Title: Nano-scale manipulation of silicate-substituted apatite chemistry impacts surface charge, hydrophilicity, protein adsorption and cell attachment

Authors: N. Rashid, Ian S. Harding, Tom Buckland, Karin A. Hing

Addresses: IRC in Biomedical Materials, Department of Materials, School of Engineering and Materials, Queen Mary University of London, London E1 4NS, UK. ' Agamatrix Inc., 10 Manor Parkway, Salem, NH 03079, USA. ' ApaTech Ltd., 370 Centennial Avenue, Centennial Park, Elstree, Herts WD6 3TJ, UK. ' IRC in Biomedical Materials, Department of Materials, School of Engineering and Materials, Queen Mary University of London, London E1 4NS, UK

Abstract: This study characterised the effect of nano-scale variation in hydroxyapatite (HA) surface-chemistry, by manipulation of silicate substitution level, on surface charge, hydrophilicity, protein adsorption and cell attachment. Substitution with 0.4 wt% Si (SA04) had a significant impact on surface charge, but did not affect hydrophilicity as compared to stoichiometric HA. Increasing silicon content to 0.8 wt% (SA08) did not alter surface charge, but significantly increased hydrophilicity as compared to SA04. A silicon content of 1.5 wt% (SA15) significantly altered surface charge but showed no statistical variation in hydrophilicity as compared to SA08. Study of both competitive (serum) and single (fibronectin) protein adsorption, in addition to osteoblast-like cell attachment, demonstrated increased protein adsorption and cell attachment on SA08. In contrast protein adsorption to SA04 and SA15 showed equivalent to intermediate behaviour while cell attachment demonstrated impaired to equivalent performance as compared to HA. This data indicates that the enhanced bioactivity of SA08 may be related to the influence that surface physiochemical characteristics have on its interaction with serum proteins.

Keywords: surface physiochemistry; protein adsorption; cell attachment; nanoscale manipulation; nanomaterials; hydrophilicity; hydroxyapatite surface chemistry; surface charge; serum proteins.

DOI: 10.1504/IJNBM.2008.016877

International Journal of Nano and Biomaterials, 2008 Vol.1 No.3, pp.299 - 319

Available online: 26 Jan 2008 *

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