Daniel Boyd

Dalhousie University, Halifax, Nova Scotia, Canada

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Publications (77)145.63 Total impact

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    ABSTRACT: In this study, nine phosphate-based glass formulations from the system P2 O5 -CaO-Na2 O-MgO-B2 O3 were prepared with P2 O5 content fixed as 40, 45 and 50 mol%, where Na2 O was replaced by 5 and 10 mol% B2 O3 and MgO and CaO were fixed to 24 and 16 mol%, respectively. The effect of B2 O3 addition on the viscosity-temperature behaviour, fragility index and structure of the glasses was investigated. The composition of the glasses was confirmed by ICP-AES. The viscosity-temperature behaviour of the glasses were measured using beam-bending and parallel -plate viscometers. The viscosity of the glasses investigated was found to shift to higher temperature with increasing B2 O3 content. The kinetic fragility parameter, m and F1/2 , estimated from the viscosity curve were found to decease with increasing B2 O3 content. The structural analysis was achieved by a combination of Fourier transform infrared spectroscopy and solid state nuclear magnetic resonance. (31) P solid-state magic-angle-spinning nuclear magnetic resonance (MAS-NMR) showed that the local structure of the glasses changes with increasing B2 O3 content. As B2 O3 was added to the glass systems, the phosphate connectivity increases as the as the Q(1) units transforms into Q(2) units. The (11) B NMR results confirmed the presence of tetrahedral boron (BO4 ) units for all the compositions investigated. Structural analysis indicates an increasing level of cross-linking with increasing B2 O3 content. Evidence of the presence of P-O-B bonds was also observed from the FTIR and (31) P NMR analysis. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2016.
    No preview · Article · Jan 2016 · Journal of Biomedical Materials Research Part B Applied Biomaterials
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    ABSTRACT: A host of research opportunities with innumerable clinical applications are open to biomedical glasses if one considers their potential as therapeutic inorganic ion delivery systems. Generally, applications have been limited to repair and regeneration of hard tissues while compositions are largely constrained to the original bioactive glass developed in the 1960s. However, in oncology applications the therapeutic paradigm shifts from repair to targeted destruction. With this in mind, the composition-structure-property-function relationships of vanadium-containing zinc-silicate glasses (0.51SiO2-0.29Na2O-(0.20-X)ZnO-XV2O5, 0 ≤ X ≤ 0.09) were characterized in order to determine their potential as therapeutic inorganic ion delivery systems. Increased V2O5 mole fraction resulted in a linear decrease in density and glass transition temperature (Tg). (29)Si MAS NMR peak maxima shifted upfield while (51)V MAS NMR peak maxima were independent of V2O5 content and overlapped well with the spectra NaVO3. Increased V2O5 mole fraction caused ion release to increase. When human liver cancer cells, HepG2, were exposed to these ions they demonstrated a concentration-dependent cytotoxic response, mediated by apoptosis. This work demonstrates that the zinc-silicate system studied herein is capable of delivering therapeutic inorganic ions at concentrations that induce apoptotic cell death and provide a simple means to control therapeutic inorganic ion delivery.
    Full-text · Article · Dec 2015 · Journal of Biomaterials Applications
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    ABSTRACT: Two series of lanthanum containing zinc-silicate glasses were developed (A: 0.51SiO2-0.29Na2O-(0.20-X)ZnO-XLa2O3, 0 & X 0.09; B: 0.51SiO2-0.35ZnO-(0.14-Y)Na2O-YLa2O3, 0 Y ; 0.14). Glasses were characterized in order to examine composition-structure-property-function relationships with a view to their potential use as therapeutic inorganic ion delivery systems. Glasses were melt synthesized and the role of lanthanum was investigated with respect to (i) glass structure based on density, glass transition temperature (Tg) and 29Si MAS-NMR, (ii) the effect on radiopacity (computed tomography) as a function of composition and (iii) the ion release characteristics under simulated physiological conditions. A linear increase in density and Tg was observed with the addition of La2O3 to each glass series. Generally, glasses demonstrated a constant molar volume, while density was observed to increase linearly with the addition of La2O3. The peak maxima of the 29Si MAS NMR spectra remained relatively unchanged by the addition of La2O3 in both glass series, but the line shapes and widths reveal modifications in the local silica structure. Radiopacity increased with La2O3: series A ranged between 1770 ± 33 and 6590 ± 89 HU and B Series B ranged between 2340 ± 54 and 9120 ± 290 HU. Series A glasses were observed to release only Na, it was also noted that increased La2O3 caused a reduction in Na+ release. Series B glasses released all constituent glass elements. Interestingly, in series B, La3 + concentration decreased over time indicating possible reprecipitation. Based on the structural data, lanthanum does not behave as a traditional network modifier and may in fact act to stabilize the network against degradation by the formation of mixed cation clusters.
