1989 Fiscal Year Final Research Report Summary
Epitaxial growth of amino acids on hydroxyapatite and bone formation mechanism
| Project/Area Number |
62470143
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
結晶学
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| Research Institution | Tokyo Medical and Dental University |
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Principal Investigator |
AKAO Masaru Tokyo Med. Dent. U., Div. Inorg. Mater. As. Prof., 医用器材研究所, 助教授 (50143607)
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| Co-Investigator(Kenkyū-buntansha) |
AOKI Hideki Tokyo Med. Dent. U., Div. Inorg. Mater. Prof., 医用器材研究所, 教授 (80014166)
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| Project Period (FY) |
1987 – 1989
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| Keywords | Hydrothermal synthesis / Hydroxyapatite / Carbonate group / Crystal structure / Hydroxyproline / Epitaxial growth / Tissue reaction / Bone formation |
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| Research Abstract |
Carbonate hydroxyapatite single crystals of length 5.5 mm were grown hydrothermally, which contained 1 wt% of CO_2, The crystal is hexagonal, space group P6^^- with a=9.471, c=6.891 A^^ﾟ and Z=I. The a-axis cell parameter is 0.6 % longer than that of hydroxyapatite. The structure is in principal the same as that of hydroxyapatite but the location of the OH groups differs from hydroxyapatite. The OH groups locate around the mirror planes at Z=1/2 but they are vacant at Z=O. Although the location of CO_3 groups was not found, the following two models were proposed. 1) CO_3 groups occupy the OH sites. 2) CO_3 groups occupy the vacant sites.
Affinity of hydroxyapatite with amino acids was characterized by estimating the crystallographic orientation relationships between hydroxyapatite and amino acid single crystal overgrown on the hydroxyapatite. For amino acids, 4-hydroxy-L-proline and L-serine were selected. The orientation relationships were determined with X-ray diffractometry and polarized microscopy and were discussed crystallographically. Hydroxy-L-proline was epitaxially grown on the hydroxyapatite single crystals. The epitaxial growth resulted in hydrogen bonding between hydroxy-L- proline and the hydroxyapatite surfaces.
Carbonate hydroxyapatite single crystals were implanted in the medullary cavity of Wister rats. After 1 week of implantation, new bone formation around the single crystals was observed together with absorption of cortical bone near the crystals. At 2 weeks, the newly formed bone around the crystals matured, however a part of the newly formed bone was absorbed. At 4 weeks, most of the newly formed bone disappeared and also a dissolution of the single crystals began. Thus the carbonate hydroxyapatite had ability of bone formation.
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