Papers by Author: Tetsuya Kameyama

Abstract: MC3T3-E1 mouse osteoblast-like cells were seeded at high cell density to form confluent monolayer on rough surfaced culture substrates. Osteoblastic gene and protein expressions and matrix mineralization were investigated to clarify the effect of surface roughness on differentiation of MC3T3-E1 cells.

Abstract: The protein adsorption behavior was investigated for highly (001) oriented hydroxypatatite coatings (HACs). Highly (001) oriented (HO-) HACs and HAC with low orientation (LO-HAC) were prepared on titanium (Ti) substrates through a radio-frequency thermal plasma spraying method. Sintered HA pellets (S-HA) was also prepared as a control. The solution of 22 'g/100 'l PBS of the fluorescein-isothiocyanate (FITC) labeled bovine serum albumin (FITC-BSA), immunoglobulin G (FITC-IgG) and cytochrom c (FITC-CCC) was separately dropped on the surface of HACs and was incubated for 30 min. After the incubation, such HACs were washed with the PBS additionally supplemented with 125mM NaCl and observed using a fluorescence microscope. Fluorescence microscopic examination indicates that FITC labeled proteins somewhat adsorbed on the HACs, while proteins adsorbed little on S-HA surface. In particular, it can be seen that FITC-CCC adsorbed more prominently on the HO-HAC.

Abstract: There is a clinical need for synthetic scaffolds that will promote bone regeneration. Important factors include obtaining an optimal porosity and size of interconnecting macropores whilst maintaining scaffold mechanical strength, enabling complete penetration of cells and nutrients throughout the scaffold, preventing the formation of necrotic tissue in the centre of the scaffold. To address this we investigated flexural strength of bimodal porous apatite ceramics prepared using apatite slurry and its slurry synthesis was studied. Slips with different contents of HAp (K-HAp and T-HAp) and deflocculant were prepared by milling in a pot mill. The viscosity of slurries made of commercial T-HAp powder showed a drop after 3 hours’ milling, but the viscosity of slurry with high solid content of k-HAp and 2.0 wt% deflocculant increased with an increase of milling time after 2 hours’ milling. The porosity and flexural strength of the porous HAp prepared by heating the foam dipped in K-HAp slip with 2.0 wt% of deflocculant and 0.5wt% of foaming regent heated at 1200°C were 62.4 % and 14.7 MPa, and those in T-HAp were 59.7 % and 15.2 MPa with 1.5 wt% of deflocculant and 0.5wt% of foaming regent heated at 1200°C.

Abstract: Biphasic calcium phosphate (BCP) ceramics, a mixture of hydroxyapatite (HAp) and betatricalcium phosphate (β-TCP), of varying HAp/β-TCP ratios was prepared. One kinds of HAp and one kind of β-TCP powders were used to produce porous BCP bioceramics with HAp/β-TCP weight rations of 20/80, 40/60, and 80/20. A slip was obtained by adding a mixed powders of HAp and β-TCP to a solution 1.5% of deflocculant and 0.5 wt% of foaming agent. The optimum value for the minimum viscosity in these present slips with respect to its solid loading and the optimum amount of the deflocculant were investigated. The specimen obtained by casting a polyurethane foam with 1.5 wt% of deflocculant into a slip, and drying it under vacuum, was heated at 1150°C for 3 hours. The resultant porous BCP sintered body had large spherical pores of 300 /m with interconnecting rectangular voids. Many small pores in the size range of 2-3 /m or below were observed in the specimen obtained by heating at 1150°C for 3 hours. The dissolution test was done as follows. The obtained porous ceramics samples about 0.5g individually soaked into 30 mL of simulated body fluid (SBF) solution at 36.5°C. The calcium and phosphorous content of the SBF solution was analyzed by ICP. The porous body was dried, and characterized using SEM, XRD, and FT-IR.

Abstract: Preparation of apatite ceramics with bimodal pore structure was studied. First fine hydroxyapatite powder was obtained through mechanochemical method. The particle size of the product was around 0.64 µm. The slurry with the fine apatite powder content of 55-62.5wt% was prepared using defloculant, and foaming reagent. The organic form was immersed into the slurry, dried under vacuum, and heated at 1100°C, 1200°C, 1300°C. Pore size distribution of the product measured by porosimeter showed that small pores of around 1 µm and large pores of 100 µm exist, and SEM observation confirmed. SEM observation showed that the large pores seemed to be interconnected through the openings of several dozens µm in size. The porosity of the products were found to be 48 – 58.5%, and the bending strength of the products obtained by heat-treatment at 1100°C for 3 hours was 5.6 MPa, and that at 1200°C was 10.5 MPa.

