Search

Electrochemical synthesis of nanosized monetite powder was performed galvanostatically from homogeneous Solution of Na(2)H(2)EDTA center dot 2H(2)O, NaH2PO4 and CaCl2 at a concentration relationship Ca/EDTA/PO43- of 0.25/0.25/0.15 M at current density of 137 mA cm(-2) and pH value of 5.0. The synthesized monetite powder was characterized by X-ray diffraction, infrared spectroscopy, size distribution measurements, thermogravimetric and differential thermal analysis and scanning electron microscopy. Monetite powder was electrophoretically deposited on titanium from ethanol Suspension, using constant voltage method. The deposition was performed at constant voltage between 10 and 50 V and for a constant deposition time between 1 and 30 min. The influence of the applied voltage and deposition time on the mass and morphology of monetite deposits was investigated. It was shown that monetite deposits of the highest thickness and the lowest porosity can be formed at lower applied voltage (30 V) and for longer deposition time (20 min) and then converted to hydroxyapatite. (C) 2009 Elsevier B.V. All rights reserved.

Cilj ove doktorske disertacije je dobijanje prahova i prevlaka kalcijum-fosfata na titanu primenom elektrohemijskih metoda, kao i ispitivanje uticaja parametara sinteze (gustina struje, napon, pH vrednost rastvora, vreme taloženja) na fazni sastav, veličinu kristalita i morfologiju dobijenih prahova i prevlaka. Elektrohemijskom sintezom iz rastvora Na2H2EDTA·2H2O, NaH2PO4 i CaCl2 sa odnosom koncentracija Ca/EDTA/PO43− od 0,25/0,25/0,15 M uspešno su dobijeni prahovi monetita i hidroksiapatita. Ispitan je uticaj pH vrednosti polaznog rastvora i gustine struje na vrstu sintetisanog kalcijum-fosfata, morfologiju i termičko ponašanje prahova različitim metodama kao što su rendgenska difrakcija na polikristalnom uzorku, skenirajuća elektronska mikroskopija, diferencijalno termijska i termogravimetrijska analiza i infracrvena spektroskopska analiza. Pri pH vrednosti od 5,0 i gustini struje od 137 mA cm-2 dobijen je nanodimenzioni prah monetita sa veličinom kristalita od 27,1 nm. Sintezom prahova pri pH vrednostima od 9,0 i 12,0 i pri gustinama struje od 137 mA cm-2 i 207 mA cm-2 dobijeni su prahovi hidroksiapatita sa veličinom kristalita u intervalu od 21,6 do 24,3 nm, čime je pokazano da pH vrednost i gustina struje ne utiču značajno na veličinu kristalita. Na morfologiju elektrohemijski sintetisanih prahova hidroksiapatita ne utiče promena gustine struje, ali utiče pH vrednost rastvora. Pri manjoj pH vrednosti od 9,0 se dobijaju prahovi sa sfernim aglomeratima, dok se pri većoj pH vrednosti od 12,0 dobijaju prahovi sa pločastim aglomeratima. Temperatura termičke dekompozicije nanočestičnog praha monetita na kalcijum-pirofosfat i vodu je niža (1260 °C) u odnosu na literaturni podatak (1353 °C), zbog velikog odnosa specifična površina/zapremina nanočestičnog praha. Uslovi elektrohemijske sinteze ne utiču značajno na termičko ponašanje prahova hidroksiapatita. Prevlake monetita dobijene su elektroforetskim taloženjem iz etanolske suspenzije elektrohemijski sintetisanog praha monetita i ispitan je uticaj napona (10-50 V) i vremena taloženja (1-30 min) na masu i morfologiju prevlake. Masa prevlake, srednji prečnik pora, srednja površina pora i poroznost prevlaka zavise... The aim of this PhD thesis was to prepare nanosized calcium-phosphate powders and coatings using electrochemical methods and to investigate the effect of experimental parameters (e.g. applied current density, solution pH value, applied voltage, deposition time) on the phase composition, crystallite domain size, morphology and thermal characteristics of obtained powders and coatings. Electrochemical synthesis of nanosized monetite and hydroxyapatite powders were performed galvanostatically from homogeneous solution of Na2H2EDTA∙2H2O, NaH2PO4 and CaCl2 at a concentration relationship Ca/EDTA/PO43− of 0.25/0.25/0.15M. The influence of the solution pH and applied current density on the phase composition, morphology and thermal behavior was investigated by X-ray diffraction, infrared spectroscopy, size distribution measurements, thermogravimetric and differential thermal analysis, scanning electron microscopy and transmission electron microscopy. At current density of 137 mA cm−2 and pH value of 5.0 monetite powder was synthesized. The crystallite domain size of powder was calculated to be 27.1 nm. At current densities of 137 and 207 mA cm−2 and pH values of 9.0 and 12.0 hydroxyapatite powders were synthesized with crystallite domain size in the range from 21.6 to 24.3 nm, meaning that pH values as well as applied current densities does not affect significantly the crystallite domain size. The morphology of synthesized hydroxyapatite powders were not influenced by current density, but on the other hand are influenced by solution pH. Powders synthesized at lower pH value consist of spherical agglomerates, while powders synthesized at higher pH value have the plate-like structure. The temperature of phase transformation from monetite to calcium pyrophosphate was lower (1260 °C) in comparison with literature data (1353 °C), due to high surface-to-volume ratio of nanosized powder. The parameters of electrochemical synthesis of hydroxypatite powders do not affect significantly the thermal behavior. Monetite coatings were electrophoretically deposited from ethanol suspension of electrochemically synthesized monetite powder, using constant...

