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Abstract Isomeric o,m,p-polyphenylenes were prepared by oxidation-cationic polymeriation of biphenyl with various proportions of the polymerization components biphenyl-AlCl3-Cu-Cl2. The insoluble fraction in chlorobenzene was separated.... more
Abstract Isomeric o,m,p-polyphenylenes were prepared by oxidation-cationic polymeriation of biphenyl with various proportions of the polymerization components biphenyl-AlCl3-Cu-Cl2. The insoluble fraction in chlorobenzene was separated. The insoluble polyphenylenes were then doped with anhydrous FeCl3, AlCl3, and SnCl4 in solutions of acetonitrile (ACN), nitrobenzene (N), and acetone (A). X-ray diffraction, Fourier Transform Infrared Spectroscopy (FTIR), and electrical conductivity measurements were carried out to characterize the undoped and doped materials. Some of the o,m,p-polyphenylenes had semiconductive properties after doping depending on the proportion of biphenyl-AlCl3-CuCl2 and the doping system (dopant and solvent).
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The surface characteristics of several natural fibers—flax, hemp and cellulose— were investigated using scanning electron microscopy, BET-surface area and zeta (-) potential measurements. -Potential measurements using the streaming... more
The surface characteristics of several natural fibers—flax, hemp and cellulose— were investigated using scanning electron microscopy, BET-surface area and zeta (-) potential measurements. -Potential measurements using the streaming poten-tial method were performed in order to study the water uptake behavior as well as the surface properties of several natural fibers. The influence of different flax-fiber separation methods and several modifications, like industrial purification, and such a treatment followed by alkaline purification as well as polypropylene grafting on the fiber surface morphology, surface area and time- and pH-depending -poten-tials were studied. The time-dependence of the -potential, measured in 1 mM KCl solution, offers an alternative possibility to estimate the water uptake behavior for nearly all investigated natural fibers. The water uptake data derived from the -po-tential measurements ( f (t)) were compared with data from conventional water adsorption studie...
Materials such as biocompatible metals, ceramics, composites, and polymers are used in the fabrication of biomedical implants which are used in the human body especially for the replacement of hard tissues. However, they degrade with time... more
Materials such as biocompatible metals, ceramics, composites, and polymers are used in the fabrication of biomedical implants which are used in the human body especially for the replacement of hard tissues. However, they degrade with time since they are subjected to different mechanical conditions and long-term exposure to fluids corrosion. Therefore, to curb these limitations, the surface properties are usually coated with thin metallic and nonmetallic materials. One such nonmetal is Hydroxyapatite (HA) coating which has the potential of mitigating these shortcomings and it is a biocompatible and bioactive material. This paper provides an overview of the existing literature on the sputtering of hydroxyapatite coating for biomedical applications with emphasis on the deposition conditions and parameters.
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Active screen plasma nitriding (ASPN) is used to chemically modify the surface of UHMWPE. This is an unexplored and new area of research. ASPN allows the homogeneous treatment of any shape or surface at low temperature; therefore, it was... more
Active screen plasma nitriding (ASPN) is used to chemically modify the surface of UHMWPE. This is an unexplored and new area of research. ASPN allows the homogeneous treatment of any shape or surface at low temperature; therefore, it was thought that ASPN would be an effective technique to modify organic polymer surfaces. ASPN experiments were carried out at 120 °C using a dc plasma nitriding unit with a 25% N(2) and 75% H(2) atmosphere at 2.5 mbar of pressure. UHMWPE samples treated for different time periods were characterized by nanoindentation, FTIR, XPS, interferometry and SEM. A 3T3 fibroblast cell line was used for in vitro cell culture experiments. Nanoindentation of UHMWPE showed that hardness and elastic modulus increased with ASPN treatment compared to the untreated material. FTIR spectra did not show significant differences between the untreated and treated samples; however, some changes were observed at 30 min of treatment in the range of 1500-1700 cm(-1) associated mainly with the presence of N-H groups. XPS studies showed that nitrogen was present on the surface and its amount increased with treatment time. Interferometry showed that no significant changes were observed on the surfaces after the treatment. Finally, cell culture experiments and SEM showed that fibroblasts attached and proliferated to a greater extent on the plasma-treated surfaces leading to the conclusion that ASPN surface treatment can potentially significantly improve the biocompatibility behaviour of polymeric materials
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We report the growth of ultrathin diamond nanorods (DNRs) by a microwave plasma assisted chemical vapor deposition method using a mixture gas of nitrogen and methane. DNRs have a diameter as thin as 2.1 nm, which is not only smaller than... more
We report the growth of ultrathin diamond nanorods (DNRs) by a microwave plasma assisted chemical vapor deposition method using a mixture gas of nitrogen and methane. DNRs have a diameter as thin as 2.1 nm, which is not only smaller than reported one-dimensional diamond nanostructures (4�300 nm) but also smaller than the theoretical value for energetically stable DNRs. The ultrathin DNR is encapsulated in tapered carbon nanotubes (CNTs) with an orientation relation of (111)diamond//(0002)graphite. Together with diamond nanoclusters and multilayer graphene nanowires/nano-onions, DNRs are self-assembled into isolated electronemitting spherules and exhibit a low-threshold, high current-density (flat panel display threshold: 10 mA/cm2 at 2.9 V/�m) field emission performance, better than that of all other conventional (Mo and Si tips, etc.) and popular nanostructural (ZnO nanostructure and nanodiamond, etc.) field emitters except for oriented CNTs. The forming mechanism of DNRs is sugges...
