Papers by Author: Shigeki Matsuya

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.

Abstract: In this study, three - dimensional porous carbonate apatite (CO₃Ap) materials with the chemical compositions and structures similar to cancellous bone were produced via phosphorization of porous calcite precursor in hydrothermal condition. In order to make porous calcite precursor, negative replication of polyurethane foam that named as inverse ceramic foam method was conducted. When the polyurethane template occupied within the ceramic solid walls disappeared due to burning at high temperature, interconnected hollow pathways were produced. Polyurethane foam was used as a porogen - template firstly was coated layer by layer with synthetic resin to modify morphology and enlarge thickness of struts so as to expand porous area for satisficing cellular bioactivities. Calcium hydroxide (Ca(OH)₂) slurry was then infiltrated into resin coated-polyurethane foam. Heat treatment in atmosphere of oxygen and carbon dioxide gases was carried out to eliminate polyurethane template and induce carbonation process. Ca(OH)₂ was converted to calcite with the internal porous channel architecture simulating polyurethane foam struts network. That interconnected porous calcite was subsequently transformed to CO₃Ap with remaining the same macroporous structure through hydrothermal treatment in phosphate solution. The porous CO₃Ap materials were implanted in the tibia of Japanese male rabbits and removed after a period of 3 months. The bone formation response of the three - dimensional porous carbonate apatite in vivo has been preliminary studied using micro-computed tomography (µ-CT) scanner. The results showed that the porous implant materials have sufficient mechanical strength to provide structural support during bone remodeling and successfully bond with host bone.

Abstract: The present study reports the synthesis of carbonate apatite foam with fully interconnecting pores from βTCP foam by hydrothermal treatment in 1 mol·L^-1 disodium carbonate solution at 200°C. The βTCP foam were prepared; 1) using 3 mol% Mg as βTCP stabilizer, 2) using αTCP foam as a precursor by heat treatment at 900°C for 100 hours. The βTCP foam containing Mg could not transform to carbonate apatite foam completely. Meanwhile, the βTCP foam heat-treated at 900°C transformed to carbonate apatite after hydrothermal treatment for 10 days without morphological change. Compressive strength measurement indicated that the value of carbonate apatite foam derived from βTCP was significantly higher than that from αTCP.

Abstract: Zinclipscombite (ZnFe³⁺₂(PO₄)₂(OH)₂) coating layer was prepared on 316L SS. The 316L SS plates were treated using hydrothermal treatment at 200°C for 2, 6 and 24 h. The ZnFe³⁺₂(PO₄)₂(OH)₂ layer strongly attached to the 316L SS surface. The adhesive strength of the coating layer was measured higher than 65.7 ± 3 MPa. The surface observation and element analysis indicated that the 316L SS plates were covered with ZnFe³⁺₂(PO₄)₂(OH)₂ coating layer after hydrothermal treatment. Linear voltammograms for treated sample at 200°C for 24 h showed higher corrosion resistance. The ICP results proved protective property for the zinclipscombite coating agains PBS solution.

Abstract: This study aims to improve the handling property of alpha-tricalcium (αTCP) cement. In order to improve the handling property, the effect of γ-poly-glutamic acid (γPGA) as a chelating agent was studied. γPGA is water soluble, biodegradable, nontoxic, and edible material. γPGA contains carboxyl group, so the chelating effect between Ca²⁺ ions released from calcium phosphate cement and carboxyl group of γPGA is prospected when it mixed with αTCP based cement. The results obtained in this study clearly demonstrated that the addition of γPGA into the αTCP cement was highly effective in controlling the handling property of αTCP cement.

Abstract: Carbonate apatite showed an excellent bioresorbability through the remodeling process of bone. In the present study, we prepared self-setting carbonate apatite cement based on α-TCP. We tried two types of the cement powder formulations, that is, first one (F1) is α-TCP containing given amounts (10 to 50 mass%) of synthesized carbonate apatite and second one (F2) is α-TCP treated in 0.5M NaHCO₃ for various times between 90 and 360 min. The cement powder was mixed with 0.25M Na₂HPO₄ to allow set at 37°C and 100% of relative humidity up to 1 day. XRD and FT-IR results showed formation of B-type carbonate apatite phase after setting in both of the formulations. With the formulation, F1, the carbonate content was increased with the treatment time and the maximum content was 4.1 mass%. DTS deacreased with the amount of cabonate apatite in the formulation, F1, however, it increased up to 9 MPa with treatment time in the formulation, F2.

