Characterization of Hydroxyapatite Coated Mg for Biomedical Applications
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MRS Advances © 2018 Materials Research Society DOI: 10.1557/adv.2018.476
Characterization of Hydroxyapatite Coated Mg for Biomedical Applications Jiajia Lin1, Qiaomu Tian2, Arash Aslani4, Huinan Liu1,2,3 1
Materials Science & Engineering Program, University of California, Riverside CA 92521 USA
2
Department of Bioengineering, University of California, Riverside CA 92521 USA
3
Biomedical Sciences Program, School of Medicine, University of California, Riverside CA 92521 USA
4
N2 Biomedical LLC, One Patriots Park, Bedford, MA 01730, USA
ABSTRACT: Magnesium (Mg) and its alloys have showed a promising potential for medical implant applications due to their attractive biocompatibility and mechanical strength. Despite these promising properties, the critical challenge with Mg-based implants is rapid degradation in physiological environment that results in early loss of mechanical strength and hydrogen gas accumulation at the local site. Hydroxyapatite (HA) coatings provide a sound solution for controlling Mg degradation at the bone interface. In this paper, HA coatings with different particle sizes, namely, microHA (mHA) and nanoHA (nHA), were deposited on Mg plates and rods with two different pressures using N2 Biomedical’s proprietary deposition process called IonTiteTM. Surface characterization of the deposited layers showed mHA coated Mg prepared at high pressure had more homogeneous HA particles distribution with less defects.
INTRODUCTION Mg is a potential material for temporary biomedical implant applications such as orthopaedics, craniomaxillofacial and cardiovascular implants [1-5]. Mg is biocompatible; the degradation products of Mg are non-toxic, and can be excreted and metabolized through the kidney [4]. Compared to conventional biomedical implants such as stainless steel, Co-Cr alloys and titanium-based alloys, Mg is biodegradable and thus does not require secondary surgeries for removal [6]. Mg has similar elastic modulus (40 GPa) and yield strength (126 GPa) to the cortical bone (elastic modulus is 3-20 GPa, yield strength is 104.9-114.3 GPa), which can reduce the stress-shielding effect while being adequate for load-bearing applications [7]. Moreover, Mg is osteoconductive and can promote new bone formation and enhance osteointegration [8]. However, fast degradation of Mg limits its usage as implants because rapid release of hydrogen gas and the OH- leads to increase of local pH that could affect cell proliferation and new tissue growth [5]. The fast degradation of Mg implants could result in early loss of mechanical integrity and strength before adequate tissue healing. Hydroxyapatite (HA) is a potential coating material for Mg because it can slow down the diffusion of water and other aggressive ions to attack the underlying Mg substrates and control the degradation rate of
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