêtements uniformes. Les paramètres électrochimiques clés optimisés sont le type et la durée de polarisation cathodique ainsi que la température de l’électrolyte. Pour un potentiel constant de -1 V à 70 °C, un régime d’électrolyse contrôlé de l’eau conduit à la formation d’un revêtement plaquettaire d’hydroxyapatite déficitaire en calcium (CDA) carbonatée. Les plaquettes sont composées de particules lamellaires (de quelques dizaines à centaines de nm) constituées de CDA carbonatée de structure ordonnée au coeur et de structure désordonnée car hydratée en surface des particules, organisation typique des apatites biomimétiques. Le matériau hybride a été dopé en strontium, engendrant la formation de revêtements où les ions Ca²+ sont substitués par des ions Sr²+ de manière contrôlée, conférant au biomatériau de nouvelles propriétés en vue d’une application en régénération osseuse. Ce travail a aussi démontré la possibilité d’adsorber de façon sélective des principes actifs ciblés (tétracycline, naproxène, aspirine) dans chaque constituant du matériau hybride. Les courbes de désorption ont mis en évidence deux modes de libération selon le principe actif.Une évaluation biologique des différentes matériaux hybrides a été réalisée. L’étude in vitro a porté sur la viabilité et la prolifération d’ostéoblastes humains en surface des biomatériaux hybrides, démontrant leur biocompatibilité. L’intérêt d’un dopage (Sr²+, aspirine et naproxène) sur l’activité des ostéoblastes a été démontré. Une expérience pilote in vivo a été menée, consistant à créer un défaut osseux dans des fémurs de rats et à étudier l’influence du type de biomatériaux TFC/CaP sur les évolutions quantitative et qualitative de la régénération osseuse
Optimization of the synthesis of calcium phosphates (CaP) on carbon fiber cloths (TFC) was performed in using sono-electrodeposition process in order to obtain uniform coatings. The electrochemical potential applied and the electrolyte temperature during the synthesis were determined as being key parameters. For a constant potential of -1 V at 70 ° C, a controlled water electrolysis regime results in the deposit of plate-like calcium-deficient apatite (CDA). This plate-like particles (from a few tens to hundreds of nm in length) consist in an ordered structure of carbonated CDA in their core and in a disordered structure in the hydrated surface, a typical organization of biomimetic apatites. The hybrid material was doped with strontium, resulting in a carbonated CDA coating where the Ca²+ ions are controllably substituted by Sr²+ ions, leading to new properties for a bone regeneration application. This work has also shown the possibility of selectively adsorb targeted active molecules (tetracycline, naproxen, aspirin) in each component of the hybrid material. The desorption curves revealed two modes of release depending on the active molecule.A biological evaluation of the different hybrid materials was carried out. The in vitro study investigated the viability and proliferation of human osteoblasts at the surface of hybrid materials, demonstrating their biocompatibility. The interest of a doping (Sr²+, aspirin and naproxen) on osteoblast activity was demonstrated. An in vivo pilot experiment was conducted, through the creation of a bone defect in rat thighbones to study the influence of TFC/CaP biomaterials on the quantitative and qualitative evolutions of bone regeneration

No presente trabalho, foram processados compósitos de polietileno de alta densidade (PEAD) com hidroxiapatita deficiente de cálcio (HA), com o objetivo de obter materiais com melhores propriedades mecânicas e bioatividade. A adição da HA deficiente de cálcio proporcionou um aumento no módulo de elasticidade (maior rigidez), menor resistência ao impacto e decréscimo do grau de cristalinidade do PEAD, proporcionando uma maior bioatividade ao material. A análise térmica exploratória (sistema não isotérmico) foi realizada por meio da técnica de calorimetria exploratória diferencial (DSC) e foram avaliados os teores de fosfato de cálcio e a velocidade de rotação da rosca no processamento dos materiais. No estudo da cristalização não-isotérmica observou-se uma diminuição da temperatura de cristalização com o aumento da taxa de resfriamento para todos os materiais sintetizados. A energia de ativação (Ea) da cristalização dos materiais foi avaliada por meio dos métodos Kissinger e Ozawa. A amostra com 5% de HA deficiente de cálcio e velocidade de processamento de 200 rpm foi a que apresentou menor valor de energia de ativação, 262 kJ/mol, menor desvio da linearidade e a que mais se assemelhou à matriz