Abstract: The aim of the present study is to fabricate bone cement that could transform to carbonate apatite (CO₃Ap) completely at body temperature. The powder phase of vaterite and dicalcium phosphate anhydrous (DCPA) was mixed with 0.8 mol/L of NaH₂PO₄, Na₂HPO₄, and Na₃PO₄ aqueous solution, respectively, with liquid to powder ratio (L/P ratio) of 0.45, 0.55, and 0.65. The paste was packed into split stainless steel mold, covered with the glass slide and kept at 37°C and 100% relative humidity for up to 96 hours (h). XRD analysis revealed that the cement became pure CO₃Ap within 24 h for Na₃PO₄, 72 h for Na₂HPO₄, and 96 h for NaH₂PO₄, respectively. FT-IR results showed that all of the obtained specimens could be assigned to B-type CO₃Ap. CHN analysis showed the carbonate content of the specimen were 10.4 ± 0.3% for NaH₂PO₄, 11.3 ± 0.7% for Na₂HPO₄, and 11.8 ± 0.4% for Na₃PO₄, respectively. Diametral tensile strength of the set CO₃Ap cement was 1.95 ± 0.42 MPa for NaH₂PO₄, 2.53 ± 0.53 MPa for Na₂HPO₄, and 3.45 ± 1.53 MPa for Na₃PO₄, respectively. The set CO₃Ap cement had low crystallinity similar to bone apatite since it was synthesized at body temperature. We concluded, therefore, that CO₃Ap cement prepared from the present method has higher possibility to be used as an ideal bone replacement.

Abstract: The present study reports the synthesis of βTCP foam with fully interconnecting pores based on phase transformation of αTCP foam precursor by employing heat treatment. First, the αTCP foam precursor was fabricated by sintering the ceramics slurry-coated polyurethane foam template at 1,500°C. The resultant αTCP foam was again heated below α,β transition temperature for an extended period of times. After heating at 800°C for 150 hours, 900°C for 100 hours and 1,000°C for 300 hours, βTCP foam was obtained. The compressive strength of βTCP foam was approximately 46 kPa and the porosity was approximately 93%. The long heating period as well as heating temperature were the key to the transformation of βTCP phase. βTCP foam could be an ideal bone replacement since the invasion of bone cells into the pores provides optimum bone growth or repair.

Abstract: We have previously reported that calcite foam that had interconnected porous structure could be prepared by ceramic foam method and it transformed to carbonate apatite (CO₃Ap). In the ceramic foam method, polyurethane sponge was used as a template. The polyurethane sponge was immersed in the ceramics slurry, and the strut of the polyurethane foam was covered by ceramic powder. After that it was dried and sintered at high temperature. Calcite foams produced by this approach were comprised of a three-dimensional (3D) interconnected porous structure that facilitated cell penetration. However, all foams have a common limitation: the inherent lack of mechanical strength associated with high porosity. Therefore, in this study, an inverse ceramic foam method was studied; multi polyurethane coating method using polyurethane foam as a template. In this study, the compressive strength was improved by an inverse replication allowed for decreasing porosity while at the same time maintaining the interconnectivity. The burnable synthetic resin coating layer was introduced onto struts of polyurethane foam to make the triangular struts become more round and thick, consequently producing large round capillary within the foam structure fulfilling the requirement for osteoblast colonization. In particular, polyurethane foam was dipped orderly into two monomers, followed by centrifugation to remove excess liquids inside foam. After resin curing, a layer of synthetic resin was coated strut of foam. Calcium hydroxide Ca (OH)₂ slurry was then infiltrated into resin coated-polyurethane foam. By firing at 600°C in O₂-CO₂ stream, polyurethane template was burnt off and Ca (OH)₂ was converted into calcite. Negative replicated calcite foam was fabricated and characterized micro-structurally with interconnectivity and improved mechanical strength. The results obtained in this study suggested that this method dramatically improved the mechanical strength of the calcite foam without sacrificing the interconnected structure, and this means that the calcite foam obtained in this method could be precursors for the 3D interconnected porous CO₃Ap foam.

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%.