    No preview · Article · Dec 2015 · Journal of Non-Crystalline Solids
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    ABSTRACT: The effect of increasing substitutions of La2O3:Na2O on the structure (11B MAS NMR) and properties, specifically strontium (Sr) ion release from five quaternary borate glass compositions (B2O3-SrO-Na2O-La2O3) was studied. To examine component ion release, samples were extracted under simulated physiological conditions at 37 °C for five extraction time points (24, 72, 168, 336 and 720 h). A linear release profile for strontium was provided by composition LB102 (70B2O3-20SrO-6Na2O-4La2O3) for up to 720 h. 11B MAS NMR was used to investigate the impact of La2O3:Na2O substitution on the boron structure and speciation. Substitutions appeared to have minor effects on borate speciation, with the only change being a decrease in the proportion of BO4 at maximum La2O3 loading (70B2O3-20SrO-10La2O3). These data further demonstrate the possible utility of high boron glasses as controllable degradable materials for the delivery of therapeutic metal ions, such as strontium.
    Full-text · Article · Dec 2015 · Journal of Non-Crystalline Solids
  • Caitlin M. Pierlot · Lauren Kiri · Daniel Boyd
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    ABSTRACT: Glass ionomer cements have been discussed across broad and progressive applications from dentistry to orthopedics. However, in orthopedic applications, adverse patient outcomes that have been clinically linked to the release of aluminum from conventional alumino-silicate GICs, demonstrate a critical need for the development of new aluminum-free materials. Accordingly, the present study uses an Ames Screen to evaluate the preliminary genotoxicity profiles of a series of promising new germanium-containing, aluminum-free GICs. The results herein reveal that in addition to the already demonstrated superior handling characteristics and suitable mechanical strength, these cements are non-mutagenic to bacteria strains S. typhimurium (TA98) and E. coli (WP2uvrA). The results of this study provide strong positive evidence regarding the genotoxicity of these novel GICs, warranting further investigation into the biocompatibility of these materials for numerous in vivo applications.
    No preview · Article · Dec 2015
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    ABSTRACT: Titanium (Ti(4+) ) containing materials have been widely used in medical applications due to its associated bioactivity in vivo. This study investigates the replacement of Si(4+) with Ti(4+) within the system SiO2 -Na2 O-CaO-P2 O5 to determine its influence on glass structure. This strategy was conducted in order to control the glass solubility to further improve the cellular response. Ti(4+) incorporation was found to have little influence on the glass transition temperature (Tg = 520 ± 8°C) and magic angle spinning-nuclear magnetic resonance (MAS-NMR) shifts (-80 ppm) up to additions of 18 wt %. However, at 30 wt % the Tg increased to 600°C and MAS-NMR spectra shifted to -88 ppm. There was also an associated reduction in glass solubility as a function of Ti(4+) incorporation as determined by inductively coupled plasma optical emission spectroscopy where Si(4+) (1649-44 mg/L) and Na(+) (892-36 mg/L) levels greatly reduced while Ca(2+) (3-5 mg/L) and PO43- (2-7 mg/L) levels remained relatively unchanged. MC3T3 osteoblasts were used for cell culture testing and it was determined that the Ti(4+) glasses increased cell viability and also facilitated greater osteoblast adhesion and proliferation to the glass surface compared to the control glass. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2015.
