In Vitro Human Osteoblast Responses to Titanium Oxide-Based Surfaces with Varying Topology and Composition
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In Vitro Human Osteoblast Responses to Titanium Oxide-Based Surfaces with Varying Topology and Composition C. Andrew Collier1, Julien M. Paillard1, Athina E. Markaki2, James A. Curran3, Helen J. Griffiths1, and T. William Clyne1 1 Department of Materials Science and Metallurgy, University of Cambridge, Pembroke Street, Cambridge, CB2 3QZ, UK 2 Department of Engineering, University of Cambridge, Cambridge, CB2 1PZ, UK 3 Keronite International Ltd., Granta Park, Great Abingdon, Cambridge, CB21 6GP, UK ABSTRACT The surface topology and composition of prosthetic implant materials affect cell responses and are therefore important design features. Plasma electrolytic oxidation (PEO) is a surface modification technique that can be used to produce oxidized surfaces with various surface properties [1]. In this work, Ti-6Al-4V was PEO processed to give two surfaces with different morphologies but similar chemical composition. Surface characteristics were assessed using X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, stylus profilometry and contact angle measurement. In vitro culture of human foetal osteoblasts (HOB) was performed on the surfaces, to examine cell responses to them. Cellular proliferation, morphology and differentiation were examined, using the AlamarBlue assay, SEM imaging and an alkaline phosphatase (ALP) activity assay respectively. Additionally, the individual effects of oxides present in the PEO processed surfaces (rutile and anatase) on the cells were examined, by binding them in powder form to produce surfaces with similar morphology, but different composition. Changes in the topology and chemistry of the surfaces affected osteoblast response. HOB proliferated more on the rougher PEO surface, and also displayed greater ALP activity. Also, cells responded differently to surfaces containing just rutile or anatase, indicating that the chemical phase of titanium oxide is of consequence for implant design. INTRODUCTION This report presents the findings of an investigation into the in-vitro behavior of human foetal osteoblasts cultured on a series of different substrates based on titanium oxide possessing different surface topologies and phase compositions. The overriding aim of the experiments was to isolate the effects of surface morphology and chemistry on cell behavior, with a view to optimizing the surface characteristics of titanium-based coatings in order to promote desired responses from cells growing on them. EXPERIMENTAL Substrate Production Ti-6Al-4V alloy discs (15 mm in diameter and 1 mm thick) were polished with SiC paper up to P4000 and coated using a 30 kW constant power PEO processing rig (manufactured by Keronite Ltd.). Processing was performed in aqueous electrolyte containing 4.5 g dm-3 Na3PO4,
at an initial current density of 20 A dm-2, for 1 and 15 minute periods (“P1” and “P15” samples). Samples were cleaned by ultrasonic agitation in acetone and water for 20 minutes. Anatase and rutile powders (Sigma, UK) with initial mode particle sizes
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