The fabrication and characterization of dicalcium phosphate dihydrate-modified magnetic nanoparticles and their performance in hyperthermia processes in vitro Chun-han Hou a, b , Ching-wei Chen c , Sheng-mou Hou a, d , Yu-ting Li a , Feng-huei Lin a, * a Institute of Biomedical Engineering, College of Medicine and College of Engineering, National Taiwan University, Taipei, Taiwan b Department of Orthopaedic Surgery, National Taiwan University Hospital, Yun-Lin Branch, Yun-Lin County, Taiwan c Institute of Materials Science and Engineering, National Taipei University of Technology, Taipei, Taiwan d Department of Orthopaedic Surgery, National Taiwan University Hospital, Taipei, Taiwan article info Article history: Received 4 April 2009 Accepted 10 May 2009 Available online 6 June 2009 Keywords: Brushite Calcium phosphate Nanoparticle Nanocomposite Magnetism In vitro test abstract Many different types of magnetic particles have been developed for the purpose of hyperthermia cancer therapy. In this study, a magnetic nanoparticle based on dicalcium phosphate dihydrate (DCPD) was formed by co-precipitation method. Addition of different concentrations of ferrous chloride to DCPD can alter its material properties. Various physical, chemical and magnetic tests of the magnetic DCPD nanoparticles (mDCPD) were performed, including X-ray diffraction (XRD), inductively coupled plasma- optical emission spectrometer (ICP-OES), superconducting quantum interference device (SQUID), and transmission electron microscopy (TEM). The heating efficiency of mDCPD in alternating magnetic field was proved to be suitable for hyperthermia. The results of cytotoxicity tests (WST-1 and LDH assay) showed no harmful effect. The mDCPD showed relative cancer-killing ability without damaging normal cells in vitro. Ó 2009 Elsevier Ltd. All rights reserved. 1. Introduction Magnetic nanoparticles are being increasingly considered for hyperthermia cancer therapy because of the relatively lower number of side effects associated with them [1–3]. Iron oxide (maghemite g-Fe 2 O 3 or magnetite Fe 3 O 4 ) is frequently used in clinical or experimental settings of biotechnology [4]. Various magnetic nanoparticles of ferrimagnetic bioglass ceramics (FBCs) were developed recently, and aimed to provide magnetic proper- ties for MRI and hyperthermia purposes [5]. Nevertheless, during the preparation of FBC, it had to heat up to 800  C and then quenched to room temperature. Particle size, especially after further milling, is difficult to control at the nanoscale, and quasi- crystallization may occur during the thermal processing. This has made it difficult to synthesis magnetic bioglass nanoparticles [6], which has limited their potential clinical applications. This has led to a need for different forms of magnetic nanoparticles for clinical use. Furthermore, magnetic nanoparticles have also been proven useful in other applications, such as cell labeling [7]. Calcium phosphate ceramic (CPC) has good biocompatibility, little toxicity and an adequate biodegradable rate. Therefore, many studies have proved its efficacy as a bone substitute [8–11]. Its adequate biodegradable rate makes it a good drug delivery vehicle [12,13]. It has also been used quite often by dentists [14], as root canal fillers, drug delivery vehicles, or scaffolds in pulp tissue engineering [15]. It was also been modified to be used in vertebroplasy as potentially valuable alternative to polymethylmethacrylate (PMMA) [16]. There are different phases in the CPC system, such as: dicalcium phosphate dihydrate (DCPD, CaHPO 4 .2H 2 O), also called brushite; hydroxyapatite (HAP, Ca 10 (PO 4 ) 6 (OH) 2 ) and tricalcium phosphate (TCP, Ca 3 (PO 4 ) 2 ). Among them, DCPD is the most stable phase in the acid environment [17]. DCPD is not a magnetic ceramic, but the iron ions can substitute the calcium ions of DCPD and form a magnetic DCPD (mDCPD), which is a possible candidate for cancer hyper- thermia application. Thus, in this study, we synthesized mDCPD with different concentration of iron and evaluated their physical properties and cytotoxicity. In vitro tests to assess their potential for killing cancer cells during hyperthermia were then carried out. 2. Material and methods 2.1. DCPD synthesis DCPD was prepared by co-precipitation method: mixing equal Molality (0.2 M) of calcium hydroxide (Riedel-de Haen) aqueous solution and orthophosphoric acid (Riedel-de Haen, 85%) solution. The calcium hydroxide solution was slowly dropped into the orthophosphoric acid solution until the pH level reached 5.2. During this titration process, the rotation speed of stirrer was kept at 800 rpm with a constant * Corresponding author. Tel.: þ886 2 23123456x61449; fax: þ886 2 23940049. E-mail address: double@ntu.edu.tw (F.-h. Lin). Contents lists available at ScienceDirect Biomaterials journal homepage: www.elsevier.com/locate/biomaterials 0142-9612/$ – see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.biomaterials.2009.05.018 Biomaterials 30 (2009) 4700–4707