de PEAD sem HA. O teor de hidroxiapatita deficiente de cálcio não favorece o processo de cristalização devido à alta energia de ativação determinada pelos métodos descritos. Provavelmente, a velocidade de rotação, favorece a dispersão da carga na matriz de PEAD, dificultando o processo de cristalização. Na aplicação do método de Osawa-Avrami, os coeficientes de correlação indicaram perda na correlação linear. Estas perdas podem estar associadas a uma pequena percentagem de cristalização secundária e/ou à escolha das temperaturas utilizadas para determinar a velocidade de cristalização. Na determinação dos parâmetros pelo método de Mo, as menores percentagens de cristalização apresentaram um grande desvio da linearidade, com coeficiente de correlação bem menor que 1 e com o aumento da percentagem de cristalização, o desvio da linearidade diminui, ficando próximo de 1. Os resultados obtidos mostraram que o modelo de Mo e de Osawa-Avrami não foram capazes de definir o comportamento cinético dos materiais produzidos neste trabalho.
In this work, composites of high density polyethylene HDPE with calciumdeficient hydroxyapatite were synthesized in order to obtain materials with good mechanical properties and bioactivity. The addition of calcium-deficient hydroxyapatite resulted in an increase in elastic modulus (high rigidity), lower impact resistance and lower HDPE crystallinity degree, promoting, in these materials, a higher bioactivity. Scanning thermal analysis (non-isothermal system) was carried out by differential scanning calorimetry (DSC), and it was evaluated the calcium phosphate content added and the screw speed in the processing. In non-isothermal crystallization studies it was observed a decrease in crystallization temperature as the cooling rate was increased for all produced materials. The activation energy of crystallization was evaluated by Kissinger and Ozawa methods. The sample with 5 wt.% of calcium-deficient hydroxyapatite and processed at 200 rpm screw speed showed the lower value of activation energy (262 kJ/mol) and the lower deviation from linearity. Calcium-deficient hydroxyapatite does not promote the crystallization process due to the high activation energy determined by the described methods. Probably the screw speed promotes the dispersion of the filler in the HDPE matrix and hinders the crystallization process. Correlation coefficients in Osawa-Avrami method indicated loss in the linear correlation. These losses might be associated with a small percentage of secundary crystallization and/or the temperatures chosen to determine the crystallization rate. The parameters obteined from Mo method, the lower percentages of crystallization showed a great deviation from linearity, with correlation coefficient much smaller than 1, when increasing the percentage of crystallization, the deviation from linearity decreases, getting closer to 1.The results of Mo and Osawa-Avrami models were not able to set the kinetic behavior of the materials produced in this study.

It is known that muscles that lack KATP channel activity generate much greater unstimulated [Ca2+]i and force than normal muscles during fatigue. The increase in unstimulated force in KATP channel deficient muscles is abolished by a partial inhibition of L-type Ca2+ channels, suggesting that it is due to a Ca2+ influx through L-type Ca2+ channels and a subsequent increased myoplasmic Ca2+. However, there is also evidence that the increase in resting force is abolished by NAC, a ROS scavenger. The objective of this study was to reconcile these observations by studying the hypothesis that “the increase in resting [Ca2+]i during fatigue in KATP channel deficient muscles starts with an excess Ca2+ influx through L-type Ca2+ channels, followed by an excess ROS production that causes a further increase in resting [Ca2+]i”. To test the hypothesis, single FDB fibres were fatigued with one tetanic contraction/sec for 180 sec. KATP channel deficient fibres were obtained i) by exposing wild type muscle fibers to glibenclamide, a KATP channel blocker and ii) by using fibres from Kir6.2-/- mice, which are null mice for the Kir6.2 gene that encodes for the protein forming the channel pore. Verapamil, a L-type Ca2+ channel blocker, applied at 1 μM, significantly reduced resting [Ca2+]i during fatigue in glibenclamide-exposed wild type fibres. NAC (1 mM) also reduced resting [Ca2+]i in glibenclamide-exposed muscles. The results suggest that the increase in resting [Ca2+]i during fatigue in KATP channel deficient FDB fibres is due to an influx through L-type Ca2+ channels, and an excess ROS production.