    No preview · Article · Sep 2015 · Journal of Biomedical Materials Research Part B Applied Biomaterials
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    ABSTRACT: Glass polyalkenoate cements (GPCs) have been used in dentistry for over 40 years. These novel bio-active materials are the result of a reaction between a finely ground glass (base) and a polymer (acid), usually poly(acrylic acid) (PAA), in the presence of water. This article reviews the types of PAA used as reagents (including how they vary by molar mass, molecular weight, concentration , polydispersity and content) and the way that they control the properties of the conventional GPCs (CGPCs) formulated from them. The article also considers the effect of PAA on the clinical performance of CGPCs, including biocompatibility, rheological and mechanical properties, adhesion, ion release, acid erosion and clinical durability. The review has critically evaluated the literature and clarified the role that the polyacid component of CGPCs plays in setting and maturation. This review will lead to an improved understanding of the chemistry and properties of the PAA phase which will lead to further innovation in the glass-based cements field.
    Full-text · Article · Jul 2015 · Journal of Polymer Engineering
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    Lauren Kiri · Mark Filiaggi · Daniel Boyd
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    ABSTRACT: Chemotherapeutic-loaded bone cement may be an effective method of drug delivery for the management of cancer-related vertebral fractures that require cement injection for pain relief. Recent advancements in the development of aluminum-free glass ionomer cements (GICs) have rendered this class of biomaterials clinically viable for such applications. To expand the therapeutic benefits of these materials, this study examined, for the first time, their drug delivery potential. Through incrementally loading the GIC with methotrexate (MTX) by up to 10-wt%, composition-property relationships were established, correlating MTX loading with working time and setting time, as well as compressive strength, drug release, and cytotoxic effect over 31 days. The most significant finding of this study was that MTX was readily released from the GIC, while maintaining cytotoxic activity. Release correlated linearly with initial loading and appeared to be diffusion mediated, delivering a total of 1-2% of the incorporated drug. MTX loading in this range exerted minimal effects to handling and strength, indicating the clinical utility of the material was not compromised by MTX loading. The MTX-GIC systems examined herein are promising materials for combined structural delivery applications. © The Author(s) 2015 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav.
    Preview · Article · May 2015 · Journal of Biomaterials Applications
  • Lauren Kiri · Daniel Boyd
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    ABSTRACT: Adjusting powder-liquid ratio (P/L) and polyacrylic acid concentration (AC) has been documented as a means of tailoring the handling and mechanical properties of glass ionomer cements (GICs). This work implemented a novel approach in which the interactive effects of these two factors on three key GIC properties (working time, setting time, and compressive strength) were investigated using a central composite design of experiments. Using nonlinear regression analysis, formulation-property relationships were derived for each property, which enabled prediction of an optimal formulation (P/L and AC) through application of the desirability approach. A novel aluminum free GIC was investigated, as this material may present the first clinically viable GIC for use in injectable spinal applications, such as vertebroplasty. Ultimately, this study presents the first series of predictive regression models that explain the formulation-dependence of a GIC, and the first statistical method for optimizing both P/L and AC depending on user-defined inputs. Copyright © 2015 Elsevier Ltd. All rights reserved.
