CERAMICS INTERNATIONAL Available online at www.sciencedirect.com Ceramics International ] (]]]]) ]]]–]]] On the use of nanoliposomes as soft templates for controlled nucleation and growth of hydroxyapatite nanocrystals under hydrothermal conditions A. Ramedani a , A. Yazdanpanah a , F. Moztarzadeh b , M. Mozafari c,n a Biomaterials Group, Faculty of New Science and Technology, Tehran University, P.O. Box 14395-1561, Tehran, Iran b Biomaterials Group, Faculty of Biomedical Engineering (Center of Excellence), Amirkabir University of Technology, P.O. Box 15875-4413, Tehran, Iran c Bioengineering Research Group, Nanotechnology and Advanced Materials Department, Materials and Energy Research Center (MERC), P.O. Box 14155-4777, Tehran, Iran Received 2 October 2013; received in revised form 2 February 2014; accepted 2 February 2014 Abstract Calcium phosphates are biocompatible materials with the composition closest in similarity to the mineral phase of bone. Among them, hydroxyapatite (HA) is shown to be the most promising bioactive compound widely used in bone tissue engineering applications. It has been shown that the preparation of HA with controlled morphology and size distribution may be beneficial to therapy of bone disease. In this study, a new method was developed for the synthesis of nano-HA particles in which nanoliposomes were used as nucleation sites for growth of HA crystals. Phase composition, morphology, particle size and the molecular structure of sediments were studied using X-ray diffraction techniques (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FTIR). The results showed that nanoliposomes could act as carriers for the crystal growth of nano-HA particles. The powder produced from liposome encapsulation contained hexagonal bipyramidal structures of HA with nanometer dimensions, spherical shapes, dense morphologies and a mean size of about 60 nm. Further investigation of the bioactivity and biocompatibility of this new class of biomaterials is being performed. & 2014 Elsevier Ltd and Techna Group S.r.l. All rights reserved. Keywords: Hydrothermal method; Hydroxyapatite; Nanoliposomes; Nanostructure 1. Introduction Hydroxyapatite (HA) is known to be the most important member of calcium phosphates’ family. HA is the main constituent of natural bone composition and is similar to natural bone tissue [1, 2]. It is highly biocompatible and is widely used in bone implants. Recent advancements in nanoscience and nano- technology have reignited investigations of nano-scale HA forma- tion in order to clearly define the small-scale properties of HA. It has been suggested that nano-HA may be an ideal biomaterial due to its good biocompatibility and bone integration ability [3, 4]. Nano-HA particles have attracted the attention of many scientists due to their increased molecular purity and mechanical properties of implants [5–8]. Size and shape of HA crystals are critical factors that impact the physical–chemical properties of the final product such as fracture strength, fracture toughness, surface characteristics, biocompatibility, and solubility of the particles. HA powders have various morphologies such as needle-like, spherical, plate-like, etc. [9]. Nano-HA particles are synthesized through several methods such as wet chemistry or hydrothermal methods. In these methods, in order to improve mechanical properties, rod-shaped HA was synthesized with Cetyltrimethy- lammonium bromide (CTAB), used as a controlling factor for the nucleation and growth of HA crystals [10–12]. A micelle is an aggregate of surfactant molecules dispersed in a liquid colloid. A surfactant, CTAB creates micellar structures which would act as nano-reactors for the synthesis of nanoscale HA [13]. When the CTAB concentration is close to the critical micelle concentration (CMC), the particles are almost spherical in shape. This could be explained in view of the fact that, at CMC, CTAB in aqueous solutions forms spherical micelles and, therefore, the obtained www.elsevier.com/locate/ceramint http://dx.doi.org/10.1016/j.ceramint.2014.02.005 0272-8842 & 2014 Elsevier Ltd and Techna Group S.r.l. All rights reserved. n Corresponding author. Tel.: þ98 21 22373717. E-mail address: mozafari.masoud@gmail.com (M. Mozafari). Please cite this article as: A. Ramedani, et al., On the use of nanoliposomes as soft templates for controlled nucleation and growth of hydroxyapatite nanocrystals under hydrothermal conditions, Ceramics International (2014), http://dx.doi.org/10.1016/j.ceramint.2014.02.005