Thesis (M.S.)--University of Tennessee, Knoxville, 2004.
Title from title page screen (viewed May 14, 2004). Thesis advisor: Richard Jendrucko. Document formatted into pages (ix, 77 p. : ill. (some col.)). Vita. Includes bibliographical references (p. 68-74).

碩士
國立成功大學
口腔醫學研究所
106
Peri-implantits is a major risk factor for late dental implants failures. Traditional remedy usually failed to eliminate pathogens completely due to biofilm covering the titanium surface. In this study, we developed a nano calcium-deficient hydroxyapatite (CDHA) carrier intended for extended tetracycline (TC) release to disrupt biofilm on the implant surface while simultaneously enhance new bone regeneration for peri-implantitis treatment. The tetracycline-loaded CDHA nanoparticles (TC-CDHA) were characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS) and dynamic light scattering (DLS). The TC-CDHAs were then evaluated for anti-bacteria potency by determine their minimum inhibition concentration (MIC) and minimum bactericidal concentration (MBC) of pathogens. The TC-CDHA presented as round, less than 100nm rod shape particles under SEM and TEM. The crystalline size measured by Scherrer’s formula is about 10.8nm x 4.62nm. We discovered that the loading capacity of TC was 86.23%. Tetracycline is well embedded in the CDHA as revealed by EDS examination. Anti-bacterial assay showed that the MIC of the drug loaded nanoparticles are comparable to that of the freeform TC (86.25% for TC vs. 89.47% for TC-CDHA) when both were at TC concentration of 0.1ug/ml. This study revealed that the as prepared TC-CDHA has similar potency as freeform TC while may harbor additional advantages for stimulating bone regeneration. Such nanomedicine holds a promising future for peri-implantitis treatment.

碩士
大同大學
材料工程學系(所)
107
Development of biocompatible and multifunctional nanovehicle has recently attracted much attention for cancer theranostics. In this study, super paramagnetic iron oxide nanoparticle (SPION) nanorod clusters coated with europium doping calcium-deficient hydroxyapatite- polyethylenimine (Eu:de-HAP-PEI) are synthesized through co-precipitation process to form core/shell nanostructure. The luminescent SPION@Eu:de-HAP-PEI nanorods are explored for the loading and controlled delivery of drugs. The photoluminescence (PL) intensity of SPION@Eu:de-HAP-PEI nanorods can be adjusted by varying Eu3+ concentrations. The magnetic property of SPION@Eu:de-HAP-PEI nanorods increase with the increase of SPION weight ratio. More importantly, the SPION@Eu:de-HAP-PEI nanorods show high drug encapsulation capacity and sustained drug release profile, which is governed by diffusion phenomenon. The SPION@Eu:de-HAP-PEI nanorods exhibit magnetic-targeted characteristic, high drug loading content, high toxicity to tumor cells, low side effects to normal cells, and PL imaging functions. These findings prove that the SPION@Eu:de-HAP-PEI nanorods have great potential as novel tumor-targeting theranostic agents for simultaneous PL imaging and efficient anti-tumor treatment.