    No preview · Article · Feb 2015 · Journal of the Mechanical Behavior of Biomedical Materials
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    ABSTRACT: The purpose of this study was to synthesize and optimize intrinsically radiopaque composite embolic microspheres for sustained release of doxorubicin in drug-eluting bead transarterial chemoembolization. Using a design of experiments approach, 12 radiopaque composites composed of polylactic-co-glycolic acid and a radiopaque glass (ORP5) were screened over a range of compositions and examined for radiopacity (computed tomography) and density. In vitro cell viability was determined using an extract assay derived from each composition against the human hepatocellular carcinoma cell line, HepG2. Mathematical models based on a D-Optimal response surface methodology were used to determine the preferred radiopaque composite. The resulting radiopaque composite was validated and subsequently loaded with doxorubicin between 0 and 1.4% (wt% of polylactic-co-glycolic acid) to yield radiopaque composite drug-eluting beads. Thereafter, the radiopaque composite drug-eluting beads were subjected to an elution study (up to 168 h) to determine doxorubicin release profiles (UV-Vis spectroscopy) and in vitro cell viability. Radiopaque composites evaluated for screening purposes had densities between 1.28 and 1.67 g.cm(-3), radiopacity ranged between 211 and 1450HU and cell viabilities between 91 and 106% were observed. The optimized radiopaque composite comprised 23 wt% polylactic-co-glycolic acid and 60 wt% ORP5 with a corresponding density of 1.63 ± 0.001 g.cm(-3), radiopacity at 1930 ± 44HU and cell viability of 89 ± 7.6%. Radiopaque composite drug-eluting beads provided sustained doxorubicin release over 168 h. In conclusion, the mathematical models allowed for the identification and synthesis of a unique radiopaque composite. The optimized radiopaque composite had similar density and cell viability to commercially available embolic microspheres. It was possible to preload doxorubicin into radiopaque composite drug-eluting beads, such that sustained release was possible under simulated physiological conditions. © The Author(s) 2015 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav.
    No preview · Article · Feb 2015 · Journal of Biomaterials Applications

  • No preview · Article · Feb 2015 · Journal of Vascular and Interventional Radiology
  • S. Kehoe · R. Abraham · D. Boyd

    No preview · Article · Feb 2015 · Journal of Vascular and Interventional Radiology
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    ABSTRACT: Intrinsically radiopaque (imageable) microspheres for transarterial embolization (TAE) are required to enable real-time intraprocedural feedback and definition of spatial distribution patterns of embolic materials in target tissues. This pilot study evaluates acute and sub-chronic safety and efficacy of imageable zinc-silicate (Zn-Si) glass microspheres in a swine renal artery embolization (RAE) model. Eight swine were divided into two cohorts. Clinical determinants of embolization effectiveness, including imageability, deliverability and temporal/ spatial distribution of microspheres in target tissues were assessed. Subsequently, cohort I and II were used to evaluate the acute and subchronic host response against the Zn-Si microspheres versus a clinical control. The developed microspheres provide for direct intraprocedural feedback using standard diagnostic imaging techniques. Fluoroscopy correlated with ex-vivo high-resolution radiography, CT and micro-CT, demonstrating high imageability, excellent spatial distribution and packing of the Zn- Si microspheres. At follow-up, infarction of the embolized kidneys was noted without any major adverse tissue reaction. Mild recanalization was observed microscopically for both experimental and control microspheres. Zn-Si microspheres permit the definition of spatial distribution in a target tissue, consequently permitting the optimization, personalization and improvement of TAE techniques.
    No preview · Article · Jan 2015
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    ABSTRACT: Aluminum-free glass ionomer cements (GICs) are under development for orthopedic applications, but are limited by their insufficient handling properties. Here, the addition of calcium polyphosphate (CPP) was investigated as an additive to an experimental zinc-silicate glass ionomer cement. A 50% maximum increase in working time was observed with CPP addition, though this was not clinically significant due to the short working times of the starting zinc-silicate GIC. Surprisingly, CPP also improved the mechanical properties, especially the tensile strength which increased by ∼33% after 30 days in TRIS buffer solution upon CPP addition up to 37.5 wt%. This strengthening may have been due to the formation of ionic crosslinks between the polyphosphate chains and polyacrylic acid. Thus, CPP is a potential additive to future GIC compositions as it has been shown to improve handling and mechanical properties. In addition, CPP may stimulate new bone growth and provide the ability for drug delivery, which are desirable modifications for an orthopedic cement. © The Author(s) 2015 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav.
