Bioceramics 27

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Authors: T.S. Sampath Kumar
Abstract: The development of the calcium phosphate ceramics (CPC) using natural materials such as coral, eggshell, bovine bone, fish bone etc., from Indian origin have been reviewed. The CPCs from natural sources has the benefit that they inherit some of the properties of the raw materials such as the macro-and micro-pore structure, optimal composition, similar morphology etc., as well as the advantage of unlimited world wide availability at a very low raw material cost. Hydroxyapatite (HA), carbonated HA and fluorapatite from natural coral genus "Gonioporahas been obtained. Growth factor loaded coralline HA has been found to significantly accelerate early-stage bone formation in in vivo rabbit model studies. Sea shells have been tested as the source of calcium for electrochemical deposition of HA on titanium implants. Deproteinized hydroxyl carbonate apatite phase was formed by heating adult bovine tibia at 500o C. As eggshell could be easily procured, a great deal of effort has been made to utilize this resource as value-added CPCs including nanocrystalline HA (OHA), calcium deficient HA (CDHA), TCP, tetracalcium phosphate (TTCP) etc., which are the most widely used bone substitutes. Also OHA showed higher antibiotic delivery and more controlled protein release profile compared to the synthetic apatites. Eggshell derived CPCs were also found to have minor amount of Mg, Sr, Si and Na ions inherited from the eggshell. As these ions are crucial for bio-mineralization of eggshell, the influence of multi-ions substituted CPCs as a potential bioceramic for bone regenerative applications has been emphasised.
Authors: Arief Cahyanto, Kanji Tsuru, Kunio Ishikawa
Abstract: Apatite cement (AC) is a breakthrough in biomaterials for the reconstruction of the bone defect. However, the replacement of AC to bone up to the present time is still controversial for researchers. Several researchers have reported that AC was replaced by bone while others claimed replacement was limited. The aim of this study is to investigate the transformation mechanism of AC to B-type carbonate apatite (CO3Ap) using different atmosphere. An in vitro study mimicking the body environment was employed in order to examine the effect of setting atmosphere on the composition of set AC. An equimolar of tetracalcium phosphate (TTCP; Ca4(PO4)2O) and dicalcium phosphate anhydrous (DCPA; CaHPO4) mixed with distilled water was enabled to harden at 37°C and 100% of relative humidity under presence of 5% CO2, 100% CO2, and 100% N2 atmospheres. XRD and FT-IR analyses revealed that in the presence of 100% CO2 and 5% CO2, B-type CO3Ap could be determined and only small amounts of TTCP remained unreacted. On the contrary, in the presence of 100% N2, the CO32- bands could not be detected and larger amount of TTCP remained unreacted compared to 5% CO2 and 100% CO2 atmospheres. SEM morphology showed that the microstructure of AC was entangled and locked to each other. In addition, the small needle like crystals appeared in the surface of 100% N2, similar to hydroxyapatite. We concluded that the CO32- ions incorporated in AC during setting reaction may be one of the essential factors for CO3Ap formation.
Authors: Christophe Drouet, Christian Rey, Christèle Combes, Sophie Cazalbou, Stephanie Sarda, David Grossin
Abstract: This contribution gathers various examples illustrating the fact that nanocrystalline apatites represent a genuine multi-functionalizable platform for a wide range of biomedical applications. It is indeed possible to convey additional functionalities to the already appealing properties of biomimetic apatites, via appropriate ionic substitutions and/or through controlled molecular adsorptions. In link with bone regeneration, we depict here examples of enhanced osteoconduction/induction and of the addition of antibacterial features to bone implants. But we also point out the promise of apatite-based colloidal nanoparticles in other domains not related to bone, such as nanomedicine (cell diagnosis/therapy), which we address by conferring luminescence properties and by adding cell recognition abilities.
Authors: Nguyen Xuan Thanh Tram, Michito Maruta, Kanji Tsuru, Shigeki Matsuya, Kunio Ishikawa
Abstract: We have established a processing method to fabricate three - dimensional porous carbonate apatite (CO3Ap) with interconnected porous structure and improved mechanical strength. Briefly, porous CO3Ap materials were produced via phosphorization of porous calcite precursor in hydrothermal condition. In order to make porous calcite precursor, negative replication of modified polyurethane foam template was conducted. In this study, an in vivo behavior of that porous CO3Ap was evaluated. The interconnected porous CO3Ap material was implanted in the tibia of Japanese male rabbits and removed after a period of 6 months. Micro-computed tomography (μ-CT) scanner and histological analysis were used to characterize the bone formation response of the porous CO3Ap. The results suggest that porous CO3Ap with enhanced mechanical strength was not only osteoconductive but also bioresorbable therefore it could be used as bone substitute material.