To repair massive bone defects caused by disease and trauma, a bone grafting procedure is required. The limitations associated with the use of autografts (tissue grafts from one point to another of the same individual's body) and allografts (tissue grafts between genetically nonidentical individuals) have boosted the research and development of bone graft substitutes. Calcium phosphate cement (CPC) is a promising bone graft substitute because of its bioactivity, osteoconductivity and bone replacement capability. However, difficulties with injectability and slow resorption rate have limited the wider applications of CPC. To overcome these limitations, premixed and injectable calcium deficient apatite biocement (cd-AB) were prepared in the initial phase of this study. Using a non-aqueous solution as the liquid phase, the resulting premixed cd-AB had the advantage of remaining stable in the syringe and only hardened following delivery to the defect site. As well, when injected into an aqueous environment, this premixed cd-AB exhibited improved washout resistance when compared to the conventional cd-AB using water as the liquid phase. However, the premixed cd-AB required a longer setting time and developed a reduced compressive strength compared to the conventional cd-AB. The hydration products of premixed cd-AB were a mixture of calcium deficient hydroxyapatite (cd-HA) and PLA. In vitro Tris-HCl immersion tests demonstrated that the premixed cd-AB was degradable. The results revealed that the premixed cd-AB was cytocompatible and no adverse effects were observed after attachment and proliferation of MG-63 osteoblast-like cells in vitro. The most distinct advantages of premixed and injectable PLA-modified cd-AB were its excellent washout resistance and in vitro degradability, suggesting that it may be a promising candidate for future bone reconstruction. In recent years, bone tissue engineering has emerged as a promising approach for the repair of bone damage and defects. In this approach, a scaffold is normally used alone or in combination with growth factors and/or cells to guide bone regeneration. Among the synthetic polymers used as scaffold materials, poly(ε-caprolactone) (PCL) has been widely used given its excellent biocompatibility and ease of processing. However, the use of PCL scaffolds is limited as a consequence of potential drawbacks including a slow degradation rate and their hydrophobic surface. These disadvantages may be overcome by incorporating additional natural polymer or inorganic fillers into the PCL matrix. In the second section of this study, porous scaffolds of zein/PCL biocomposite were fabricated and characterized. These scaffolds were prepared using the particulate leaching method with sodium chloride particles as porogen. Porous biocomposite scaffolds with porosity around 70% and well-interconnected network were obtained. The incorporation of zein into PCL led to an improvement of the surface hydrophilicity as confirmed by the results of water contact angle measurement. Following immersion in a phosphate buffered saline solution (PBS) in vitro for 28 days, it was observed that the zein/PCL scaffolds degraded more rapidly than the PCL scaffolds and the degradation rate could be controlled by adjusting the amount of zein in the composite. These results demonstrated the potential of the zein/PCL biocomposite scaffolds to be exploited in tissue engineering strategies for the repair of bone defects. In the final section of this study, porous scaffolds using a magnesium phosphate (MP)/PCL biocomposite were developed for bone tissue engineering applications. The composite scaffolds were fabricated by the particulate leaching method again using sodium chloride particles as porogen. The resulting scaffolds had interconnected macroporous structure with porosity around 73%. The surface hydrophilicity of the scaffolds was enhanced by the incorporation of MP component and confirmed by water contact angle measurement. The results from subsequent in vitro degradation experiments showed that the MP/PCL composite scaffolds degraded faster than PCL scaffolds in a PBS solution. An additional benefit was that the degradation rate of the scaffolds could be tuned by adjusting the content of MP component in the composite. These results indicated that the MP/PCL composite scaffolds have potential application in bone tissue engineering.