    No preview · Article · Jan 2015 · Journal of Biomaterials Applications
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    ABSTRACT: This short communication determines the strength of two glass polyalkenoate cements that differ from each other through the composition of their glass phase. Sample sets of n=5, 10, 20 and 30 were formulated and tested in biaxial flexure. The derived mean for each sample set was compared against the Weibull characteristic strength. The mean and corresponding characteristic strength show a maximum percentage difference 10.1%, and the 95% confidence intervals calculated from the mean data encompass the corresponding characteristic strength down to a sample set of n=5. This suggests that, for brittle materials such as glass polyalkenoate cements, it is acceptable to test only five samples of each material in biaxial flexure and the resultant 95% confidence intervals will encompass the corresponding Weibull characteristic strength of the material. Copyright © 2014 Elsevier Ltd. All rights reserved.
    Full-text · Article · Dec 2014 · Journal of the Mechanical Behavior of Biomedical Materials
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    ABSTRACT: Non-classical ionomer glasses like those based on zinc-boron-germanium glasses are of special interest in a variety of medical applications owning to their unique combination of properties and potential therapeutic efficacy. These features may be of particular benefit with respect to the utilization of glass ionomer cements for minimally invasive dental applications such as the atruamatic restorative treatment, but also for expanded clinical applications in orthopedics and oral-maxillofacial surgery. A unique system of zinc-boron-germanium-based glasses (10 compositions in total) has been designed using a Design of Mixtures methodology. In the first instance, ionomer glasses were examined via differential thermal analysis, X-ray diffraction, and (11)B MAS NMR spectroscopy to establish fundamental composition - structure-property relationships for the unique system. Secondly, cements were synthesized based on each glass and handling characteristics (working time, Wt, and setting time, St) and compression strength were quantified to facilitate the development of both experimental and mathematical composition-structure-property relationships for the new ionomer cements. The novel glass ionomer cements were found to provide Wt, St, and compression strength in the range of 48-132 s, 206-602 s, and 16-36 MPa, respectively, depending on the ZnO/GeO2 mol fraction of the glass phase. A lower ZnO mol fraction in the glass phase provides higher glass transition temperature, higher N4 rate, and in combination with careful modulation of GeO2 mol fraction in the glass phase provides a unique approach to extending the Wt and St of glass ionomer cement without compromising (in fact enhancing) compression strength. The data presented in this work provide valuable information for the formulation of alternative glass ionomer cements for applications within and beyond the dental clinic, especially where conventional approaches to modulating working time and strength exhibit co-dependencies (i.e. the enhancement of one property comes at the expense of the other) and therefore limit development strategies.
    No preview · Article · Nov 2014 · Journal of Biomaterials Applications
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    ABSTRACT: We have synthesized TiO2 doped strontium borate glasses, 70B2O3-(30-x)SrO-xTiO2 and 70B2O3-20SrO(10-x)Na2O-xTiO2. The composition dependence of glass structure, density, thermal properties, durability and cytotoxicity of degradation products was studied. Digesting the glass in mineral acid and detecting the concentrations of various ions using an ICP provided the actual compositions that were 5-8% deviated from the theoretical values. The structure was investigated by means of 11B magic angle spinning (MAS) NMR spectroscopy. DSC analyses provided the thermal properties and the degradation rates were measured by measuring the weight loss of glass disc-samples in phosphate buffered saline at 37 C in-vitro. Finally the MTT assay was used to analyse the cytotoxicity of the degradation products. The structural analysis revealed that replacing TiO2 for SrO or Na2O increased the BO3/BO4 ratio suggesting the network-forming role of TiO2. Thermal properties, density and degradation rates also followed the structural changes. Varying SrO content predominantly controlled the degradation rates, which in turn controlled the ion release kinetics. A reasonable control (2-25% mass loss in 21 days) over mass loss was achieved in current study. Even though very high concentrations (up to 5500ppm B, and 1200ppm Sr) of ions were released from the ternary glass compositions, that saturated the degradation media in 7 days, the degradation products from ternary glass system was found non-cytotoxic. However, quaternary glasses demonstrated negative affect on cell viability due to very high (7000ppm) Na ion concentration. All the glasses investigated in current study are deemed fast degrading with further control over degradation rates, release kinetics desirable.
