A R Boyd

University of Ulster, Antrim, NIR, United Kingdom

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Publications (26)58.47 Total impact

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    ABSTRACT: First attempt to sputter strontium substituted hydroxyapatite thin films using RF magnetron co-deposition•Strontium content of coatings is influenced by the target composition and configuration.•Increased preferred orientation (002) with increasing strontium content within the coatings•Strontium content of the coatings influences the coating morphology.
    Materials Science and Engineering: C. 01/2015; 46.
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    ABSTRACT: The nature of the initial interaction between calcium phosphate (Ca-P) thin films and osteoblasts can be influenced by a number of different properties including the phase, crystallinity, stoichiometry and composition of the surface. There is still a strong interest in developing and studying Ca-P surfaces that have the ability to accurately control the osteoblast response. Radio frequency (RF) magnetron sputtering is a technique that allows for accurate control of the properties of deposited Ca-P coatings and has been studied extensively because of this fact. In this work, Ca-P coatings were co-deposited using RF magnetron sputtering in order to study the effect of changing the target stoichiometry on the initial in vitro behavior of MG63 osteoblast-like cells. The samples produced were analysed both as-deposited and after thermal annealing to 500 °C. After annealing XPS analyses of the samples co-deposited using tricalcium phosphate (TCP) materials gave a Ca/P ratio of 1.71 ± 0.01, as compared to those co-deposited from hydroxyapatite (HA) materials, with a Ca/P of 1.82 ± 0.06. In addition to this, the curve fitted XPS data indicated the presence of low levels of carbonate in the coatings. Despite this the XRD results for all of the annealed coatings were shown to be characteristic of pure HA with a preferred 002 orientation. The atomic force microscopy results also highlighted that both types of coatings had surface features of a similar size (200-220 nm). Both surfaces exhibited a degree of surface degradation, even after 1 h of cell culture. However, the TCP derived surfaces showed an enhanced osteoblastic cell response in terms of cell adhesion and cell proliferation in the earlier stages of cell culture than the surfaces deposited from HA. An improvement in the initial cell attachment and a potential for increased cell proliferation rates is viewed as a highly advantageous result in relation to controlling the osteoblast response on these surfaces.
    Journal of Materials Science Materials in Medicine 08/2013; · 2.14 Impact Factor
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    ABSTRACT: Calcium phosphate (CaP) coatings are of continuing significant interest due to their ability to directly promote bone cell differentiation. Whereas sputter deposited CaP coatings have much to offer in this regard, in the as-deposited state they are inherently amorphous and readily undergo rapid dissolution. This behaviour severely limits their ability to support bone cell adhesion and the subsequent events of proliferation and/or differentiation without subsequent processing such as thermal annealing. Removal of the need for this additional processing step would significantly increase their utility. This paper reports a study of the use of nano-porous titania substrates to directly control the rate of dissolution of thin amorphous as-deposited CaP sputter coatings. Titania nanotubes with different pore sizes were prepared by electrochemical anodization of titanium foils and sputter coated with CaP. Dissolution studies were performed on the as-deposited CaP layers in cell culture media for periods of up to 21 days. Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) analysis confirmed the potential of the nanotubes to prolong the rate of loss of CaP over the entire 21 day period as compared to coatings prepared on flat polished titanium surfaces, which dissolved completely in less than 48 h. The CaP coated titania nanotube surfaces showed high levels of osteoblast attachment and proliferation with no signs of cell death. Alkaline phosphatase (ALP) activity measurements at 21 days indicated that the highest levels of osteoblast differentiation occurred on CaP thin films deposited onto titania nanotubes with an average pore size of 30 ¡ 7.5 nm and tube length of 1.3 ¡ 0.2 mm. These results indicate that prolonged availability of the as-deposited sputtered CaP can be provided for by use of a substrate surface comprising titania nanotubes. Moreover, nanotube pore size and tube length affect the rate of CaP dissolution and attendant cell behaviour thereon.
    RSC Advances 04/2013; 3:11263–11273. · 3.71 Impact Factor
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    ABSTRACT: Raman spectroscopy is employed to determine the suitability of the U20S osteoblast-like cell line for use as a model for human primary osteoblasts, with emphasis on the ability of these cell types to replicate their tissue of origin. It was found that both cell types demonstrated early stage mineral deposition that followed significantly different growth patterns. Analysis of the growth pattern and spectral data from primary cells revealed increasing bone quality ratios and a high crystallinity, consistent with previous reports. Conversely the investigation of the U20S osteoblast-like cell line provided evidence of dense multilayered mineralised regions that corresponded more closely to native bone in terms of its crystallinity and bone quality ratios. This finding contradicts previous reports on U20S osteoblast-like cells which have consistently described them as non-osteoinductive when cultured in various conditions on a number of substrates. This work demonstrates the successful application of Raman spectroscopy combined with biological and multivariate analysis for the investigation of osteoblast-like U20S cells and human primary osteoblasts, specifically with focus on the osteoinductive ability of the osteoblast-like cell line and the comparative differences in relation to the primary osteoblasts.
