Bioceramics 24

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Authors: Junichi Tazaki, S. Yodogawa, Masaru Murata, K. Ito, T. Akazawa, J. Hino, Md.A. Kabir, H. Nagayasu, M. Arisue, T. Shibata, T. Hanawa
Abstract: Our approach to the design of biological material scaffolds for bone regeneration is the creation of cell environments that mimic natural tissues. Recently, we confirmed hitologically that the material surfaces of conventional, nonabsorbable ceramics shed body fluid. For bone engineering, it is known that ideal scaffolds should be bioabsorbable, mimetic, and hydrophilic materials that allow for the permeation of liquid components, such as blood and/or extracellular fluid. In our previous study showed functionally graded hydroxyapatite (fg-HAp) absorbed body fluid including albumin. In this study, we investigated the behavior of human blood adsorption to the fg-HAp by using the scanning electron microscope (SEM). The adsorption of the platelets and the formation of the fibrinous network were observed in the fg-HAp group incubated 20 minutes.
Authors: Junichi Tazaki, Masaru Murata, Toshiyuki Akazawa, M. Yamamoto, K. Ito, J. Hino, Y. Minamida, H. Nagayasu, M. Arisue, T. Shibata, Y. Tabata
Abstract: We previously reported functionally graded hydroxyapatite (fg-HAp) with the characteristics of blood permeability into the bulk and osteoinduction by adding low dose of bone morphogenetic protein-2 (BMP-2). In this study, we evaluated the bioactivity of the obtained dense HAp bodies in a simulated body fluid (SBF) and the osteoinductive activity with or without SBF treatment in vivo. The fg-HApSBF was prepared by immersing the fg-HAp in the SBF solution at 14 days and the surface structure was observed by SEM. The fg-HApSBF showed fine bone-like crystal on the surface of the HAp. Ectopic bone formation occurred in the fg-HAp/BMP-2 (1.0, 0.5μg) system at 3 weeks, while only in the fg-HApSBF/BMP-2 (1.0μg), bone induction was found. The histological finding showed body fluid permeation into the fg-HApSBF bulk and bone formation were obserbed.
Authors: Ryo Hamai, Takeshi Toshima, Masamoto Tafu, Takaaki Masutani, Tetsuji Chohji
Abstract: Brushite (DCPD, CaHPO4·2H2O) crystals are of great significance in a range of fields including biology, medicine, chemistry, and materials science. One important issue is the control of their morphology; when the crystal growth conditions are changed, the morphology and surface crystal conditions also change. The chemical reaction behavior depends strongly on the surface condition of the particles. Here, we report the effect of coexisting anions on the morphology control of DCPD particles. We synthesized the particles through a liquid-phase reaction by mixing a starting solution of ammonium dihydrogen phosphate (NH4H2PO4) and calcium salts. Calcium nitrate (Ca (NO3)2) and calcium acetate (Ca (CH3COO)2) were used as the calcium sources to clarify the pH dependence of the morphology. We mixed the solutions with the same pH values and agitated them, and observed the products by scanning electron microscopy (SEM) and X-ray diffraction (XRD); the DCPD morphology varies from petal-like to parallelogram structures depending on the initial pH value of the solution and the combination of the starting mixture. The effect of the acetic acid anion is to increase the driving force for the generation of DCPD crystal nuclei.
Authors: Hideki Shimizu, Zhi Zhuang, Mamoru Aizawa
Abstract: We focused on the investigation of the influence of carboxylic acid additives on the morphology of hydroxyapatite (Ca10(PO4)6(OH)2, HAp) particles synthesized by a homogeneous precipitation method. Three types of carboxylic acids with different number of carboxyl groups, that is, acetic acid, succinic acid and citric acid, were used as additives to control the nucleation, growth and alignment of HAp crystals. The powder properties of resulting particles were examined by powder X-ray diffractometry, fourier-transform infrared spectroscopy, and scanning electron microscopy. All resulting particles were identified to be single-phase carbonate-containing calcium-deficient HAp. The resulting particles synthesized by using acetic acid as an additive were strip-like morphology. In the case of succinic acid addition, the resulting particles exhibited irregular plate-like or spherical morphology. Wheileas, in the case of citric acid addition, the obtained particles became regular spherical shape. These results indicate the numbers of carboxyl groups of carboxylic acid give an influence of the morphology of the HAp particles.
Authors: Jung Sang Cho, Sang Hoon Rhee
Abstract: The size of hydroxyapatite particles during spray pyrolysis was successfully controlled by varying the concentrations of the starting calcium phosphate (CaP) solutions. Three different concentrations of CaP solutions were prepared by dissolving Ca (NO3)4H2O and (NH4)2HPO4 into deionized water and then they were sprayed at 900°C with the carrier gas flowing rate of 10 L/min. The size of the resultant hydroxyapatite particles decreased as lowering the concentration of the starting CaP solution. The smaller the particle size, the higher the relative density of the hydroxyapatite disks after sintering at 1100°C for 1 hour. The practical implication of the results is that highly sinterable hydroxyapatite particles can be synthesized during spray pyrolysis by controlling the starting concentration of CaP solution.