    No preview · Article · Nov 2014 · Journal of Biomedical Materials Research Part A
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    ABSTRACT: Si–Ca–Zn–La–Ti–Mg–Sr–Na glasses have demonstrated excellent biocompatibility both in vitro using the MTT/LDH assays (with L929 mouse fibroblast cells and human blood platelets), and in vivo using New Zealand White rabbits. However, the biological evaluation of the materials was performed on as-manufactured glass granules that were autoclaved, rather than aged or γ-irradiated glass microspheres; the sterilization procedure required prior to implantation of these materials in its final form inside the human body. Given the fact that when a glass is subjected to aging either accelerated or natural changes in its physical properties can take place, it is imperative to determine whether the structure of such glasses will be altered over time in order to substantiate shelf-life claims. The structure of such glasses may also be altered as a result of exposure to the typical amounts of γ-irradiation required to sterilize such materials prior to implantation. This paper therefore examines the structure of Si–Ca–Zn–La–Ti–Mg–Sr–Na glasses using XRD, DSC, pycnometry, 29Si MAS-NMR and ICP–OES to evaluate both the effect of accelerated aging and multiple cycles of 30 kGy γ-irradiation on their structure and subsequent radiopacity. The 29Si MAS-NMR results indicate that the peak maxima for each glass remain between − 83 ppm and − 86 ppm; a chemical shift for 29Si associated with Q2 to Q3 units in silicate glasses, and that the local environment around the 29Si isotope remains unaltered as a result of aging or exposure. Additional analysis (XRD, DSC, pycnometry, ICP–OES and radiopacity) showed that the glass transition temperature, Tg (676 ± 4 °C) typically remains unchanged, as a result of exposure to both accelerated aging and ionizing radiation, as do the density (3.63 ± 0.02 g/cm3) radiopacity (7049 ± 847HU), chemical composition and XRD diffractograms for each glass. Therefore it can be concluded that the accelerated aging conditions tested herein or use of 30 kGy γ-irradiation dose or subsequent effects does not affect the local environment of the 29Si isotope in the glasses, nor does it significantly alter the XRD diffraction patterns, chemical composition, Tg, density or the radiopacity values for the glass composition (0.562Si–0.035Ca–0.188Zn–0.068La–0.042Ti–0.035 Mg–0.035Sr–0.035Na) described in this work.
    No preview · Article · Oct 2014 · Journal of Non-Crystalline Solids
  • M. S. Hasan · S Kehoe · D Boyd
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    ABSTRACT: Embolization of vascular tumors is an important tool in minimally invasive surgical intervention. Radiopaque, non-degradable, and non-deformable spherical zinc–silicate glass particles were produced in a range of 45–500 μm. Three size ranges (45–150, 150–300, and 300–500 μm) were used in the current study. The glass microspheres were eluted in polar (saline solution) and non-polar (dimethyl sulfoxide) medium, and ion release profiles were recorded using inductively coupled plasma atomic emission spectroscopy. Approximately 80% of Gaussian distribution was achieved by simple sieving. The ions released from the microspheres were dependent upon surface area to volume ratio as well as the nature of elution media. Greater ions were released from smaller particles (45–150 μm) having largest surface area in polar medium. For the genotoxicity bacterial mutation Ames assay, the concentrations of all the ions were well below their therapeutic concentration reported in the literature. No mutagenic effect was observed in the bacterial mutation Ames test. Hence, it can be concluded that the glass microspheres produced herein are non-mutagenic further supporting the materials potential as a suitable embolic agent.
    No preview · Article · Sep 2014 · Journal of Biomaterials Applications
  • Lauren Kiri · Daniel Boyd

    No preview · Conference Paper · Aug 2014

Publication Stats

791 Citations
145.63 Total Impact Points


  • 2010-2016
    • Dalhousie University
      • • Faculty of Dentistry
      • • School of Biomedical Engineering
      Halifax, Nova Scotia, Canada
  • 2015
    • Halifax Biomedical Inc.
      Halifax, Nova Scotia, Canada
  • 2009
    • Cork Institute of Technology
      Corcaigh, Munster, Ireland
  • 2004-2009
    • University of Limerick
      • Materials and Surface Science Institute (MSSI)
      Luimneach, Munster, Ireland