An X-ray micro-fluorescence study to investigate the distribution of Al, Si, P and Ca ions in the surrounding soft tissue after implantation of a calcium phosphate-mullite ceramic composite in a rabbit animal model Richard A. Martin • Zahira Jaffer • Garima Tripathi • Shekhar Nath • Mira Mohanty • Victoria FitzGerald • Pierre Lagarde • Anne-Marie Flank • Artemis Stamboulis • Bikramjit Basu Received: 12 May 2011 / Accepted: 18 August 2011 / Published online: 30 August 2011 Ó Springer Science+Business Media, LLC 2011 Abstract Synthetic calcium phosphates, despite their bioactivity, are brittle. Calcium phosphate- mullite com- posites have been suggested as potential dental and bone replacement materials which exhibit increased toughness. Aluminium, present in mullite, has however been linked to bone demineralisation and neurotoxicity: it is therefore important to characterise the materials fully in order to understand their in vivo behaviour. The present work reports the compositional mapping of the interfacial region of a calcium phosphate—20 wt% mullite biocomposite/soft tissue interface, obtained from the samples implanted into the long bones of healthy rabbits according to standard protocols (ISO-10993) for up to 12 weeks. X-ray micro- fluorescence was used to map simultaneously the distri- bution of Al, P, Si and Ca across the ceramic–soft tissue interface. A well defined and sharp interface region was present between the ceramic and the surrounding soft tissue for each time period examined. The concentration of Al in the surrounding tissue was found to fall by two orders of magnitude, to the background level, within *35 lm of the implanted ceramic. 1 Introduction The mineral component of bone and teeth are formed of hydroxyapatite (HA, Ca 10 (PO 4 ) 6 OH 2 ). Consequently, bio- compatible ceramics formed of HA have received consid- erable interest as potential bone replacement materials. However, pure synthetic HA is extremely brittle (fracture toughness: 0.6–1 MPa m 0.5 ) [1, 2]. To overcome this problem, researchers have attempted to synthesize HA and other calcium phosphate (CaP)-based composite materials, which have a better combination of physical properties than monolithic HA [2–7]. Crystalline aluminium oxide, also referred to as corundum, is one of the hardest materials known, scoring 9 on the Mohs scale of mineral hardness [8], and may therefore be added to improve the toughness and chemical durability of glasses and glass ceramics [9, 10]. We have recently developed a range of hydroxyapatite- mullite composites and calcium phosphate-mullite com- posites [11–13] with a view to addressing this issue. Mullite is a solid solution of aluminium oxide (alumina, Al 2 O 3 ) and silica (SiO 2 ). The general formula for mullite solid solution is Al (4?2x) Si (2-2x) O (10-x) , where x = 0.17 to 0.59. In the present case the formula for the mullite phase described herein is 3Al 2 O 3 .2SiO 2 (i.e. x = 0.25). The present work R. A. Martin (&) School of Engineering & Applied Sciences and Aston Research Centre for Healthy Ageing, University of Aston, Aston Triangle, Birmingham B4 7ET, UK e-mail: R.A.Martin@Aston.ac.uk Z. Jaffer Á A. Stamboulis Department of Metallurgy and Materials, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK G. Tripathi Á S. Nath Á B. Basu Laboratory for Biomaterials, Department of Materials Science and Engineering, Indian Institute of Technology, Kanpur, Uttar Pradesh, India M. Mohanty Division of Implant Biology, BMT Wing, Sree Chitra Tirunal Institute for Medical Science and Technology, Trivandrum, Kerala, India V. FitzGerald School of Physical Sciences, University of Kent, Canterbury, Kent CT2 7NH, UK P. Lagarde Á A.-M. Flank Synchrotron Soleil, L’Orme des Merisiers, BP 48, 91192 Gif/Yvette, France 123 J Mater Sci: Mater Med (2011) 22:2537–2543 DOI 10.1007/s10856-011-4428-y