Thesis (Ph.D.) -- University of Adelaide, School of Chemical Engineering, 2013

碩士
長庚大學
醫學生物技術研究所
94
Glucose-6-phosphate dehydrogenase (G6PD) is involved in the generation of NADPH for the proper maintenance of the cellular redox balance, G6PD deficiency predispose human fibroblasts (HFF) to retarded growth and accelerated cellular senescence. Thus far, the pivotal role of a micronutrient, such as folic acid, on the cellular functions of the normal and G6PD-deficient HFF have never been investigated. The objectives of the present research are two-fold: (1) To explore the possibility that folic acid deficiency can trigger the occurrence of apoptotic cell death in G6PD-deficient as well as G6PD-normal HFFs. Emphasis will be to elucidate if folate deficiency-induced apoptosis involves reactive oxygen species (ROS)-mediated mitochondrial calcium overload pathway; (2) Real time analysis of living intact cell in single cell level to address the questions if glutathione (GSH) depletion and lipid peroxidation are involved in the very early responses of both HFF-1 and HFF-3 fibroblasts to folate deficiency-induced apoptosis using probe-based confocal fluorescence imaging technique. Furthermore, the possibility as to whether or not the mitochondria calcium overload plays a pivotal role in arbitrating apoptotic process will be addressed in this project. Using DCF-DA as the fluorescence probe, we first monitored the production of mitochondrial ROS (mROS) in both types of fibroblasts cultivated under folate-deficiency condition. Our data indicated that HFF-1 cells (G6PD-deficient cells) produced substantially higher amounts of mROS than their folate-sufficient counterparts (HFF-3 cells) cultivated under folate-deficiency condition seven days. Next, using CMF-DA and BODIPY as the probes, we can able to attest that the folate-deficiency condition (7th day) could elicit GSH depletion and lipid peroxidation in the very early response of both types of fibroblasts to folate-induced oxidative stress situation. Using Fluo-4 (for cytosolic Ca++ probe ) and Rhod-2 (for mitochondrial Ca++ probe) as the probes, we also measured the temporal and spatial distribution of Ca++. In this study, we found that only HFF-1 cells had had increased quantity of Ca++ accumulation as reflected by the increased exhibition of the Rhod-2-mediated orange colored fluorescence. These data attested that mitochondrial calcium overload (mCa++) was the major contributing factor for increased susceptibility of HFF-1 cells to folate deficiency-induced apoptosis as compared to their folate-sufficient counterparts. In parallel, we also found out that increased mCa++ levels correlated with the loss of mitochondrial membrane potential (Δψm). Taken together, our data indicated folate-deficient fibroblasts was mediated via early ROS-evoked GSH depletion and lipid peroxidation and lipid peroxidation resulting in membrane damages. This was followed by a sudden inflex of Ca++ into mitochondria and thus Δψm changed leading to the eventual occurrence of apoptosis. G6PD-deficeincy rendered fibroblasts more prone to folate deficiency-induced apoptosis because of the double stresses situation imposed on these cells.

An increase in cytosolic Ca2+ levels ([Ca2+]i) is a key event that occurs downstream of many signaling cascades in response to an external stimulus and regulates a wide range of cellular processes, including platelet activation. Eukaryotic cells increase their basal [Ca2+]i allowing extracellular Ca2+ influx into the cell, which involves different mechanisms. Store-operated Ca2+ entry (SOCE) is considered the main mechanism of extracellular Ca2+ influx in electrically non-excitable cells and platelets, and comprises an initial Ca2+ depletion from intracellular Ca2+ stores prior to activation of extracellular Ca2+ influx. Although the close relation between Ca2+ release from intracellular stores and extracellular Ca2+ influx was clear, the nature of the signal that linked both events remained elusive until 2005, when Stromal Interaction Molecule 1 (STIM1) was identified as an endoplasmic reticulum (ER) Ca2+ sensor essential for inositol (1,4,5)-trisphosphate (IP3)-mediated SOCE in vitro. However, the function of its homologue STIM2 in Ca2+ homeostasis was in general unknown. Therefore, mice