Abstract Ceramics long history in biomedical field is related to their high biocompatibility and mechanical properties. Precisely, for joint replacements, wear resistance is fundamental, so advanced ceramics as alumina and zirconia are... more
Abstract Ceramics long history in biomedical field is related to their high biocompatibility and mechanical properties. Precisely, for joint replacements, wear resistance is fundamental, so advanced ceramics as alumina and zirconia are preferred. Developments in ceramic additive manufacturing allow for dense ceramic parts with improved mechanical properties and shape accuracy. This paper focuses on the tribological analysis of stereolithography-manufactured components for orthopaedics. Alumina, yttria-stabilised zirconia, 10 and 20 wt% zirconia toughened alumina (ZTA) samples were analysed. The effect of surface finishing, microstructure and microhardness on wear was considered. Printing orientation does not significantly impact microhardness, wettability, and microporosity. However, some printing artefacts as the staircase effect were observed on spherical surfaces. Zirconia system presented high wear rates and friction coefficient, while alumina system showed more acceptable and stable values, with the formation of a self-mated tribofilm. ZTA composites presented the lowest wear volume and better mechanical and surface properties in general.
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Research Interests: Materials Science, Biomedical Engineering, Cell Adhesion, Nanotechnology, Medicine, and 15 moreCell Culture, Biocompatibility, Cell line, Biomedical Materials, Medical Biotechnology, Mice, Animals, Nitrogen, Hardness, Plasma nitriding, Elastic Modulus, Materials Testing, Biocompatible Materials, fibroblasts, and Cell culture techniques
Educational experts partnered with engineering experts to identify thresholds in learning in level 4 engineering and materials classes at Oxford. Threshold concepts is a term used by educationalists to describe particular ideas within... more
Educational experts partnered with engineering experts to identify thresholds in learning in level 4 engineering and materials classes at Oxford. Threshold concepts is a term used by educationalists to describe particular ideas within disciplines that open up new ways of thinking, allowing students to progress in that discipline. Threshold concepts are transformative for students insofar as they change the way that students perceive the field. Often thresholds are particularly troublesome or tricky for students. 14 tutors and eight students were interviewed to: a) identify perceived thresholds, b) explore why and how proposed thresholds were troublesome, transformative and integrative, and 3) discuss their experience of teaching or learning them. The integrative function of Oxford’s tutorials gave tutors insight into the integrative and transformative dimensions of potential thresholds. They emphasised discipline-specific thinking processes that evolve over time, including connectin...
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Human skeletal bone loss is a major health concern in the twenty-first century, with massive socioeconomic implications. The objective of the current work is to develop and characterize bioactive tellurite glasses for biomedical... more
Human skeletal bone loss is a major health concern in the twenty-first century, with massive socioeconomic implications. The objective of the current work is to develop and characterize bioactive tellurite glasses for biomedical applications. As so, tellurium oxide- (TeO2) and lanthanide (Ln3+)-doped borate host systems have been developed and incorporated in a hydroxyapatite (HA) matrix, being adequately characterized regarding solid-state parameters and for in vitro biological response. In the proposed work, the following scientific questions will be addressed: Will the reported tellurite-lanthanide (Te-Ln3+) host glass-reinforced hydroxyapatite (HA) ceramic materials influence the cell behavior, such as proliferation and differentiation? Does this Te-Ln material show any luminescence response? Further, the research on lanthanide-based materials is promising, with potential application in prospective medical applications. Consequently, investigation into the role of Te-Ln3+-HA hos...
