Bone Cell Response to Ion Implanted Silicon Wafers
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BONE CELL RESPONSE TO ION IMPLANTED SILICON WAFERS
W.R. Walsh, L. Zou, T.P. Lefkoe, #J.C. Kelly and *C.R. Howlett Department of Orthopaedics, Brown University, Rhode Island Hospital Providence, RI 02906 * University of New South Wales- School of Pathology, # University of New South Wales - School of Physics, Sydney Australia
ABSTRACT Results of preliminary investigations on the electrokinetic characterization and osteoblast morphology of ion implanted silicon wafers are presented. The goal of this study is to modify the surface of a material via ion implantation to control cellular interactions at the prosthesis-body interface. INTRODUCTION The bone-prosthesis interface and the problems associated with aseptic loosening of total joint replacements remains a major problem in orthopaedics today. The adsorption of proteins and cells to a surface can be influenced by the topology, chemical constituents and surface charge of the substrata. Recently, the migratory morphology of osteoblasts have been shown to be influenced by adsorbed species at the material surface whose adsorbance is in turn affected by the electrical charge of the substrata [1]. The morphological appearance and biochemical functioning of cells can also be influenced by the electrical surface charge. Therefore, control of the charge of a surface offers a unique way to dictate the biochemical output from a cell and possibly influence the nature of the bone-prosthesis interface. Surface modifications of prosthetic implants through ion beam implantation have been used to control corrosion and charge-injection capabilities of various surgical alloys [2], as well as mechanical modification (pitted surfaces) for cell growth [3]. In addition to controlling the electrochemical aspects of corrosion, ion implantation also offers the hope of being able to change and control the chemical and electrical nature of the surface of a prosthetic implant, controlling tissue adhesion and possibly having a positive influence on the biochemical output, while retaining the bulk of mechanical properties [4]. Ion beam implantation has a further advantage of penetrating into the material and being more adherent and durable than a surface coating method [4]. Ion implantation also offers an economical method with the requirement of only small quantities to modify the charge characteristics of a surface. The interface between a charge solid and ionic containing fluid will result in a charge separation and the establishment of an electrical double layer. The adsorption
Mat. Res. Soc. Symp. Proc. Vol. 252. c 1992 Materials Research Society
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of organic material and other macromolecules to a charged surface will be influenced by the characteristic of the electrical double layer. The electrical environment the cell "senses" will also influence its morphological and biochemical behavior. Therefore, a streaming potential technique was employed to characterize the electrokinetic characteristics for ion implanted silicon wafers. Bone cells (osteoblasts) were subsequently grown on t
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