Strontium-substituted calcium phosphates prepared by hydrothermal method under linoleic acid–ethanol solution W.M. Lam a , H.B. Pan a , Z.Y. Li a , C. Yang c , W.K. Chan b , C.T. Wong a , K.D.K. Luk a , W.W. Lu a, * a Department of Orthopaedics and Traumatology, The University of Hong Kong, Hong Kong, China b Department of Chemistry, The University of Hong Kong, Hong Kong, China c Department of Chemistry, The Hong Kong University of Science and Technology, Hong Kong, China Received 11 June 2009; received in revised form 9 July 2009; accepted 1 October 2009 Available online 3 November 2009 Abstract Strontium-incorporated calcium phosphates show potential in biomedical application, particularly the doped strontium may help to new bone formation. In this study, the particle was synthesized by hydrothermal treatment at 120 8C for 15 h. It was found that the phase purity and aspect ratio was significantly affected by the addition of linoleic acid due to reduction of solution pH. In particular, strontium played important role in the transformation of minerals. Below 20% solution of calcium substituted by strontium, only apatite was formed; above it, a mixture of apatite and DCPA was detected, and a-SrHPO 4 was formed if all calcium solutions were replaced by strontium. Meanwhile, the adsorption of fatty acid on crystal was detected by FTIR. In summary, the incorporated fatty acid not only affected the morphology, but also its composition. # 2009 Elsevier Ltd and Techna Group S.r.l. All rights reserved. Keywords: A. Powders: chemical preparation; D. Apatite; E. Biomedical applications 1. Introduction Poly(methyl methacrylate) (PMMA) has been widely used for bone cement to affix implants and remodel lost bone for several decades due to good biocompatibility, ease of handling, good biomechanical strength and cost-effectiveness. However, the disadvantage is frequently mentioned due to poor adhesion to bony surfaces. The attempts to increase its bioactivity have been extensively reported such as the addition of bioactive materials [1,2]. In particular recently, the incorporated strontium is showing great potential, such as coating on titanium [3], bone cement filler [4] and toothpaste [5]. It was found that strontium could enhance preosteoblast differentia- tion, inhibit osteoclast differentiation, and thus reduce osteoclast function [6], thus an oral drug – strontium ranelate (SrR) has been confirmed to be particularly effective in the treatment of osteoporosis for postmenopausal women [7]. As the main composition of bone and teeth, hydroxyapatite (HA) and related calcium phosphates play a special interest in orthopaedics treatment as bone filler and substitution materials. Therefore, the incorporation of strontium is particularly important to develop novel bioceramics for biomedical application, which can be prepared by sol–gel [8], hydrothermal synthesis [9], solid reaction [10] and wet method [11]. The substitution of calcium by strontium is expected to be easy on the basis of chemical similarity, but the distortion of crystal structure may be occurred due to larger ionic radius of strontium, thus the solubility increases attributing to the decrease of crystal stability [12], particularly, the release of strontium is expected to stimulate new bone formation. In human body, essential fatty acids are primarily used to produce hormone-like substances that regulate a wide range of functions, including blood pressure, blood clotting, blood lipid levels, immune response and inflammation response to injury infection. Thus, the incorporation of unsaturated fatty acid may decrease the risk of inflammation in orthopaedic treatment [13,14]. In particular, two of them linoleic acid (LA) and alpha- linolenic acid (ALA) cannot be produced by human itself, but are widely distributed in plant oils [15]. In addition, fatty acids www.elsevier.com/locate/ceramint Available online at www.sciencedirect.com Ceramics International 36 (2010) 683–688 * Corresponding author at: Department of Orthopaedics & Traumatology, The University of Hong Kong, L907, Lab block, 21 Sassoon Rd, Pokfulam, Hong Kong, China. Tel.: +852 28199595; fax: +852 28185210. E-mail address: wwlu@hkusua.hku.hk (W.W. Lu). 0272-8842/$36.00 # 2009 Elsevier Ltd and Techna Group S.r.l. All rights reserved. doi:10.1016/j.ceramint.2009.10.012