More than one million people worldwide receive some kind of bone graft each year. Grafts are often needed following bone tumour removal or traumatic fractures to fill voids in the bone and to aid in the healing process. The most common method involves bone transplantation, in which bone tissue is taken from one site to fill the defect in another site. The procedure thus involves two surgeries, which leads to an increased risk of complications. New, synthetic graft materials that can be used to fill defects and minimise the complications associated with bone tissue harvesting are therefore necessary. The synthetic materials available today lack the inherent biological factors of bone that stimulate the bone regeneration process. Much of today’s research concerning synthetic bone graft materials aims to solve this issue and researchers have suggested several different strategies. The purpose of this thesis is to improve the performance of acidic calcium phosphate cements, which are materials used as synthetic bone grafts. By combining these cements with drugs or ion additives, local delivery could be achieved with the potential to stimulate bone formation. Two different combinations were attempted in this thesis: cement in combination with simvastatin, or cement in combination with strontium halide salts. Both simvastatin and strontium are known to positively affect bone formation. The efficacy of the cements with the additives was evaluated using different bone cell cultures. The results regarding simvastatin showed that the cement’s mechanical property was not affected upon drug loading, and that the drug was released by a diffusion-controlled mechanism. Moreover, results showed that simvastatin stimulated the bone-forming cells (osteoblasts) to produce more bone tissue, while it inhibited bone-degrading cells (osteoclasts) from degrading the cement. These findings suggest that simvastatin could aid in the bone regeneration process in the local area surrounding the cement. The main purpose of the study using strontium halide salts was to increase the cement’s X-ray contrast, which is a property used to monitor cement during injection. In addition, strontium is believed to positively affect bone cells. The X-ray contrast did increase after the addition of 10 wt% strontium bromide or strontium iodide, while the cell study results did not indicate any significant effects on the bone-forming cells. In the last section of this thesis, zebrafish were used as a model to evaluate bone formation upon treatment with degradation products from synthetic bone grafts. The zebrafish is a small organism with 70 % gene homology to humans; due to its transparency, fast development and ease of handling, it is an interesting model for high-throughput studies. Silicate, which is an ionic degradation product of many different bone substitute materials, was used as a proof-of-concept to visualise bone formation in these fish. The results showed an increased bone formation upon treatment with 0.625 μM silicate ions. The results suggest that this model could be used as a complement to bone cell culture studies in pre-clinical evaluations of the degradation products of bone substitute materials, thus helping researchers to design materials with degradation products that could stimulate bone formation.

International audience; This study evaluated the in vivo behavior of an injectable calcium phosphate bone cement implanted in bone defects at the distal end of rabbit femora. After 3 weeks, samples were harvested and processed for undecalcified sectioning. Scanning electron microscopy, transmission electron microscopy, and Fourier transform infrared microspectroscopy showed direct contact of bone and cement without soft tissue interposition, biocompatibility, and bioactivity with osteoconductive properties.

