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A Novel Surface Topographical Concept for Bone Implant G. Munir1, L. Di Silvio2, M.J. Edirisinghe1, W. Bonfield3 and J. Huang1 1 Department of Mechanical Engineering, University College London, Torrington Place, London WC1E 7JE, U.K.

2 Biomaterials, Biomimetics and Biophotonics, King’s College Dental Institute at Guy’s, King’s and St. Thomas’ Hospitals, Floor 17, Guy’s Tower, London SE1 9RT, U.K. 3 Department of Materials Science and Metallurgy, University of Cambridge, Pembroke Street Cambridge B2 QZ U.K.

ABSTRACT Template-assisted electrohydrodynamic atomization (TAEA) spraying deposition, a recently developed and an electric-driven jet-based technique has been used to prepare bioactive surface topography on titanium (Ti). Nanometer-scaled SiHA (nanoSiHA), which closely resembles the bone mineral, has been synthesized and deposited on Ti surfaces with a range of patterns, such as pillars and tracks. A human osteoblast (HOB) cell model has been used to evaluate the in vitro cellular responses to nanoSiHA deposition. alamarBlue™ assay showed that nanoSiHA patterns are able to encourage the attachment and growth of HOB cells in comparison to those of nanoSiHA coating. The preferential growth of HOB cells was found along and across the track, HOB cells were also found to stretch between two tracks. Image analysis of HOB cell responses to the size of nanoSiHA pattern showed that the length of HOB cells was proportional to the gaps between the tracks until reaching the maximum length of 110 μm. The results indicate that the distance between the structures is paramount over the width. Our study will pave the way to control and guide cellular responses for new generation of bone implants. INTRODUCTION Metal implants have been served mankind for over a century. Due to the inherent properties of metal, they can never mimic natural bone. Silicon substituted hydroxyapatite (SiHA) has become a highly attractive alternative to conventional bioactive HA (which closely resembles natural bone mineral) in bone replacement due to the significant improvement in the in vivo bioactivity and osteoconductivity. The effect of silicon and SiHA on the body has been well documented [1-4]. In addition to chemistry, surface topography has been found to positively impact cellular response and is able to enhance the life time of the implant [5]. Thus, the concept of a nano-sized silicon-substitute hydroxyapatite (nanoSiHA) coated implant with 3-D surface topographies to guide bone tissue remodelling, has become attractive. Recently, a new technique, template-assisted electrohydrodynamic atomization (TAEA) spraying, is of considerable interest in surface topography formation [6, 7]. TAEA has been developed from electrohydrodynamic atomization spraying, an electric-driven jet-based deposition method. The process also offers the attractive advantages of easy control of a large uniform area coverage, low cost, compatibility

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with micro-fabrication technology and suitable for industrial production. This technology incorporates nanosized calciu