Authors: Khairul Anuar Shariff, Kanji Tsuru, Kunio Ishikawa
Abstract: Regulation of DCPD formation on β-TCP granules was achieved by exposing β-TCP granular with different concentration of acidic calcium phosphate solution. It was found that a higher amount of DCPD was formed when exposed β-TCP granular with the higher concentration of acidic calcium phosphate solution. Morphological observation shows that the surface of β-TCP granular was fully coated with DCPD crystals after exposed with the higher concentration of acidic calcium phosphate solution. These results demonstrated that the DCPD formation on the β-TCP granular surface could be regulated by varying the concentration of acidic calcium phosphate solution.
Authors: Tai Joo Chung, Kyung Sik Oh
Abstract: The cause of the degradation was analyzed by applying the highly humid conditions during the storage of cement composed of β-tricalcium phosphate (β-TCP) and monocalcium phosphate monohydrate (MCPM). For the β-TCP and MCPM stored separately under the humid environment, the mild increase in the setting time was observed, and the product after the setting was entirely dicalcium phosphate dihydrate (CaHPO42H2O: DCPD). However, for the β-TCP and MCPM stored mixed under the same condition, the setting time significantly increased with the period of storage, and the product contained dicalcium phosphate (CaHPO4: DCP) as major phase, resulting in the loss of setting ability. The formation of DCP could be because of the weak driving force for setting, caused by a feeble supply of water from moisture. As the formation of DCPD requires stronger driving force to overcome the activation barrier, sufficient amount of water is essential. Humid environment during the storage decreased the driving force by the formation of DCP, and the driving force to produce DCPD was lost during the actual setting.
Authors: Innocent J. Macha, David Grossin, Besim Ben-Nissan
Abstract: Marine structure, coralline materials were converted to calcium phosphate using two different phosphate solutions. The aim was to study the conversion mechanisms under acidic and basic environment at moderate conditions of temperature. Crystal growth and morphology of converted corals were characterized by XRD and SEM respectively. The results suggested that under acidic conditions (H3PO4), dissolution and precipitation control and direct the crystal formation and morphology in which transition from plate like to rod like hydroxyapatite structure was favoured. Metastable phase such as monetite formed and transformed to HAp during reaction. During the first hour of the dissolution a monetite and hydroxyapatite mixture precipitates and then the full conversion to hydroxyapatite is observed. On the other hand, under basic conditions (NH4)2HPO4, just diffusional surface conversion of the calcium carbonate structure of coralline materials to hydroxyapatite and a very small amount of tri-calcium phosphate is observed. The mechanism can be classified as the solid-state topotactic ion-exchange reaction mechanism.
Authors: Hiroto Mizutani, Takeshi Yabutsuka, Shigeomi Takai, Takeshi Yao
Abstract: When the pH or the temperature of a simulated body fluid (SBF) is raised, fine particles of calcium phosphate are precipitated. We found that this particle actively induces apatite formation in body fluid or SBF and named it Apatite Nucleus (AN). In this study, we fabricated bone-like apatite self-supporting thin film by biomimetic method using AN. We analyzed it by FE-SEM, EDX, TF-XRD and ICP. It was found that the film has similar crystallinity and Ca/P ratio to those of biological apatite and ca. 10 μm of thickness.
Authors: Ahmet Talat Inan, Oguzhan Gunduz, Yesim Muge Sahin, Nazmi Ekren, S. Salman, Joshua Chou, Besim Ben-Nissan, Hasan Gökçe, Faik Nüzhet Oktar
Abstract: Calcium phosphates are very important biomaterials for orthopaedic and dental applications. Hydroxyapatite (HA) is one of the important phases used for grafting. Those are produced from synthetic and natural sources with various methods. Especially nano-bioceramics can be produced through calcitic and aragonitic structures (i.e. mussel shells, sea snail shells, land snail shells and sea urchin shells). The plate limpet shells were used. The plate limpet is a gastropod, a soft-bodied invertebrate (an animal without a backbone) that is protected by a very hard, flattened conical shell. In this study the Plate Limpet (Tectura scutum) shells were obtained from a local gift store in Istanbul. The habitation of these limpets broadens from south Alaska down to California - Mexico. First the exact CaCO3 content was measured with thermal analysis (DTA/TGA). Here in this study agitation was carried out on a hot-plate (i.e. mechano-chemical processing). First the temperature was set at 80 °C for 15 min. Then equivalent amount to CaO H3PO4 was added dropwise for HA phase formation and the reaction was set on a hotplate for 8 hours. The dried sediments HA part was divided into 2 groups. One group was sintered to 835 °C and second group to 855 °C. Here x-ray diffraction and scanning electron microscope (SEM) studies were performed. From the study various HA phases and TCP phases were obtained. A previous study done with Atlantic Deer Cowrie encourages nanobioceramic production from natural sources. This study proposes that mechanochemical agitation with very simple way for producing nano-sized calcium phosphates for future bioengineering scaffold applications.

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