|1.Research Institution||@||Sophia University|
|2.Research Area||@||Physical and Engineering Sciences|
|3.Research Field||@||Next-generation Process Technologies|
|4.Term of Project||@||FY 1997 ` FY 2001|
|6.Title of Project||@||Development of Process for Fabrications of Multi-functional Composites|
|Name||Institution,Department||Title of Position|
|Akira NOZUE||Sophia University, Faculty of Science and Technology||Professor|
|Names||Institution,Department||Title of Position|
|Hiroshi SUEMASU||Sophia University, Faculty of Science and Technology||Professor|
|Kiyoshi ITATANI||Sophia University, Faculty of Science and Technology||Associate Professor|
|Mamoru AIZAWA||Sophia University, Faculty of Science and Technology||Research Associate|
9.Summary of Research Results
The present project is aimed at the fabrications of high loading parts (hip joints) and low loading parts (substitute
materials for bones). Among the present subjects listed below, Subjects (1), (2), and (3) include the fabrication of
biocompatible and high loading parts, whereas Subjects (4) and (5) include the fabrication of low loading parts:
(1) Coating on the surfaces of high strength substrate by spray hydrolysis
Precursors of the calcium phosphate films were deposited on the substrate, e.g., alumina (Al2O3) and tetragonal zirconia (ZrO2), by spray-pyrolysing (i) solution (CA/P=0.50) for the adhesion for 5 h, and then (ii) solution (Ca/P=3.0) for film formation for 10 h. The substrate coated with precursors was heated at 1000 to 1300 for 5h in a steam atmosphere or air to form hydroxyapatite (Ca10(PO4)6(OH)2; HAp) films. The pore-size distributions were in the range of < 1Êm, 1-100Êm, and 100-200Êm. The results on the cell proliferation and differentiation using osteoblastic cell (MC3T3-E1) showed that the HAp-coated material had good biocompatibility, as compared with the control and the substrates without coating.
(2) Coating on the titanium substrates by soft solution technique
The HAp coating was conducted by immersing the Ti-6Al-4V substrate (diameter of 14 mm and thickness of 1.5mm) heated at 200 into (i) the simulated body fluid (5cm3), (ii) the simulated body fluid and 1 molEdm3 urea (5cm3), and (iii) the simulated body fluid, urea, and urease (0.03cm3). The immersed substrate allowed to stand in an incubator (37 or 50) and replaced with the simulated body fluid. Larger amount of HAp was formed on the surfaces of Ti-6Al-4V substrate with increasing concentration of simulated body fluid and heat-treatment temperature. The results on the cell proliferation and differentiation using osteoblastic cell (MC3T3-E1) showed that the HAp-coated material had good biocompatibility, as compared with the control and the substrates without coating.
(3) Formation process of self-restoration function
Surfaces of the Ti-6Al-4V specimen with sizes of 35~34~4-8mm3 and crack length of 17mm were modified using alkali-treatment technique, i.e., (i) the treatment of 5 mol¥dm3 NaOH at 60 for 24h, (ii) drying at 37 for 24h, and then (iii) immersion into the simulated body fluid at 37 for three weeks. The HAp was precipitated not only on the surfaces but also on the introduced cracks of Ti-6Al-4V specimen. When HAp was precipitated on the Ti-6Al-4V specimen by utilizing the NaOH treatment, the fracture toughness increased from 60MPaEm1/2 to around 72MPaEm1/2 after 1500h of immersion.
(4) Process of bone-like composites and evaluation
The hybrid materials, i.e., HAp-poly (methylmethacrylate) (PMMA), were fabricated as follows: (i) the introduction of MMA monomer containing the azobis(isobutyronitrile) (AIBN) as a polymerization initiator into the porous HAp ceramics, and (ii) the bulk polymerization of the introduced MMA monomer by heating at 60 for 48 h. The porous HAp ceramics with controlled porosities were fabricated using fibrous HAp with long-axis sizes of 50-100Êm. Mechanical properties of the hybrid materials were as follows: Young's modulus, `63GPa; fracture toughness, `2MPaEm1/2 and; flexural strength, `65MPa. The present hybrid materials proved to have a good biocompatibility close to the HAp ceramics.
(5) Fabrication of HAp-Collagen Composites
The porous HAp ceramics with average pore sizes of 90Êm, 200Êm, and 300Êm were immersed into the solutions with the collagen contents of 1 to 4.8 mgEcm-3 and were freeze-dried for 24h. The heat-treated materials at 100-150 were immersed into the ethanol and, furthermore, were freeze-dried to obtain the composites. The amount of collagen was the largest when the average pore size and collagen content in the solution were 300Êm and 4.8 mgEcm-3, respectively. The amount of collagen increased linearly with increasing number of operation and exceeded 10% after 20 times. SEM micrographs revealed that the membrane-like collagen was present in the continuous pores and that the pores were present not only on the surfaces but also inside pores.
(4)Bone-like composite ProcessingA(5)High Loading PartsA(6)Low-Loading Parts
(7)BiocompatibilityA(8)In vitro ExaminationA(9)In vivo Examination