I-C. Kang et al./ Materials Letters 59(2005)69-73 cated to fabricate the homogenous pore structure, and the cultured in DMEM( Gibco demented with 10% heat pore size is only dependent on the size of the pore-forming inactivated fetal bovine serum(FBS, Gibco),2 mM L- glutamine, penicillin 100 U/ml, streptomycine 100 ug/ml, To date, fibrous monolithic process was introduced to fungizone 0. 25 ug/ml(Bio-Whittaker)and were placed in an fabricate a toughened and fibrous monolithic ceramic body incubator containing 5% CO2 at 300 K. After confluence, and proved to be convenient for controlling the micro- the cells were detached with 0.05% trypsin and 0.02% structure [13-15]. It is defined as a repeated extrusion of EDTA (Sigma). A 100 ul of 5x 10" cells were seeded on the two or more ceramic powders combined by organic binders top surface of second and third passed Al2O3 porous bod according to the principle that the area of each extruded bar (2-mm diameter and 1-mm height)in 96-well plate. After 5 is homogeneously reduced with the extrusion ratio. How h, these porous bodies adhered cells were cultured in new ever, the research on the fabrication of porous Al2O3 body 24-well plates and were observed for 2 week has not yet been conducted by using the fibrous monolithic The microstructure and composition of the filaments was kamined using a Field Emission Scanning Electron Micro- In this work, the bioinert Al2O, body consisting of the scope(FE-SEM, JSM 6335F)and Energy Dispersed Spec ontinuous pores was fabricated using fibrous monolithic troscopy(EDS, Oxford 400), respectively. The structure of process, and porous microstructure was examined. Behavior the resultant phases was characterized by an X-ray diffrac- of osteoblast adhesion and growth using human osteoblast- tometer(Rigaku, AX-2500)using Cu Ko of 0. 1542 nm like MG-63 cells on the fibrous monolithic Al2O3 porous body was also examined 2. Experimental procedure Fig. 1 shows SEM micrographs of AlO3/EVA and carbon/EVA composites with passes of extrusion. The first eth Homogenous mixtures of commercially used Al203/ passed filament consists of the carbon rod of about 2.3 mm lylene vinyl acetate(EVA)and carbon/EVA were prepared in diameter and Al2O shell of about 0.6 mm in thickness using a heated blender (C.w. Brabender Instruments, (Fig. 1(a)). After the second extrusion, both the rod (dark PL2000 Plasti-Corder with Roller Blade Mixing Heads ). color) and shell (light color) become fine to be approx The average diameter of starting materials was about 0.3 um imately 250-300 and 100 um, respectively, as shown in Fig for Al2O3(AKP-50, Sumimoto, Japan)and -10-15 um for 1(b). The third passed bar showed a further refinement in the carbon powder(SMC, South Korea). The EVA, a type of microstructure, thus it is impossible to distinguish the polymer, used for the binder in the shape of granules(Elvax microstructural distribution under the same magnification 250, Dupont) was composed of ethylene vinyl acetate (Fig. 1(c). The highly magnified micrograph taken from P (EVA). Stearic acid(CH3(CH2)16COOH(Daejung Chem- region in Fig. 1(c)indicates that the third passed filament icals metals, South Korea) was also added for lubrication during blending. The ratio of each constituent in the mixture was 50/45/5 vol. for the Al,O3/EVA/lubricant and 55/40/5 vol. for the carbon powder/EVA/lubricant. 器冷 order to blend both the Al2O3 and pore materials with the EVA, the eva granules were first put into the mixing 你毒品 chamber and head which were heated to 403-433 K using an oil-type heating source. Then, the Al2O3 powder and the 已命 pore materials were slowly added to the chamber having the heated head revolving at 60 rpm. The two mixtures of Al2O3/EVA and carbon/EVA were, respectively, extruded at 383 K into a filament of 3.5 mm in diameter with an extrusion ratio of 73: 1. Then, both the Al,O3 and carbon filament were reloaded in the extrusion die as densely as possible followed by reextrusion. This process was con- tinued until the third passed filaments were obtained. Binder urning out(BBO)of the filaments was carried out at 973 K under flowing nitrogen and then 773 K under air followed 点 by sintering at 1723 K. Human osteoblast-like MG-63 cells obtained from Korean Cell Line Bank(KCLB) were used to investigate Fig. 1 SEM micrographs of fibrous monolithic(Al2O3-CyEVA composite the adherence and the morphological changes of cells on the filaments with passes of extrusion. a-first, b--second, c--third pass, and fibrous monolithic Al2O3 porous body. The cells were d-enlarged image of the third passcated to fabricate the