Authors: Satoshi Hayakawa, Yuki Shirosaki, Akiyoshi Osaka, Christian Jäger
Abstract: Hydroxyapatite (HAp) particles were synthesized by solid-state reaction and wet chemical reaction, and were characterized in terms of their chemical composition, disordered structure and in vitro biodegradability. An X-ray diffraction study revealed that the prepared HAp particles were composed of single phase HAp, while 1D and 2D solid-state NMR analysis showed that they consisted of not only crystalline HAp but also a disordered phase. An in vitro biodegradability test showed that wet chemically derived HAp particles were degraded quicker than commercially available HAP-100. The in vitro biodegradability was discussed by using a structure model for nanocrystalline HAp, in which the nanocrystals consist of a crystalline HAp core covered with a disordered surface layer (core-shell model). Although the specific surface area was the predominant factor on the rate of Ca ion dissolution, the disordered surface layer enhanced the release of Ca ions in the initial stage within 1 min, while the crystalline core of HAp also gave different release rate of Ca ions, depending on the chemical distribution in the P (V) environment.
Authors: Tomohiko Yoshioka, Hiroshi Yonekura, Toshiyuki Ikoma, Motohiro Tagaya, M. Tanaka
Abstract: This study is concerned with multilayered protein adsorption on carbonate apatite (CAp) that is measured with a quartz crystal microbalance (QCM) technique. A carbonate apatite-deposited QCM sensor was prepared by electrophoretic deposition (EPD). On the CAp-deposited QCM sensor, fibrinogen adsorption followed by thrombin adsorption was investigated. The adsorption of fibrinogen on CAp led to a clear decrease in the resonance frequency of the sensor, which means that fibrinogen adsorbed on the CAp-deposited QCM sensor. The adsorbed amount of fibrinogen was larger on CAp than on a pristine sensor (Au). Although successive thrombin adsorption occurred on fibrinogen adlayers on both CAp and Au, the adsorbed amount and its conformation were different depending on the surface.
Authors: Shunsuke Nomura, Kanji Tsuru, Shigeki Matsuya, Ichiro Takahashi, Ishikawa Kunio
Abstract: We fabricated spherical carbonate apatite from spherical calcium sulfate which was prepared by w/o emulsion method. Calcium sulfate hemihydrate slurry was dropped in oil under continuous stirring and was kept at room temperature for 60 min to obtain set spherical calcium sulfate dihydrate (CaSO42H2O) with approximately 1 mm in diameter. The spherical CaSO42H2O was hydrothermally-treated at 120°C for 24 hours in the presence of 0.4 mol.L-1 disodium hydrogen phosphate and sodium hydrogen carbonate aqueous solution. X-ray diffraction patterns assigned to apatite single phase could be detected from the obtained spheres. Carbonate content in apatitic structure was found to be approximately 6.5wt%.
Authors: Seiko Ohba, Wei Wang, Soichiro Itoh, Akiko Nagai, Kimihiro Yamashita
Abstract: The effects of electrically polarized HA microgranule/PRP compositeon new bone formation were examined. The composite gel was implanted into bone holes in rabbits. Histological examination was performed 3 and 6 weeks post-surgery. It was hypothesized that PRP alone could not induce new bone formation until 6 weeks after implantation. HA microgranules with or without electrical polarization/PRP composite, especially the former, activated osteogenic cells, resulting in enhanced bone formation. It was confirmed that electrical polarization treatment of HA microgranules can accelerate new bone formation and this effect is enhanced by forming a complex within PRP.
Authors: Flora E. Imrie, Valentina Aina, Gigliola Lusvardi, Gianluca Malavasi, Iain R. Gibson, Giuseppina Cerrato, Basil Annaz
Abstract: Magnesium and strontium both play important roles in the growth of bone and so are desirable ions for substitution into hydroxyapatite (HA) intended for use as bioinstructive bone substitutes. A range of compositions were prepared by a solid state method based on the nominal composition of HA (Ca10(PO4)6(OH)2), with various levels of strontium and/or magnesium substitution: strontium-substituted HA (Ca8Sr2(PO4)6(OH)2), magnesium-substituted HA (Ca9.8Mg0.2(PO4)6(OH)2 and Ca9Mg (PO4)6(OH)2), and strontium and magnesium co-substituted HA (Ca7.8Sr2Mg0.2(PO4)6(OH)2 and Ca7Sr2Mg (PO4)6(OH)2). Materials were characterised by powder X-ray diffraction, Fourier-transform infrared spectroscopy and Raman spectroscopy. These analyses indicated that the co-substituted materials were composed of mixtures of strontium-substituted hydroxyapatite and magnesium and strontium co-substituted β-tricalcium phosphate. In the magnesium-substituted materials, increased magnesium content was related to increased proportion of β-tricalcium phosphate phase, both with and without strontium co-substitution. The unsubstituted and strontium mono-substituted materials, however, were pure apatite phase, suggesting that magnesium was the destabilising factor in the phase compositions of the magnesium mono-substituted and magnesium and strontium co-substituted materials.

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