Se estudiaron cinco variaciones del procedimiento de síntesis de monetita modificando la agitación, la velocidad de adición de ácido fosfórico, la homogenización y la temperatura de secado. Los productos se caracterizaron por difracción de rayos X (DRX), microscopía electrónica de barrido (SEM-EDS), relación Ca/P (por titulación de calcio con permanganato de potasio y valoración colorimétrica de fósforo por la formación del complejo azul de molibdeno) y espectroscopía infrarroja con transformada de Fourier (FTIR). Los resultados de DRX, espectroscopia infrarroja y la relación Ca/P señalan que el fosfato sintetizado corresponde a monetita pura. Se encontró que los factores de síntesis que más afectan las propiedades de composición, estructura cristalina, relación Ca/P y forma y tamaño de grano de los fosfatos sintetizados son la relación estequiométrica de los reactantes y la mecanoactivación de sólido con sobrenadante. Five variations of the monetite (M) synthesis were evaluated modifying the stirring, the phosphoric acid addition rate, the homogeneity and the drying temperature. Products were assessed by means of XRD, FTIR, SEM-EDS analysis and chemical assay of Ca/P (calcium by titration with potassium permanganate and phosphorus by colorimetric assessment of the molybdenum blue complex). X-ray diffraction, infrared spectroscopy and Ca/P ratio indicate that the synthesized phosphate corresponds to pure monetite. It was found that the most influential factors affecting composition, crystal size and Ca/P were stoichiometry and ballmilling mechanoactivation.

Brushite forming calcium phosphate cements receive growing interest in hard tissue scaffold applications due to their high surface area and high bioresorbability. The finer microstructure of monetite, the dehydrated form of brushite, has attracted attention for bone tissue engineering applications. The reduction in brushite content of the b-tricalcium phosphate-monocalcium phosphate monohydrate cement system by selective inhibition of growth upon addition of citric acid to excess setting liquid was investigated. The relaxation period during cement setting was monitored by pH stat titration and free drift runs. Spectrometric analysis revealed that the change in solubility of calcium phosphates upon addition of citric acid caused the inhibition of brushite formation and promotion of monetite precipitation. Dissolution of monetite crystals was insensitive to citrate adsorption despite their lower surface area compared to brushite. Overall brushite/ monetite ratio decreased consistently with increasing citric acid concentration in the of 0?1-0?5M range.

Tissue engineering–based bone grafts are emerging as a viable alternative treatment modality to repair and regenerate tissues damaged as a result of disease or injury. The choice of the biomaterial component is a critical determinant of the success of the graft or scaffold; essentially, it must induce and allow native tissue integration, and most importantly mimic the hierarchical structure of the native bone. Calcium phosphate bioceramics are widely used in orthopaedics and dentistry applications due to their similarity to bone mineral and their ability to induce a favourable biological response. One such material is monetite, which is biocompatible, osteoconductive and has the ability to be resorbed under physiological conditions. The osteoinductive properties of monetite in vivo are known; however, little is known of the direct effect on osteoinduction of human mesenchymal stem cells in vitro. In this study, we evaluated the potential of monetite to induce and sustain human mesenchymal stem cells towards osteogenic differentiation. Human mesenchymal stem cells were seeded on the monetite scaffold in the absence of differentiating factors for up to 28 days. The gene expression profile of bone-specific markers in cells on monetite scaffold was compared to the control material hydroxyapatite. At day 14, we observed a marked increase in alkaline phosphatase, osteocalcin and osteonectin expressions. This study provides evidence of a suitable material that has potential properties to be used as a tissue engineering scaffold.

International audience; In this report new hybrid materials based on brushite-alginate and monetite-alginate were prepared by self-assembling alginate chains and phosphate source ions via a gelation process with calcium ions. The alginate served as nanoreactor for nucleation and growth of brushite or/and monetite due to its gelling and swelling properties. The alginate gel framework, the crystalline phase and morphology of formed hybrid biomaterials were shown to be strongly dependent upon the concentration of the phosphate precursors. These materials were characterized by thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive x-ray analysis (EDX).

Premixed calcium phosphate cements (pCPC), where glycerol is used instead of water as mixing liquid, present better handling characteristics than water-based cements. However, the setting mechanisms of pCPC have not been described thoroughly. The aim of this paper is to increase the understanding of the setting mechanism of pCPC. The investigated cement starts to set when glycerol is exchanged with water via diffusion of glycerol out to the surrounding body fluid and water into the material. To better understand the water-glycerol exchange a method was developed where the setting depth of the cement was measured over time. Thermo gravimetric analysis (TGA) was used to determine the liquid exchange rate during setting. To study the influence of temperature on the crystalline end product, pCPC and water-mixed calcium phosphate cement (wCPC) were set at different temperatures and analyzed with X-ray diffraction (XRD). The setting depth measurements showed that the set layer of the pCPC grew with a speed proportional to t0.51 at 37°C. TGA results furthermore showed that less than 10% of the glycerol remained after 16 hours. Setting of pCPC at different temperatures showed that mainly brushite was formed at 5°C, a mixture of brushite and monetite at 21°C and mainly monetite at 37°C. It furthermore showed that brushite was the main phase after setting of wCPC, but some monetite was present in these cements. The study presents a new method for evaluation of pCPC that increases the understanding of their setting mechanism. Furthermore, the XRD results indicate that storage at 5°C could improve the shelf life of acidic pCPC. Detta är den omarbetad versionen av artikeln ursprungligen inskickad till "Journal of Biomedical Materials Research. Part B - Applied biomaterials".

