In Vitro Cell Adhesion and Detachment Behavior for Various Biomaterial Substrates
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IN VITRO CELL ADHESION AND DETACHMENT BEHAVIOR FOR VARIOUS BIOMATERIAL SUBSTRATES
MARY BETH SCHMIDT AND JOHN B. BRUNSKI Rensselaer Polytechnic Institute, Department of Biomedical Engineering, Troy, NY 12180
ABSTRACT Cell-biomaterial interactions for different material compositions were evaluated through quantitative examination of in vitro cell spreading behavior and shear-induced cell detachment. Biomaterial substrates consisted of identically prepared, well characterized bulk samples of implant grade cp Ti, Ti-6AI-4V, and Synamel. 3T3 fibroblasts were seeded on the substrate surfaces and incubated for 2 hours. Adherent cell morphology was then examined using scanning electron microscopy and digital image analysis. The cell detachment response was measured using a parallel plate flow chamber. When categorized according to observed cell morphology, projected cell areas were found to be lognormally distributed for all biomaterials and ln(cell area) was significantly greater for Synamel, while no difference existed between cp Ti and Ti-6AI-4V. In addition, the average post-shear fraction of adherent cells was significantly greater for Synamel substrates, as compared to cp Ti and Ti-6AI-4V substrates. The results from this study indicate that in vitro cell adhesion and detachment behavior are measurably influenced by biomaterial substrate composition. INTRODUCTION Secure tissue attachment to the surface of a load-bearing dental or orthopaedic implant is essential for the long term success of the implant. While clinical and in vivo experimental studies indicate that the morphology and mechanical strength of the tissue-implant interface are dependent, at least in part, on the surface composition of the implant material [1-5], these results are variable and often inconsistent. In contrast, cell culture techniques can provide a more precisely controlled means to identify biomaterial surface properties which may influence the tissue-implant interface. The objectives of this study were therefore to evaluate and compare cell adhesion and detachment behavior for several biomaterial compositions, in an effort to examine material-dependent variations in cell- biomaterial interactions. MATERIALS AND METHODS Biomaterial substrate preparation and characterization Substrates consisted of bulk samples of the following three commonly used dental and orthopaedic implant materials: grade 4 cp Ti (ASTM F-67), Ti-6A1-4V ELI (ASTM F- 136), and Synamel (dense, crystalline hydroxyapatite prepared by Calcitek, Inc.). All surfaces were polished to 600 grit using water-lubricated SiC polishing paper. In the final stage of polishing, the surface scratches were oriented in a parallel fashion, along the flow direction for the cell detachment experiments, in order to minimize the effects of surface roughness. The Synamel substrates used for cell detachment experiments consisted of an II mm diameter polished Synamel disc seated within a well in a polished cp Ti substrate, such that the polishing scratches were aligned and the surfaces were flush.
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