title: Strontium- and calcium-containing, titanium-stabilised phosphate-based glasses with prolonged degradation for orthopaedic tissue engineering.
abstract: Strontium- and calcium-releasing, titanium-stabilised phosphate-based glasses with a controlled degradation rate are currently under development for orthopaedic tissue engineering applications. Ca and/or Sr were incorporated at varying concentrations in quaternary phosphate-based glasses, in order to promote osteoinduction. Ti was incorporated at a fixed concentration in order to prolong degradation. Glasses of the general formula (P2O5)-(Na2O)-(TiO2)-(CaO)-(SrO) were prepared via the melt-quench technique. The materials were characterised by energy-dispersive X-ray spectroscopy, X-ray diffraction, (31)P magic angle spinning nuclear magnetic resonance, Fourier transform infrared spectroscopy, differential thermal analysis and density determination. The dissolution rate in distilled water was determined by measuring mass loss, ion release and pH change over a two-week period. In addition, the cytocompatibility and alkaline phosphatase activity of an osteoblast-like cell line cultured on the surface of glass discs was assessed. The glasses were shown to be amorphous and contained Q(1), Q(2) and Q(3) species. Fourier transform infrared spectroscopy revealed small changes in the glass structure as Ca was substituted with Sr and differential thermal analysis confirmed a decrease in crystallisation temperature with increasing Sr content. Degradation and ion release studies also showed that mass loss was positively correlated with Sr content. These results were attributed to the lower electronegativity of Sr in comparison to Ca favouring the formation of phosphate-based mineral phases. All compositions supported cell proliferation and survival and induced at least 2.3-fold alkaline phosphatase activity relative to the control. Glass containing 17.5 mol% Sr had 3.6-fold greater alkaline phosphatase activity than the control. The gradual release of Ca and Sr supported osteoinduction, indicating their potential suitability in orthopaedic tissue engineering applications.
authors.affiliation: Division of Biomaterials and Tissue Engineering, UCL Eastman Dental Institute, London, UK.
authors.forename: Mustafa
authors.initials: M
authors.lastname: Al Qaysi
authors.affiliation: Division of Biomaterials and Tissue Engineering, UCL Eastman Dental Institute, London, UK Department of Electronics and Communication Engineering, Tampere University of Technology, Tampere, Finland Adult Stem Cell Group, Institute of Biomedical Technology, University of Tampere, Tampere, Finland BioMediTech (Institute of Biosciences and Medical Technology), Tampere, Finland.
authors.forename: Nick J
authors.initials: NJ
authors.lastname: Walters
authors.affiliation: Division of Biomaterials and Tissue Engineering, UCL Eastman Dental Institute, London, UK Department of Chemistry, Faculty of Mathematical and Physical Sciences, University College London, London, UK.
authors.forename: Farzad
authors.initials: F
authors.lastname: Foroutan
authors.affiliation: Division of Biomaterials and Tissue Engineering, UCL Eastman Dental Institute, London, UK.
authors.forename: Gareth J
authors.initials: GJ
authors.lastname: Owens
authors.affiliation: Department of Nanobiomedical Science and BK21 Plus NBM Global Research Center for Regenerative Medicine, Dankook University, Cheonan, Republic of Korea Institute of Tissue Regeneration Engineering and College of Dentistry, Dankook University, Cheonan, Republic of Korea.
authors.forename: Hae-Won
authors.initials: HW
authors.lastname: Kim
authors.affiliation: Unit of Orthodontics, Department of Craniofacial Growth and Development, UCL Eastman Dental Institute, London, UK.
authors.forename: Rishma
authors.initials: R
authors.lastname: Shah
authors.affiliation: Division of Biomaterials and Tissue Engineering, UCL Eastman Dental Institute, London, UK Department of Nanobiomedical Science and BK21 Plus NBM Global Research Center for Regenerative Medicine, Dankook University, Cheonan, Republic of Korea j.knowles@ucl.ac.uk.
authors.forename: Jonathan C
authors.initials: JC
authors.lastname: Knowles
mesh_terms: D002118:Calcium / Q000737:chemistry*; D045744:Cell Line, Tumor; D005898:Glass; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D010710:Phosphates / Q000737:chemistry*; D013052:Spectrometry, X-Ray Emission; D017550:Spectroscopy, Fourier Transform Infrared; D013324:Strontium / Q000737:chemistry*; D023822:Tissue Engineering; D014025:Titanium / Q000737:chemistry*; D014961:X-Ray Diffraction
chemical_list: D010710:Phosphates; D014025:Titanium; D002118:Calcium; D013324:Strontium
keywords: Phosphate-based glass; biomaterial; calcium; strontium; tissue engineering