In Vitro Apatite Formation on Polymer Substrates Irradiated by the Simultaneous Use of Oxygen Cluster and Monomer Ion Be
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1020-GG07-10
In Vitro Apatite Formation on Polymer Substrates Irradiated by the Simultaneous Use of Oxygen Cluster and Monomer Ion Beams Masakazu Kawashita, Rei Araki, and Gikan H Takaoka Ion Beam Engineering Experimental Laboratory, Kyoto University, Nishikyo-ku, Kyoto, 6158510, Japan
ABSTRACT Polyethylene (PE) and silicone rubber substrates were irradiated at an acceleration voltage of 7 kV and a dose of 1×1015 ions/cm2 by the simultaneous use of oxygen cluster and monomer ion beams, and then soaked in CaCl2 solution. Apatite-forming ability of the substrates was examined using a metastable calcium phosphate solution that had 1.5 times the ion concentrations of a normal simulated body fluid (1.5SBF). After the irradiation, the hydrophilic functional groups such as COOH and silicon oxide clusters (SiOx) were formed at the PE and silicone rubber surfaces, respectively. The hydrophilicity of the substrates was remarkably improved by the irradiation. The irradiated PE and silicone rubber substrates formed apatite in 1.5SBF, whereas unirradiated ones did not form it. These results suggest that the functional groups such as COOH groups and SiñOH groups induced apatite nucleation in 1.5SBF. INTRODUCTION Artificial ligaments which are two-dimensional polyethylene terephthalate (PET) fabrics have been used for reconstruction of damaged ligaments. In the reconstruction, the artificial ligaments are fixed to bone by using bone plug and staples. However, a long-term is often required for complete cure, because PET does not bond to living bone directly but bond to the bone through fibrous tissues and hence the fixation of the artificial ligaments becomes sometimes unstable. If the surface of PET is modified to show bone-bonding ability (i.e. bioactivity), it is believed that the term for complete cure can be shortened remarkably. In the case of indwelling catheters of silicone rubber, serious infection sometimes occurred owing to its poor biocompatibility. It is believed that such infection can be suppressed by apatite coating on the silicone rubber surface, since it is well known that apatite shows an excellent biocompatibility. If the surface of silicone rubber is modified to show bioactivity, apatite can be coated on the silicone rubber surface by soaking in aqueous solution supersatuared with respect to apatite such as simulated body fluid (SBF). In order to obtain bioactive polymers, we should form functional groups such as SiñOH and COOH groups effective for apatite nucleation, on the surface of polymers [1]. Various attempts to modify the polymer surface with the bioactive phase have been made [2,3], but it is difficult to form the bioactive phase stably on the surfaces of hydrophobic polymers such as PE and silicone rubber. The ion beam process has a high potential for surface modification of polymers. The predominant properties of the ion beam process are based on the ability to control the kinetic energy precisely by adjusting the acceleration energy. In addition, atomic, molecular and cluster
ions are available,
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