Polymer Surface Modification Causes Change in Phenotypic Expression of Primary Bone Cells
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POLYMER SURFACE MODIFICATION CAUSES CHANGE IN PHENOTYPIC EXPRESSION OF PRIMARY BONE CELLS.
SEAN A. F. PEEL*, R. N. SODHI* AND TRAN MINH DUC**, JOHN E. DAVIES*# * Centre for Biomaterials, University of Toronto, 170 College Street, Toronto, ON, M5S 1A1, Canada. **ESCA Centre for Surface Nanoanalysis and Technology, University Claude Bernard Lyon 1, Lyon, France. ABSTRACT Primary rat bone marrow cells were cultured on bacteriological grade polystyrene dishes which had been treated in selected areas with concentrated sulphuric acid. X-ray photoelectron spectroscopy, angle-resolved and imaging modes, and atomic force microscopy showed that the acid treatment brought about both chemical and topographical changes in the substratum surface. While the bone marrow cells attached to both treated and untreated areas of the surfaces of the dishes, the distribution of early mineralized extracellular matrix in these areas was reproducibily different. Thus, using extracellular matrix deposition as a marker, modification of the polymer surface resulted in the cells adhering to treated and untreated areas exhibiting different phenotypes.
INTRODUCTION When primary bone cells are cultured on bacteriological grade polystyrene, their adhesive and migratory behaviour can be changed by first treating the substratum with concentrated sulphuric acid [1]. The treatment of polystyrene with sulphuric acid has been used since the 1970's as one method to increase surface energy and render this material suitable for cell attachment and spreading [2] by hydroxylating the polymer surface at both long chain and phenyl ring sites [3]. The ability of contact dependent cells to respond to gradations in surface energy has been known since the work of Carter who coined the term "haptotaxis" for this phenomenon [4]. Lydon and Clay [5] demonstrated the ability of BHK fibroblasts to align themselves parallel to the haptotactic boundary created by acid treatment of a polystyrene culture dish. Our results have also demonstrated that primary bone cells, isolated by trypsinization, initially demonstrate similar behaviour. Nevertheless, after a recovery period of several days such cells migrate across the haptotactic boundary [1]. Shay and Walker have shown that fibroblasts and epithelial cells will react differently to similar physico-chemical boundaries [6] indicating cell type specificity in these early cell/substratum interactions. While the above observations indicated that surface treatment was having a significant effect on early migratory cell behaviour, the effects of substratum modifications on phenotypic expression were not addressed. In particular, while previous reports have focussed on the use of cell lines for such experiments, the use of primary, fully functional, cells is, potentially, of greater relevance in both the biomaterials and diagnostics arenas for modelling reactions of connective tissue cells to artificial substrata. However, to our knowledge, little attention has been been paid to longer term effects of the substratum on matrix syn
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