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This laboratory has conducted four research projects mainly in the field of bioceramics for the use of artificial bones, bioreactors and other clinical materials. The objects and outstanding results are described as follows.
The aim of this study is to develop in situ water treatment systems in rivers and lakes using recycled local materials to reduce pollution of the water supply. Waste ceramic materials have been considered potentially useful as recycling materials for preparation of porous carriers for supporting microbial adhesion and growth. Therefore, the effects of the surface structure of porous ceramics on adhesion of microorganisms and the biological purification abilities were investigated by using surface-modified ceramics.
Design and synthetic methods for porous ceramic carriers from recyclable waste materials were also investigated for enhancement of microbial functions. Residues of activated sludge in wastewater treatment were mixed with ceramic grains to prepare porous carriers. A sintered composite material, which had an ash-coated surface, showed high performance with respect to wastewater treatment.
These results suggest that the surface zeta potential is one of the dominant factors influencing the increase in adhesiveness of microbes to ceramics.
HAp has also been used as the material for column packings to separate and refine proteins and other polymers present in body fluids. HAp expresses different structures in the a and c planes and absorbs different types of proteins depending on the crystalline planes. It is thus expected that its selectivity characteristics with specific protein types can be controlled if its crystalline morphology can be controlled. HAp with controlled morphologies could have application in liquid chromatography column packings.
The effect of methanol on the morphology of HAp has been studied under hydrothermal conditions. The morphology of the products was influenced by the amount of methanol added to the starting materials. When the weight of methanol was equal to that of starting materials, the oriented HAp crystal with a-plane grew preferentially. The crystal would be applied to effective separation of biopolymers.
Reference
(2)F. Nagata et al., J. Ceram. Soc. Jpn.,(Int. Edition),103 , 69(1995).
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The number of people needing artificial bones and teeth will rapidly increase in the world. Hydroxyapatite(HAp) is known to be a suitable ceramic owing to its biological affinity. However, it is difficult to use it in artificial joints and dental roots due to its poor mechanical properties. A radio-frequency thermal plasma coating of HAp on mechanically strong materials has been tried. This process has proved to be promising from the viewpoint of preparing pure coatings. Recently, a new method to implant HAp granules into the surface of superplastic titanium-alloy was developed in our institute to obtain both biological affinitity and high mechanical strength. HAp granules (32-38mm diameter) were implanted on the surface of the alloy by pressing them at a pressure of 17MPa, 750°C for 10min. Tops of the granules were surrounded by the alloy, remained exposed and were firmly stuck in the substrate. The HAp-inplanted titanium-alloy hybrid materials are expected for use as hard biological tissues replacement.
References
(3)T. Kameyama et al., Proceedings of 14th Int. Thermal Spray Conf., 187(1995).
(4)T. Nonami et al., J. Mater. Sci. Mater. in Medicine, 9, 203(1998).
Recent biomimetic studies concerned with stimulation of calcium phoshate growth on substrates have become an extremely important part of biomaterials research due to the insights such investigations can provide on the natural deposition of bone-like materials in the body.
In this research project, we have succeeded in growing calcium phosphate on surface-modified polymers(cotton and chitin fibers). Fibers phosphorylated by the urea/H3PO4 or urea/H3PO4 soaked in saturated Ca(OH)2 for one week were found to stimulate the growth of a calcium phosphate coating on their surfaces after soaking in 1.5xSBF(Simulated Body Fluid) for as little as 1 day. Cotton/HAp system may be used as a virus filter and artificial trachea in the future.
References
(5)M. R. Mucalo et al., J. Mater. Sci. Mater. in Medicine,6, 658(1995).
(6)Y. Yokogawa et al., J. Mater. Sci. Mater. in Medicine, 8, 407(1997).
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