    The Analyst 03/2012; 137(7):1559-69. · 4.23 Impact Factor
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    ABSTRACT: Being able to control the behaviour of osteoblast-like cells on a surface may provide a genuine insight into the material surface characteristics and help in creating a successful coating/cell interface. The possibility of creating a micro-environment that can induce proliferation, differentiation and mineralisation of bone cells in vitro, by successfully combining both chemistry and topography of a micro-fabricated substrate is an area that requires a multi-disciplinary approach. Utilising sputter deposition, a process that lends itself to high processability, in conjunction with photolithography allowing for the creation of highly repeatable etched surfaces, we aim to provide a successful combination of chemistry and topography. Correlating the substrate conditions with resultant osteoblast biological function and activity can ultimately be used with a view to modulating the behavior of osteoblast-like cells in vitro.
    Journal of Materials Science Materials in Medicine 01/2012; 23(3):835-51. · 2.14 Impact Factor
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    Journal of Materials Science Materials in Medicine 08/2011; 22(8):1931. · 2.14 Impact Factor
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    ABSTRACT: The differentiation of stem cells into multi-lineages is essential to aid the development of tissue engineered materials that replicate the functionality of their tissue of origin. For this study, Raman spectroscopy was used to monitor the formation of a bone-like apatite mineral during the differentiation of human mesenchymal stem cells (hMSCs) towards an osteogenic lineage. Raman spectroscopy observed dramatic changes in the region dominated by the stretching of phosphate groups (950-970 cm(-1)) during the period of 7-28 days. Changes were also seen at 1030 cm(-1) and 1070 cm(-1), which are associated with the P-O symmetric stretch of PO(4)(3-) and the C-O vibration in the plane stretch of CO(3)(2-). Multivariate factor analysis revealed the presence of various mineral species throughout the 28 day culture period. Bone mineral formation was observed first at day 14 and was identified as a crystalline, non-substituted apatite. During the later stages of culture, different mineral species were observed, namely an amorphous apatite and a carbonate, substituted apatite, all of which are known to be Raman markers for a bone-like material. Band area ratios revealed that both the carbonate-to-phosphate and mineral-to-matrix ratios increased with age. When taken together, these findings suggest that the osteogenic differentiation of hMSCs at early stages resembles endochondral ossification. Due to the various mineral species observed, namely a disordered amorphous apatite, a B-type carbonate-substituted apatite and a crystalline non-substituted hydroxyapatite, it is suggested that the bone-like mineral observed here can be compared to native bone. This work demonstrates the successful application of Raman spectroscopy combined with biological and multivariate analyses for monitoring the various mineral species, degree of mineralisation and the crystallinity of hMSCs as they differentiate into osteoblasts.
    The Analyst 06/2011; 136(12):2471-81. · 4.23 Impact Factor
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    ABSTRACT: There are many techniques that allow in vitro interactions among cells and their environment to be monitored, including molecular, biochemical and immunochemical techniques. Traditional techniques for the analysis of cells often require fixation or lysis from substrates; however, use of such destructive methods is not feasible where the expanded cell cultures are required to be used for clinical implantation. Several studies have previously highlighted the potential of Raman spectroscopy to provide useful information on key biochemical markers within cells. As such, we highlight the capability of Raman spectroscopy with different laser spot sizes for use as a non-invasive, rapid, and specific method to perform in situ analysis of primary bovine aortic endothelial cells (BAECs). Raman spectra were collected from both individual live cells cultured on fused silica substrates and on clusters of live cells placed on fused silica substrates, measured at 532 and 785 nm. The results obtained show notable spectral differences in DNA/RNA region indicative of the relative cytoplasm and nucleus contributions. Raman spectra of cell clusters show slight variations in the intensity of the phenylalanine peak (1004 cm(-1)) indicating variations in protein contribution. These spectra also highlight contributions from other cellular components such as, proteins, lipids, nucleic acids and carbohydrates, respectively.
