S Murphy

Publications (3)4.63 Total impact

• Article: The effect of ionic dissolution products of Ca-Sr-Na-Zn-Si bioactive glass on in vitro cytocompatibility.

  S Murphy, A W Wren, M R Towler, D Boyd
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  ABSTRACT: Many commercial bone grafts cannot regenerate healthy bone in place of diseased bone. Bioactive glasses have received much attention in this regard due to the ability of their ionic dissolution products to promote cell proliferation, cell differentiation and activate gene expression. Through the incorporation of certain ions, bioactive glasses can become therapeutic for specific pathological situations. Calcium-strontium-sodium-zinc-silicate glass bone grafts have been shown to release therapeutic levels of zinc and strontium, however the in vitro compatibility of these materials is yet to be reported. In this study, the in vitro cytocompatibility of three different calcium-strontium-sodium-zinc-silicate glasses was examined as a function of their ion release profiles, using Novabone® bioglass as a commercial comparison. Experimental compositions were shown to release Si(4+) ranging from 1 to 81 ppm over 30 days; comparable or enhanced release in comparison to Novabone. The maximum Ca(2+) release detected for experimental compositions was 9.1 ppm, below that reported to stimulate osteoblasts. Sr(2+) release was within known therapeutic ranges, and Zn(2+) release ranged from 0.5 to 1.4 ppm, below reported cytotoxic levels. All examined glass compositions show equivalent or enhanced in vitro compatibility in comparison to Novabone. Cells exposed to BT112 ionic products showed enhanced cell viabilities indicating cell proliferation was induced. The ion release profiles suggest this effect was due to a synergistic interaction between certain combinations and concentrations of ions. Overall, results indicate that the calcium-strontium-sodium-zinc-silicate glass compositions show equivalent or even enhanced in vitro compatibility compared to Novabone®.
  Journal of Materials Science Materials in Medicine 10/2010; 21(10):2827-34. · 2.32 Impact Factor
• Article: The effect of composition on ion release from Ca-Sr-Na-Zn-Si glass bone grafts.

  S Murphy, D Boyd, S Moane, M Bennett
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  ABSTRACT: Controlled delivery of active ions from biomaterials has become critical in bone regeneration. Some silica-based materials, in particular bioactive glasses, have received much attention due to the ability of their dissolution products to promote cell proliferation, cell differentiation and activate gene expression. However, many of these materials offer little therapeutic potential for diseased tissue. Incorporating trace elements, such as zinc and strontium, known to have beneficial and therapeutic effects on bone may provide a more viable bone graft option for those suffering from metabolic bone diseases such as osteoporosis. Rational compositional design may also allow for controlled release of these active ions at desirable dose levels in order to enhance therapeutic efficacy. In this study, six differing compositions of calcium-strontium-sodium-zinc-silicate (Ca-Sr-Na-Zn-Si) glass bone grafts were immersed in pH 7.4 and pH 3 solutions to study the effect of glass composition on zinc and strontium release in a normal and extreme physiological environment. The zinc release levels over 30 days for all zinc-containing glasses in the pH 7.4 solution were 3.0-7.65 ppm. In the more acidic pH 3 environment, the zinc levels were higher (89-750 ppm) than those reported to be beneficial and may produce cytotoxic or negative effects on bone tissue. Strontium levels released from all examined glasses in both pH environments similarly fell within apparent beneficial ranges--7.5-3500 ppm. Glass compositions with identical SrO content but lower ZnO:Na(2)O ratios, showed higher levels of Sr(2+) release. Whereas, zinc release from zinc-containing glasses appeared related to ZnO compositional content. Sustainable strontium and zinc release was seen in the pH 7.4 environment up to day 7. These results indicate that the examined Ca-Sr-Na-Zn-Si glass compositions show good potential as therapeutic bone grafts, and that the graft composition can be tailored to allow therapeutic levels of ions to be released.
  Journal of Materials Science Materials in Medicine 06/2009; 20(11):2207-14. · 2.32 Impact Factor
• Article: Analysis of γ-irradiated synthetic bone grafts by 29Si MAS-NMR spectroscopy, calorimetry and XRD

  D. Boyd, S. Murphy, M.R. Towler, A.W. Wren, S. Hayakawa
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  ABSTRACT: Ca–Sr–Zn–Si glasses have demonstrated excellent biocompatibility both in vitro using the MTT assay with L929 mouse fibroblast cells, and in vivo using healthy and ovariectomized female Wistar rats. However, the biological evaluation of the materials was performed on glass granules that were autoclaved, rather than γ-irradiated; the sterilisation procedure required prior to implantation of these materials in the human body. Given the fact that when a glass is exposed to ionizing radiation changes in its physical properties can take place, it is imperative to determine whether the structure of such glasses will be altered as a result of exposure to the typical amounts of γ-irradiation required to sterilise such materials prior to implantation. This paper examines the structure of Na–Ca–Sr–Zn–Si glasses using 29Si MAS-NMR, XRD and DTA and to evaluate the effect of 30 kGy γ-irradiation on their structure. The 29Si MAS-NMR results indicate that the peak maxima for each glass remains between −74 ppm and −79 ppm; a chemical shift for 29Si associated with Q1 units in silicate glasses, and that the local environment around the 29Si isotope remains unaltered as a result of exposure. Additional analysis (DTA and XRD) showed that the onset of the glass transition temperature, Tg (in the range 553 °C–619 °C depending on composition) typically remains unchanged, as a result of exposure to the ionizing radiation, as do the XRD diffractograms for each glass. Therefore it can be concluded that the use of 30 kGy γ-irradiation does not effect the local environment of the 29Si isotope in the glasses, nor does it significantly alter the XRD diffraction patterns or the Tg values for CaO–SrO–NaO–ZnO–SiO2 described in this work.
  Journal of Non-Crystalline Solids.