homogenous pore structure, and the pore size is only dependent on the size of the pore-forming agent. To date, fibrous monolithic process was introduced to fabricate a toughened and fibrous monolithic ceramic body and proved to be convenient for controlling the micro￾structure [13–15]. It is defined as a repeated extrusion of two or more ceramic powders combined by organic binders according to the principle that the area of each extruded bar is homogeneously reduced with the extrusion ratio. How￾ever, the research on the fabrication of porous Al2O3 body has not yet been conducted by using the fibrous monolithic process. In this work, the bioinert Al2O3 body consisting of the continuous pores was fabricated using fibrous monolithic process, and porous microstructure was examined. Behavior of osteoblast adhesion and growth using human osteoblast￾like MG-63 cells on the fibrous monolithic Al2O3 porous body was also examined. 2. Experimental procedure Homogenous mixtures of commercially used Al2O3/ ethylene vinyl acetate (EVA) and carbon/EVA were prepared using a heated blender (C.W. Brabender Instruments, PL2000 Plasti-Corder with Roller Blade Mixing Heads). The average diameter of starting materials was about 0.3 Am for Al2O3 (AKP-50, Sumimoto, Japan) and ~10–15 Am for carbon powder (SMC, South Korea). The EVA, a type of polymer, used for the binder in the shape of granules (Elvax 250, Dupont) was composed of ethylene vinyl acetate (EVA). Stearic acid (CH3(CH2)16COOH (Daejung Chem￾icals & Metals, South Korea) was also added for lubrication during blending. The ratio of each constituent in the mixture was 50/45/5 vol.% for the Al2O3/EVA/lubricant and 55/40/5 vol.% for the carbon powder/EVA/lubricant. In order to blend both the Al2O3 and pore materials with the EVA, the EVA granules were first put into the mixing chamber and head which were heated to 403–433 K using an oil-type heating source. Then, the Al2O3 powder and the pore materials were slowly added to the chamber having the heated head revolving at 60 rpm. The two mixtures of Al2O3/EVA and carbon/EVA were, respectively, extruded at 383 K into a filament of 3.5 mm in diameter with an extrusion ratio of 73:1. Then, both the Al2O3 and carbon filament were reloaded in the extrusion die as densely as possible followed by reextrusion. This process was con￾tinued until the third passed filaments were obtained. Binder burning out (BBO) of the filaments was carried out at 973 K under flowing nitrogen and then 773 K under air followed by sintering at 1723 K. Human osteoblast-like MG-63 cells obtained from Korean Cell Line Bank (KCLB) were used to investigate the adherence and the morphological changes of cells on the fibrous monolithic Al2O3 porous body. The cells were cultured in DMEM (Gibco) supplemented with 10% heat inactivated fetal bovine serum (FBS, Gibco), 2 mM l￾glutamine, penicillin 100 U/ml, streptomycine 100 Ag/ml, fungizone 0.25 Ag/ml (Bio-Whittaker) and were placed in an incubator containing 5% CO2 at 300 K. After confluence, the cells were detached with 0.05% trypsin and 0.02% EDTA (Sigma). A 100 Al of 5
104 cells were seeded on the top surface of second and third passed Al2O3 porous body (2-mm diameter and 1-mm height) in 96-well plate. After 5 h, these porous bodies adhered cells were cultured in new 24-well plates and were observed for 2 weeks. The microstructure and composition of the filaments was examined using a Field Emission Scanning Electron Micro￾scope (FE-SEM, JSM 6335F) and Energy Dispersed Spec￾troscopy (EDS, Oxford 400), respectively. The structure of the resultant phases was characterized by an X-ray diffrac￾tometer (Rigaku, AX-2500) using Cu Ka of 0.1542 nm. 3. Results Fig. 1 shows SEM micrographs of Al2O3/EVA and carbon/EVA composites with passes of extrusion. The first passed filament consists of the carbon rod of about 2.3 mm in diameter and Al2O3 shell of about 0.6 mm in thickness (Fig. 1(a)). After the second extrusion, both the rod (dark color) and shell (light color) become fine to be approx￾imately 250–300 and 100 Am, respectively, as shown in Fig. 1(b). The third passed bar showed a further refinement in the microstructure, thus it is impossible to distinguish the microstructural distribution under the same magnification (Fig. 1(c)). The highly magnified micrograph taken from P region in Fig. 1(c) indicates that the third passed filament Fig. 1. SEM micrographs of fibrous monolithic (Al2O3-C)/EVA composite filaments with passes of extrusion. a—first, b—second, c—third pass, and d—enlarged image of the third pass. 70 I.-C. Kang et al. / Materials Letters 59 (2005) 69–73