    Journal of Materials Science Materials in Medicine 06/2011; 22(8):1923-30. · 2.14 Impact Factor
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    ABSTRACT: Protein adsorption onto calcium phosphate (Ca-P) bioceramics utilised in hard tissue implant applications has been highlighted as one of the key events that influences the subsequent biological response, in vivo. This work reports on the use of surface-matrix assisted laser desorption ionisation mass spectrometry (Surface-MALDI-MS) as a technique for the direct detection of foetal bovine serum (FBS) proteins adsorbed to hybrid calcium phosphate/titanium dioxide surfaces produced by a novel radio frequency (RF) magnetron sputtering method incorporating in situ annealing between 500°C and 700°C during deposition. XRD and XPS analysis indicated that the coatings produced at 700°C were hybrid in nature, with the presence of Ca-P and titanium dioxide clearly observed in the outer surface layer. In addition to this, the Ca/P ratio was seen to increase with increasing annealing temperature, with values of between 2.0 and 2.26 obtained for the 700°C samples. After exposure to FBS solution, surface-MALDI-MS indicated that there were significant differences in the protein patterns as shown by unique peaks detected at masses below 23.1 kDa for the different surfaces. These adsorbates were assigned to a combination of growth factors and lipoproteins present in serum. From the data obtained here it is evident that surface-MALDI-MS has significant utility as a tool for studying the dynamic nature of protein adsorption onto the surfaces of bioceramic coatings, which most likely plays a significant role in subsequent bioactivity of the materials.
    Journal of Materials Science Materials in Medicine 01/2011; 22(1):71-84. · 2.14 Impact Factor
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    ABSTRACT: Each year, NIBES hosts a spring conference that is jointly organised by Queen's University of Belfast and University of Ulster. The 29th NIBES Spring meeting took place on 8th April 2009 at Queen's University of Belfast. NIBES 2009 had an impressive scientific program with two international leading plenary speakers and 28 oral presentations.
    Journal of Materials Science Materials in Medicine 08/2010; 21(8):2253-4. · 2.14 Impact Factor
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    ABSTRACT: The ability to engineer biomaterial surfaces that are capable of a dynamic interaction with cells and tissues is central to the development of medical implants with improved functionality. An important consideration in this regard is the role played by the extracellular proteins that bind to an implant surface in vivo. Deliberate use of an ad-layer of such proteins on an implant surface has been observed to guide and direct cell response. However, the role that changes in surface topography might play in determining the nature of this cell-protein-surface interaction has not been investigated in detail. In this study, calcium phosphate (CaP) thin films have been deposited onto substrates with varying topography such that this is reflected in the (conformal) CaP surface features. A fibronectin (FN) ad-layer was then deposited from solution onto each surface and the response of MG63 osteoblast-like cells investigated. The results revealed that in all cases, the presence of the adsorbed FN layer on the CaP thin films improved MG63 cell adhesion, proliferation and promoted early onset differentiation. Moreover, the nature and scale of the response were shown to be influenced by the underlying CaP surface topography. Specifically, MG63 cell on FN-coated CaP thin films with regular topographical features in the nanometer range showed statistically significant differences in focal adhesion assembly, osteocalcin expression and alkaline phosphase activity compared to CaP thin films that lacked these topographical features. As such, these data indicate that surface topography can be used to further influence cell adhesion and downstream differentiation by enhancing the effects of a surface adsorbed FN layer.
    Colloids and surfaces B: Biointerfaces 03/2010; 78(2):283-90. · 4.28 Impact Factor
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    A R Boyd, G A Burke, B J Meenan
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    ABSTRACT: Raman spectroscopy has been used to determine the chemical composition of materials for over 70 years. Recent spectacular advances in laser and CCD camera technology creating instruments with higher sensitivity and lower cost have initiated a strong resurgence in the technique, ranging from fundamental research to process control methodology. One such area of increased potential is in tissue engineering and regenerative medicine (TERM), where autologous cell culture, stem cell biology and growth of human cells on biomaterial scaffolds are of high importance. Traditional techniques for the in vitro analysis of biochemical cell processes involves cell techniques such as fixation, lysis or the use of radioactive or chemical labels which are time consuming and can involve the perpetuation of artefacts. Several studies have already shown the potential of Raman spectroscopy to provide useful information on key biochemical markers within cells, however, many of these studies have utilised micro- or confocal Raman to do this, which are not suited to the rapid and non-invasive monitoring of cells. For this study a versatile fit-for-purpose Raman spectrometer was used, employing a macro-sampling optical platform (laser spot size 100 mum at focus on the sample) to discriminate between different TERM relevant cell types and viable and non-viable cells. The results clearly show that the technique is capable of obtaining Raman spectra from live cells in a non-destructive, rapid and non-invasive manner, however, in these experiments it was not possible to discriminate between different cell lines. Despite this, notable differences were observed in the spectra obtained from viable and non-viable cells, showing significant changes in the spectral profiles of protein, DNA/RNA and lipid cell constituents after cell death. It is evident that the method employed here shows significant potential for further utilisation in TERM, providing data directly from live cells that fits within a quality assurance framework and provides the opportunity to analyse cells in a non-destructive manner.