Abstract: Biphasic calcium phosphate (BCP) ceramics, a mixture of hydroxyapatite (HAp) and beta-tricalcium phosphate (β-TCP), of varying HAp/β-TCP ratios were prepared from fine powders. Porous BCP ceramic materials with HAp/β-TCP weight rations of 20/80, 40/60, and 80/20 were prepared. In this study, the bioactivity is reduced at a larger HAp content rate, which is likely related to the high driving pore for the formation of a new phase, and the reaction rate was proportional to the β-TCP. The porous BCP ceramics having a bigger porosity rate can easily under up dissolution. The powder having a larger β-TCP content rate can easily generate a new phase. The dissolution results confirmed that the biodegradation of calcium phosphate ceramics could be controlled by simply adjusting the amount of HAp or β-TCP in the ceramics and porosity rate.

Abstract: A bimodal porous hydroxyapatite (HAp) body with high flexural strength was prepared through slip casting. HAp fine powder used in this study was synthesized by wet milling, drying and heating of a mixture of calcium hydrogen phosphate di-hydrate and calcium carbonate. The synthesized HAp powder was 0.32
0.05 μm in size and 38.1
0.8m2/g in specific surface area. The slip was prepared by adding deflocculant and foaming reagent. The optimum value for the minimum viscosity in the present HAp slip with respect to its solid loading and the optimum amount of the deflocculant were studied. The total porosity of the specimens obtained from a slip of 48 wt% HAp solid loading is in the range of 49 – 61vol %, and the resultant porous HAp sintered body had large spherical pores of 300 -m with interconnecting rectangular voids. Many small pores in the size range of 2-3 -m or below were observed in the specimen obtained by heating at 1100, and 1200 . The flexural strength of the bimodal porous HAp ceramics sintered at 1200 C showed a large value of 17.6 MPa, with a porosity of 60.5vol.

Abstract: Highly oriented hydroxyapatite (HA) coatings were prepared on titanium (Ti) substrates through a radio-frequency thermal plasma spraying method. XRD patterns showed that the HA coating layer had an structure with (00l) preferred crystal orientation. TEM observation showed that 200-800 nm-width prismatic crystals were formed in HA splats and the longitudinal axis of such prismatic crystals oriented vertical to the coating's surface. TEM images also indicate that the interface between prismatic crystals became compacted. SAD pattern show that the longitudinal axis of prismatic crystals corresponds to the <001> axis of HA.

Abstract: Two kinds of tri-calcium phosphate ceramics, β-TCP, which have the same macrostructure and microstructure, but different special surface area and particle size, were used in porous ceramics. A slip was obtained by adding the powders to a solution 1.0 wt% of deflocculant, respectively. The specimen obtained by casting a polyurethane foam with 0.5wt% into a slip, and drying it under vacuum, was heated at 1150
, for 3 hours. The porous ceramics samples about 0.5g were individually soaked into 30 mL of phosphate buffer saline (PBS) at 20
for 1,3,7 and 10 days, respectively. The calcium content of the PBS solution was analyzed by (ICP). The porous bodies were filtered, dried, and characterized using SEM, XPD, and FT-IR.

Abstract: Biphasic calcium phosphate (BCP) ceramics, a mixture of hydroxyapatite (HAp) and beta-tricalcium phosphate (β-TCP), of varying HAp/β-TCP ratios were prepared from fine powders. Porous BCP ceramic materials with HAp/β-TCP weight rations of 20/80, 40/60, and 80/20 were prepared. In this study, the bioactivity is reduced at a bigger HAp content rate, which is likely related to the high driving pore for the formation of a new phase, and the reaction rate was proportional to the β-TCP. The porous BCP ceramics having a bigger porosity rate can easily under up dissolution. The powder having a bigger β-TCP content rate can easily generate a new phase. The dissolution results confirmed that the biodegradation of calcium phosphate ceramics could be controlled by simply adjusting the amount of HAp or β-TCP in the ceramics and porosity rate.