Nanotoxicology, 2011; Early Online, 1–15 © 2011 Informa UK, Ltd. ISSN: 1743-5390 print / 1743-5404 online DOI: 10.3109/17435390.2011.600839 Development and haematotoxicological evaluation of doped hydroxyapatite based multimodal nanocontrast agent for near-infrared, magnetic resonance and X-ray contrast imaging Anusha Ashokan, Parwathy Chandran, Aparna R. Sadanandan, Chaitanya K. Koduri, Archana P. Retnakumari, Deepthy Menon, Shantikumar Nair & Manzoor Koyakutty Amrita Centre for Nanoscience and Molecular Medicine, Amrita Institute of Medical Sciences, Amrita Vishwa Vidyapeetham University, Cochin, Kerala, India Abstract Multimodal molecular imaging provides both anatomical and molecular information, aiding early stage detection and better treatment planning of diseased conditions. Here, we report development and nanotoxicity evaluation of a novel hydroxyapatite nanoparticle (nHAp) based multimodal contrast agent for combined near-infrared (NIR), MR and X-ray imaging. Under optimised wet-chemical conditions, we achieved simultaneous doping of nHAp (size ~50 nm) with indocyanine green and Gd 3+ contributing to NIR contrast (~750–850 nm), paramagnetic behaviour and X-ray absorption suitable for NIR, MR and X-ray contrast imaging, respectively. Haematocompatibility studies using stem cell viability, haemolysis, platelet activation, platelet aggregation and coagulation time analysis indicated excellent compatibility of doped nHAp (D-nHAp). Further, the immunogenic function studies using human lymphocytes (in vitro) showed that D-nHAp caused no adverse effects. Collectively, our studies suggest that D-nHAp with excellent biocompatibility and multifunctional properties is a promising nanocontrast agent for combined NIR, MR and X-ray imaging applications. Keywords: Hydroxyapatite nanoparticles, near-infrared imaging, MRI, X-ray contrast, haematotoxicity Introduction Multimodal molecular imaging (MMI) involving combinato- rial imaging techniques such as X-ray, near-infrared (NIR) fluorescence and MR can make significant advances in the diagnosis and therapy of complex diseases such as cancer (Jaffer et al. 2009; Moore et al. 2004; Ashokan et al. 2010). In addition to the gross anatomical features obtained through X-ray or MRI, the fluorescent component in MMI can provide more specific molecular characteristics of the disease, thus enabling early stage diagnosis and improvement in image-guided therapy (Bartlett et al. 2007; Li et al. 2008; Weissleder et al. 2005; Vizard et al. 2010). Recently, a number of bi-modal nanocontrast agents have been reported for com- bined magnetic and fluorescent imaging (Choi et al. 2006; Kircher et al. 2003; Kim et al. 2007; Lee et al. 2006; Santra et al. 2005). In most of these systems, the magnetic contrast agent forms the core while the optical component embedded within a polymer or protein platform forms the shell (Kircher et al. 2003). Alternatively, both the magnetic and fluorescent parts may be embedded within a nano-platform such as polymers (Kim et al. 2008), lipids (Mulder et al. 2006), liposomes (Strijkers et al. 2010), lipoproteins (Cormode et al. 2008) or inorganic materials such as silica (Rieter et al. 2007). However, one of the major limitations of such multimodal systems is the toxicity associated with individual nano-components. For example, quantum dots that form the fluorescent component in most of these systems appear to be highly toxic (Derfus et al. 2004), and hence pose problems for in vivo applications. Recently, we have developed a highly bio-compatible all- inorganic multimodal nanocontrast agent based on hydroxy- apatite (HAp) for simultaneous X-ray, fluorescence and mag- netic imaging (Ashokan et al. 2010). HAp (Ca 10 (PO 4 ) 6 (OH) 2 ) is the bio-mineral component of human bone and teeth and hence highly biocompatible. Recently, synthetically prepared Ca 3 (PO 4 ) 2 nanoparticles were successfully used for the delivery of genes (Sokolova et al. 2006), siRNA (Sokolova et al. 2007), chemodrugs (Kester et al. 2008) as well as for imaging applica- tions (Altinoglu et al. 2008). In our earlier work, we have shown that, by suitable doping with rare-earth impurities (Eu 3+ and Gd 3+ ), synthetic nanoparticles of phase pure HAp can be engineered to provide multifunctional contrast properties. Correspondence: Manzoor Koyakutty and Shantikumar Nair, Amrita Institute of Medical Sciences, Amrita Centre for Nanoscience and Molecular Medicine, Amrita Vishwa Vidyapeetham University, Cochin, Kerala, India. Tel: +91 484 2801234. Fax: +91 484 2802020. E-mail: manzoork@aims.amrita.edu, E-mail: shantinair@aims.amrita.edu (Received 22 March 2011; accepted 23 June 2011)  Nanotoxicology Downloaded from informahealthcare.com by 122.181.142.195 on 07/22/11 For personal use only.