Calcium phosphate ceramics have been investigated due their properties such as absence of toxicity and biocompatibility, enabling their use in medicine field being applied as a substitute for bone implants. However, other characteristics are required such as bioaffinity, mechanical and chemical resistances. Due to the difficulty of obtaining such properties in the pure phosphates, composites were proposed by combining the mechanical and physical properties of bio inert materials to the biological properties of bioceramics. In this work, nanocomposites of calcium phosphates and titanium oxide were synthesized, by the controlled hydrolysis of titanium tetrabutoxide in compositions between 1 and 10% in aqueous solutions of calcium chloride and ammonium phosphate. The solids were characterized by X-ray diffraction, infrared spectroscopy, thermogravimetric analysis and scanning electron microscopy. The results showed the incorporation of titanium oxide onto phosphate surface without loss of crystallinity and morphological changes. Evaluation of chemical stability of the nanocomposites showed that they were resistant to dissolution at pH below 6.0. The bioactivity tests showed that the nanocomposite containing 2% of titanium oxide was performed better than others Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES As cerâmicas de fosfato de cálcio têm sido investigadas devido as suas propriedades tais como biocompatibilidade e ausência de toxicidade, possibilitando sua utilização na área médica sendo aplicadas como substituto do tecido ósseo em implantes. No entanto, outras características são importantes tais como bioafinidade, resistência mecânica e química. Devido à dificuldade de se obter tais propriedades nos fosfatos puros, nanocompósitos foram propostos por combinarem as propriedades mecânicas e físicas dos materiais bioinertes com as propriedades biológicas das biocerâmicas. Assim neste trabalho, nanocompósitos do fosfato de cálcio monetita (CaHPO4) com dióxido de titânio foram sintetizados pela hidrólise controlada de tetrabutóxido de titânio em composições variando de 1 a 10% em soluções aquosas de cloreto de cálcio e fosfato de amônio. Os sólidos foram caracterizados por difratometria de raios-X, espectroscopia na região do infravermelho, análise termogravimétrica e microscopia eletrônica de varredura. Os resultados mostraram que houve uma incorporação do dióxido de titânio na superfície da monetita sem perda da cristalinidade e alteração morfológica. A avaliação da estabilidade química dos materiais mostrou que os nanocompósitos apresentaram resistência à dissolução em pH abaixo de 6,0. Os ensaios de bioatividade indicaram que o nanocompósito M2 apresentou melhor desempenho que os demais

Calcium phosphate cements are used in medicine to fill bone defects or give support to screws and plates in fracture fixation. The cements are formed via mixing a powder with water and the mixture harden through a dissolution-precipitation reaction. Today the cement mixing is performed in the operating room and consists of several complicated steps that need to be performed under sterile conditions. This renders the mixing a risk factor, potentially leading to harm for the patient e.g. unsatisfactory healing or infection. To reduce this risk, premixed cements have been developed using glycerol as mixing liquid. The premixed cement sets when it is exposed to body liquids. Therefore, premixed cement can be delivered to the operating room in prefilled syringes ready for use, thus eliminating the mixing step. The aim of this thesis is to describe differences between premixed and water-mixed cements and their advantages and drawbacks. The differences will be discussed based on results obtained from bench testing of specific cement properties as function of cement formulations as well as in vitro and in vivo studies. Several cement formulations were evaluated e.g. the influence of powder to liquid ratio (P/L), powder particle size and addition of water on key properties. The results showed that premixed cements have excellent handling properties and have mechanical properties similar to water-based cements. Both P/L and particle size can be used to control these properties. It was shown that small amounts of water improve certain cement properties while dry raw materials were important for long shelf life. To better understand the setting of premixed cements new methods for evaluating working time and setting of premixed cements were developed. In vivo studies showed that the formulations developed in this thesis are biocompatible, resorbable and show good tissue response in bone. This thesis concludes, that the premixed cements are a promising biomaterial with excellent handling properties and good biological response. The most important challenge for the premixed cements, in order to become commercially successful, is to obtain clinically relevant setting time and shelf life simultaneously. An increasing use of premixed cements in the clinics should shorten operation times and reduce infection rates to the benefit of both patients and medical staff.

