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Emaan Alsubhe

article posted 22 May 2017

Emaan Alsubhe is a Ph.D. student in the Institute for Materials Research at the University of Leeds. She completed her master degree on nanoscale science and technology in 2015 at University of Leeds. Her research interest focus on tissue engineering in terms of doping different concentration of iron ions on calcium phosphate minerals.

Antonios Anastasiou is a Marie Curie Fellow in University of Leeds and his research is focused on the development of new ceramic biomaterials for periodontal treatment with the use of femtosecond LASERS.

El Mostafa Raif gained a degree in Biochemistry, Cell Biology and Genetics in 1990 and completed his PhD in 1993 at the University of Bordeaux, France. He is currently Tissue Culture Facilities Manager in the Department of Oral Biology, University of Leeds School of Dentistry.

Animesh Jha is a professor and chair in Applied Materials Science at University of Leeds. His areas of expertise: glass and mineral science; fiber, bulk and waveguide glass/glass-ceramic device engineering; rare-earth lasers and amplifiers; pulsed laser processing; bone and dental tissue engineering.

Crystalline to Amorphous Phase Transformations of Calcium Phosphate by Doping with different Concentrations of Fe3+
E. Alsubhe,1*, A.D. Anastasiou1, E.M. Raif2 & A. Jha1

1School of Chemical and Process Engineering, University of Leeds, UK.
2Department of Oral Biology, Leeds Dental School, University of Leeds, UK

Different forms of calcium phosphate have been widely studied in the last decade as bone and dental enamel materials. Due to the chemical and structural similarity of these materials with the mineral content of human bone, such materials currently used for tissue restoration e.g. in bone regeneration, drug delivery and coatings for implants (1). One major drawback of using calcium phosphates alone is their poor mechanical properties. However, the properties of these minerals can be tailored by incorporating various ions (e.g. Fe3+, Sr3+, Er3+) into the crystal lattice. Recently there was an increasing interest in Fe3+-doped calcium phosphates due to the essential function of iron as a nutrient in cell functions and in supporting the angiogenesis via oxygen transport (2). Therefore, the aim of this study is to investigate the doping mechanism of different concentrations of Fe3+-ions on the brushite (CaHPO4.2H2O) structure, which is a well-documented calcium phosphate used as a biomaterial.

In this respect, different concentrations (0%, 5%, 10%, 20%, 30% and 40% mol) of Fe3+-doped brushite powders were investigated for structural and phase stability characterisation from room temperature to 1000C. The doping of Fe3+-ions was carried in the form of iron nitrate. Once the Fe3+-ion concentration reaches 20% mol the material progressively becomes more amorphous, which is the main aim of this presentation. The mechanism of crystalline-to- amorphous state transformation via solution and thermal processing of Fe3+-doped phosphates are analysed by characterising the structural changes using the X-ray powder diffraction, Raman and FTIR spectroscopy. The thermal analysis (simultaneous thermal analysis STA) technique has been adopted for characterizing the phase transformation and the enthalpy associated with the phase change. The thermal analysis results demonstrates that the heat treatment at 1000C in air for 5hrs initiates amorphous-to-crystalline phase transformation in samples doped with 30% mol Fe+ , however the samples doped with 40% Fe3+-ion remained amorphous after heat treatment. The reason for the stability of the amorphous phase is analysed in the context of CaO-P2O5-Fe2O3 phase diagrams.

Fig 1. The X-Ray powder diffraction of (0%, 10%, 30% and 40%) concentrations of Fe3+doped brushite a) starting materials after synthesis and b) after sintering at 1000 C in air for 5 hrs. Reference:

1. BARRRE, F., C.A. VAN BLITTERSWIJK and K. DE GROOT. Bone regeneration: molecular and cellular interactions with calcium phosphate ceramics. international Journal of Nanomedicine, 2006, 1(3), p.317.1.
2. HENTZE, M.W. and L.C. KHN. Molecular control of vertebrate iron metabolism: mRNA-based regulatory circuits operated by iron, nitric oxide, and oxidative stress. Proceedings of the National Academy of Sciences, 1996, 93(16), pp.8175-8182.