lacking STIM2 (Stim2-/-) were generated in this work to study initially STIM2 function in platelets and in cells of the immune system. Stim2-/- mice developed normally in size and weight to adulthood and were fertile. However, for unknown reasons, they started to die spontaneously at the age of 8 weeks. Unexpectedly, Stim2-/- mice did not show relevant differences in platelets, revealing that STIM2 function is not essential in these cells. However, STIM2 seems to be involved in mammary gland development during pregnancy and is essential for mammary gland function during lactation. CD4+ T cells lacking STIM2 showed decreased SOCE. Our data suggest that STIM2 has a very specific function in the immune system and is involved in Experimental Autoimmune Encephalomyelitis (EAE) at early stages of the disease progression. Stim2-/- neurons were also defective in SOCE. Surprisingly, our results evidenced that STIM2 participates in mechanisms of neuronal damage after ischemic events in brain. This is the first time that the involvement of SOCE in ischemic neuronal damage has been reported. This finding may serve as a basis for the development of novel neuroprotective agents for the treatment of ischemic stroke, and possibly other neurodegenerative disorders in which disturbances in cellular Ca2+ homeostasis are considered a major pathophysiological component
Der Anstieg des cytosolischen Ca2+-Spiegels ([Ca2+]i) ist ein Schlüsselereignis, das vielen Signalkaskaden, durch extrazellulären Stimulus ausgelöst werden, nachgeschalten ist, und eine große Reihe zellulärer Prozesse reguliert, z.B. die Aktivierung von Blutplättchen. Eukaryotische Zellen erhöhen ihren basalen ([Ca2+]i) durch Einstrom von extrazellulärem Ca2+ in die Zelle hinein, was durch verschiedene Mechanismen geschehen kann. Store-operated Ca2+-entry (SOCE), wird als der Hauptmechanismus für den Einstrom von extrazellulärem Ca2+ in nicht elektrisch-erregbaren Zellen sowie Plättchen angesehen und beinhaltet einen initialen Ca2+-Ausstrom aus intrazellulären Speichern der dem Ca2+-Einstrom aus der Extrazellulärraum vorrausgeht. Obwohl die Beziehung zwischen Ca2+-Ausstrom aus intrazellulären Speichern und extrazellulärem Ca2+-Einstrom über die Plasmamembran viele Jahre bekannt war, so blieb doch das beide Ereignisse verknüpfende Element unbekannt. Im Jahre 2005 jedoch wurde Stromal Interaction Molecule 1 (STIM1) als Ca2+-Sensor des endoplasmatischen Retikulums (ER) und als essentieller Bestandteil für inositol(1,4,5)-triphosphat (IP3)-vermittelten SOCE in vitro identifiziert. Die Funktion seines Homologs, STIM2, in der Ca2+ Homeostase blieb jedoch unklar. Aus diesem Grund generierten wir STIM2-defiziente (Stim2-/-) Mäuse um die Funktion dieses Proteins in Blutplättchen und Immunzellen untersuchen zu können. Bis zum Erwachsenenalter entwickelten sich Stim2-/- Mäuse normal in Bezug auf Größe und Gewicht und waren fertil. Jedoch sterben die Tiere spontan aus unbekannten Gründen, beginnend ab einem Alter von 8 Wochen. Unerwarteter Weise, zeigten Stim2-/- Mäuse keine maßgeblichen Funktionsunterschiede in Plättchen, was eine essentielle Funktion von STIM2 in diesen Zellen ausschließt. Jedoch scheint STIM2 in die Entwicklung der Brustdrüsen während der Schwangerschaft involviert und essentiell für die Brustdrüsenfunktion während der Säugephase zu sein. Darüberhinaus zeigten STIM2 defiziente CD4+ T-Zellen einen verminderten SOCE. Weiter deuten unsere Daten auf eine spezifische Funktion von STIM2 im Immunsystem hin, mit einem Einfluss auf die frühen Phasen und das Fortschreiten der Experimentellen Autoimmun-Enzephalomyelitis (EAE). Stim2-/- Neuronen wiesen ebenso wie CD4+ T-Zellen einen gestörten SOCE auf. Desweiteren belegen unsere Ergebnisse, dass STIM2 überrascherweise an den Neuronen zerstörenden Mechanismen nach ischämischen Ereignissen des Gehirns mitwirkt. Dies ist die erste Studie, die von einer Beteiligung von SOCEan ischämischen neuronalen Schäden berichtet. Diese Entdeckungen können vielleicht als Basis für die Entwicklung neuer neuroprotektiver Medikamente bei ischämischen Schlaganfall dienen - und möglicherweise auch bei anderen neurodegenerativen Erkrankungen, bei denen Störungen der zellulären Ca2+ Homöostase als hauptsächliche pathophysologische Komponente angesehen werden