High temperature hydrothermal syntheses, using calcium nitrate tetrahydrate, sodium dihydrogen phosphate and urea as precursors, and characterization of hydroxyapatite (HAp) whiskers are reported herein. The morphology and chemical composition of the crystals from a monetite to a hydroxyapatite phase were controlled by varying the starting concentrations of the precursors and the solution pH through the amount of urea that is decomposed during heating. X-ray diffraction (XRD) analysis, infrared spectroscopy (IR), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM) and high-resolution TEM (HRTEM) were used to investigate the products of the syntheses in order to find the optimum reaction conditions for obtaining the desired morphology and phase composition. Different morphologies ranging from single crystals of monetite through rods and plates of hydroxyapatite with different size distribution to whisker-like single hydroxyapatite crystal were achieved by simply varying the starting concentration of urea. Structural refinement of the hydroxyapatite whiskers confirmed a strong preferential orientation along the c-axis direction of the hexagonal crystal structure, which was significantly different from the usually observed random crystal orientation. TEM and SEM analysis of the apatite whiskers confirmed single crystal structure with the a c-axis orientation parallel to the long axis of the whiskers, with sizes up to 150 mu m in length, 10 mu m in width and with a thickness of about 300 nm, that grew from the same centre of nucleation, forming flaky-like particles. (C) 2010 Elsevier Ltd and Techna Group Sri. All rights reserved.

La presente Tesis Doctoral se titula "Obtención y caracterización de nuevos cementos óseos de fosfatos de calcio en el sistema DCP―alfa-TCP". Los cementos de fosfatos de calcio (CFC) son materiales biocompatibles que tienen la propiedad de endurecer en condiciones fisiológicas formando una estructura porosa de cristales interconectados de hidroxiapatita, i.e. la fase mineral de los tejidos óseos. Estos materiales pueden ser diseñados para que sean inyectables y tengan distintos porcentajes de porosidad. Este hecho permite obtener cementos con distintas tasas de reabsorción ósea que pueden aplicarse con técnicas de mínima invasión. En general, estas propiedades otorgan a estos biomateriales un excelente interés en campos de aplicación de prevención, reconstrucción o estabilización ósea (p.e.: osteoporosis, cirugía craneofacial, vertebroplastia, cifoplastia).Esta Tesis Doctoral consta de 6 capítulos. El Capítulo 1 (Cementos óseos de fosfatos de calcio) recoge el estado del arte de los CFC. Se realiza una revisión bibliográfica crítica de toda la información de interés. Se concluye la necesidad de realizar estudios cinéticos que expliquen adecuadamente las propiedades de fraguado de estos cementos y permitan diseñar cementos con mejores propiedades. El Capítulo 2 (Materiales y métodos utilizados en la fabricación y caracterización de cementos óseos de fosfatos de calcio) describe el protocolo de trabajo seguido para caracterizar los CFC física y químicamente. Este protocolo permite establecer correlaciones entre la microestructura y las propiedades macroscópicas. El Capítulo 3 (Estudio de la cinética de la reacción de fraguado de un cemento óseo de fosfato de calcio) investiga la cinética de fraguado de un cemento octocálcico en el sistema DCP―alfa-TCP. Los resultados mostraron que: (a) sólo el alfa-TCP reaccionó para dar una hidroxiapatita deficiente en calcio (CDHA); (b) el porcentaje de reacción y la resistencia mecánica a compresión estaban correlacionadas; (c) el cemento presentó una estructura de cristales interconectados con distinto grado de compacidad. El Capítulo 4 (Estudio de nuevas formulaciones de cementos de fosfatos de calcio en el sistema DCP―alfa-TCP) investiga las propiedades de fraguado y de resistencia mecánica de cementos del sistema DCP―alfa-TCP en el intervalo de relaciones Calcio/Fósforo (Ca/P) 1.26

© 2014, Australasian Ceramic Society. All rights reserved. Biogenic materials like corals, which are readily available, could be used to produce bioceramic materials and address significant advantages due to their unique structures and chemical compositions that contain Mg and Sr. Many conversion processes has been in the past proposed. In this work, a comparison study between the conversion of coral with orthophosphoric acid and ammonium dihydrogen phosphate was conducted. The resultant structures and compositions were studied using XRD, ICP-MS, SEM and FTIR. The results show that with phosphoric acid the coral was converted into mainly monetite (92%). The ammonium dihydrogen phosphate converted approximately 76% of the coral to hydroxyapatite through solid state reactions. The two routes proved to be effective in producing bioceramic materials from corals under moderate conditions of temperature with a basic condition favouring the yield of hydroxyapatite.