    Journal of Materials Science Materials in Medicine 12/2009; 21(8):2317-24. · 2.14 Impact Factor
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    ABSTRACT: The role of roughening and functionalization processes involved in modifying the wettability of poly(epsilon-caprolactone) (PCL) after treatment by an atmospheric pressure glow discharge plasma is discussed. The change in the ratio of CO/C-O bonds is a significant factor influencing the wettability of PCL. As the contact angle decreases, the level of CO bonds tends to rise. Surface roughness alterations are the driving force for lasting increases in wettability, while the surface functional species are shorter lived. We can approximate from ageing that the increase in wettability for PCL after plasma treatment is 55-60% due to roughening and 40-45% due to surface functionalization for the plasma device investigated.
    Acta biomaterialia 03/2009; 5(6):2025-32. · 5.68 Impact Factor
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    ABSTRACT: A range of calcium phosphate (Ca–P) coatings have been sputter deposited at low deposition power from Ca–P targets with different phase compositions. The resultant surfaces were analysed both before and after post-deposition annealing (PDA) using X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR) and X-ray Photoelectron Spectroscopy (XPS). The as-deposited surfaces were found to be amorphous in nature and had Ca/P ratios lower than that for their precursor target materials. After PDA at 500 °C, the FTIR and XRD data indicated that the coatings were all hydroxyapatite (HA) in nature. However, the Ca/P ratios were seen to increase significantly, with values above that of their starting precursor target material. It is evident that the Ca/P ratio of the different surfaces, both before and after PDA, are dependent upon the phase composition and stoichiometry of target material. This study has shown the utility of varying the precursor target material in order to modify the resultant surface conditions.
    Surface & Coatings Technology - SURF COAT TECH. 09/2008; 203(1).
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    ABSTRACT: The role of titanium dioxide (TiO2) as a means to engender enhanced stability into calcium phosphate (Ca-P) coatings has been well recognised. Several different methods have been used to create such Ca-P/TiO2 hybrid layers on a range of substrates. This paper reports the properties of a Ca-P/TiO2 system created by the sputter deposition of hydroxyapatite onto a titanium surface and the subsequent thermal diffusion of TiO2 through the porous Ca-P layer. The role of temperature in determining the surface contribution from TiO2 has been determined. Coatings annealed up to 600 degrees C did not exhibit any hybrid nature in the uppermost surface, however the coatings annealed to 700 degrees C did show the presence of both HA and rutile TiO2. The surfaces annealed to 800 degrees C were predominantly rutile TiO2. It was also observed that the Ca/P ratio decreased with increasing annealing temperature and that the coating annealed to 700 degrees C had a value of 1.82 +/- 0.07, which was closest to stoichiometric HA. Furthermore, the coatings that were annealed to 700 degrees C displayed a Ca-P/TiO2 hybrid nature, specifically in their uppermost surface and supported the growth and proliferation of osteoblast-like cells more readily when compared to the HA coatings or the rutile TiO2 surfaces.
    Journal of Materials Science Materials in Medicine 03/2008; 19(2):485-98. · 2.14 Impact Factor
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    ABSTRACT: Fibronectin (FN) adsorption to Calcium Phosphate (CaP) thin film surfaces with topographical features in the submicron to nanometre range has been investigated. CaP thin films have been produced by Radio-Frequency (RF) magnetron sputter deposition and a sputtered Titanium (Ti) interlayer was used to create substrates with nanoscale surface features. Detailed X-ray Photoelectron Spectroscopy (XPS) analysis of the FN ad-layers indicated differences in the nature of the adsorption on the main surface types. Binding studies revealed that the FN had a stronger affinity for the CaP on sputtered Ti. These data suggest that nanoscale topography can influence FN adsorption on CaP thin film surfaces.
    International Journal of Nano and Biomaterials 01/2008; 1(3).
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    ABSTRACT: The application of either hydroxyapatite (HA) or titanium dioxide (TiO 2) as coatings onto existing bioinert materials has been explored as the key route for enhancing the surface properties of hard tissue implant devices. However, it has been proposed that composite HA/TiO 2 coatings may provide significant advantages for the application of such surfaces. This work reports on the surface properties of such composite HA/TiO 2 surfaces produced by the sputter deposition of HA onto a titanium surface and their subsequent thermal processing using either post deposition (PDA) or in situ annealing (ISA). For both the PDA and ISA coatings, a hybrid nature was only achieved in the uppermost surface region after annealing at 700 °C. It was observed that the Ca/P ratio decreased with increasing annealing temperature for the PDA coatings and that the coating annealed to 700 °C had a value of 1.82 ± 0.07, which was closest to stoichiometric HA. In comparison, the Ca/P ratio of the ISA samples increased with increasing annealing temperature. It has been shown that the resultant coatings have surface properties that are dependent on the annealing profiles employed, and that a temperature of 700 °C is required in order to create a Ca–P/TiO 2 hybrid surface.
    Materials Science and Engineering: C. 02/2007; 28(2).
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    ABSTRACT: A series of Ca P coatings have been co-deposited by RF magnetron sputtering from hydroxyapatite targets at a range of different argon gas pressures (1 5 Pa) at a low discharge power level. The resultant surfaces were analysed both as-deposited and after annealing at 500 °C using fourier transform infrared spectroscopy (FTIR), X-Ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and stylus profilometry. The deposition rate increased with increasing argon gas pressure up to 2 Pa, but decreased significantly as the pressure increased up to 5 Pa. The Ca/P ratios of the as-deposited coatings were lower than expected, and decreased significantly at the higher argon gas pressures. The corresponding FTIR and XRD data showed that the as-deposited surfaces were poorly hydroxylated and were mostly amorphous in nature. By comparison, the annealed surfaces had Ca/P ratios of between 3.38 ± 0.11 (1 Pa) and 1.82 ± 0.06 (5 Pa). The FTIR and XRD data for the annealed samples were indicative of HA, however, as the gas pressure increased above 3 Pa, these surfaces were most likely transformed into dehydroxylated HA. This study has shown the utility of varying the argon gas pressure whilst co-sputtering HA in order to modify the resultant surface conditions.
    Nuclear Instruments and Methods in Physics Research Section B Beam Interactions with Materials and Atoms 01/2007; 258:421-428. · 1.19 Impact Factor
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    A R Boyd, B J Meenan, N S Leyland
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    ABSTRACT: The initial behaviour and ultimately the long-term performance of calcium phosphate (Ca–P) coatings for hard tissue implant applications are influenced by their dissolution properties. For this study, Ca–P coatings were deposited onto Ti-6Al-4V substrates using RF magnetron sputtering. The physico-chemical nature of these deposited layers was then determined both before and after annealing at 400 °C using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Furthermore, their dissolution behaviour in phosphate buffered saline (PBS) solution was also examined using similar techniques. The data shows clearly that the as-deposited coatings are amorphous when compared with the more crystalline coatings produced after annealing at 400 °C. These as-deposited coatings completely dissolve after exposure to the PBS for only 24 h; however, the dissolution rate of the annealed coatings is more restrained. Whereas the XPS and FTIR data show no change in the chemical nature of the annealed coatings after 30 days, the AFM results reveal subtle changes in the surface topography of the coatings after only 1 h of immersion. These data clearly show the utility of surface analytical techniques, such as AFM in combination with more established techniques for examining the surface properties of Ca–P coatings. Furthermore, the study also shows that calcium phosphate coatings deposited at low power using RF magnetron sputtering can undergo a decreased dissolution rate under physiological conditions they when subjected to post deposition annealing.
    Surface & Coatings Technology - SURF COAT TECH. 12/2005; 200(20).
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    ABSTRACT: Poly-L-lactide (PLLA) is one of the most significant members of a group of polymers regarded as bioabsorbable. Degradation of PLLA proceeds through hydrolysis of the ester bonds in the polymer chains and is influenced significantly by the polymer's molecular weight and crystallinity. To evaluate the effects of processing and sterilisation on these properties, PLLA pellets were either compression moulded or extruded, subjected to annealing at 120 degrees C for 4h and sterilised by ethylene oxide (EtO) gas. Procedures were used to evaluate the mechanical properties, molecular weight and crystallinity. Upon processing, the crystallinity of the material fell from 61% for the PLLA pellets to 12% and 20% for the compressed and extruded components, respectively. After annealing, crystallinity increased to 43% for the compression-moulded material and 40% for the extruded material. Crystallinity further increased upon EtO sterilisation. A slight decrease in molecular weight was observed for the extruded material through processing, annealing and sterilisation. Young's modulus generally increased with increasing crystallinity, and extension at break and tensile strength decreased. The results from this investigation suggest that PLLA is sensitive to processing and sterilisation, altering properties critical to its degradation rate.
    Biomaterials 09/2004; 25(18):3939-49. · 8.31 Impact Factor