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The interface between implanted devices and their host tissue is complex and is often optimized for maximal integration and cell adhesion. However, this also gives a surface suitable for bacterial colonization. We have developed a novel... more
The interface between implanted devices and their host tissue is complex and is often optimized for maximal integration and cell adhesion. However, this also gives a surface suitable for bacterial colonization. We have developed a novel method of modifying the surface at the material–tissue interface with an antimicrobial peptide (AMP) coating to allow cell attachment while inhibiting bacterial colonization. The technology reported here is a dual AMP coating. The dual coating consists of AMPs covalently bonded to the hydroxyapatite surface, followed by deposition of electrostatically bound AMPs. The dual approach gives an efficacious coating which is stable for over 12 months and can prevent colonization of the surface by both Gram-positive and Gram-negative bacteria.
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Titanium (Ti) and titanium alloys (Ti6Al4V) are both used in clinical areas for example in orthopaedics, craniofacial, dental and bone replacement due to their exceptional mechanical properties tensile strength, stiffness, fracture... more
Titanium (Ti) and titanium alloys (Ti6Al4V) are both used in clinical areas for example in orthopaedics, craniofacial, dental and bone replacement due to their exceptional mechanical properties tensile strength, stiffness, fracture toughness and corrosion resistance. The titanium oxide layer plays an important role on the surface of Ti allowing deposition of biomaterials, cells, proteins and peptides. Some studies suggested that a second bioactive material should be deposited, sprayed or attracted to the surface of Ti in order to increase its bioactivity. A well-known material for its high bioactivity is hydroxyapatite (HA)4 and is widely used as coating on implant surfaces. The aim of this project is to increase the interaction of nano hydroxyapatite and titanium oxide using an organic interphase of peptides known as aptamers.
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Titanium (Ti) and titanium alloys (Ti6Al4V) are both used in clinical areas for example in orthopaedics, craniofacial, dental and bone replacement due to their exceptional mechanical properties tensile strength, stiffness, fracture... more
Titanium (Ti) and titanium alloys (Ti6Al4V) are both used in clinical areas for example in orthopaedics, craniofacial, dental and bone replacement due to their exceptional mechanical properties tensile strength, stiffness, fracture toughness and corrosion resistance. The titanium oxide layer plays an important role on the surface of Ti allowing deposition of biomaterials, cells, proteins and peptides. Some studies suggested that a second bioactive material should be deposited, sprayed or attracted to the surface of Ti in order to increase its bioactivity. A well-known material for its high bioactivity is hydroxyapatite (HA) and is widely used as coating on implant surfaces. The aim of this project is to increase the interaction of nano hydroxyapatite and titanium oxide using an organic interphase of peptides known as aptamers.
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Infections are common complications in joint replacement surgeries. Eradicated infections can lead to implant failure. In this paper, analogues of the peptide KR-12 derived from the human cathelicidin LL-37 were designed, synthesised, and... more
Infections are common complications in joint replacement surgeries. Eradicated infections can lead to implant failure. In this paper, analogues of the peptide KR-12 derived from the human cathelicidin LL-37 were designed, synthesised, and characterised. The designed antimicrobial peptides (AMPs) were attached to the surface of a titanium alloy, Ti6Al4V, by conjugation to a polydopamine linking substrate. The topography of the polydopamine coating was evaluated by electron microscopy and coating thickness measurements were performed with ellipsometry and Atomic Force Microscopy (AFM). The subsequently attached peptide stability was investigated with release profile studies in simulated body fluid, using both fluorescence imaging and High-Performance Liquid Chromatography (HPLC). Finally, the hydrophobicity of the coating was characterised by water contact angle measurements. The designed AMPs were shown to provide long-term bonding to the polydopamine-coated Ti6Al4V surfaces.
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Most marine biomaterials comprise of inorganic crystals with various tectonic structures that permit the inclusion, storage, release, and delivery of organic biomolecules. One analog with those functions is exploited for preclinical... more
Most marine biomaterials comprise of inorganic crystals with various tectonic structures that permit the inclusion, storage, release, and delivery of organic biomolecules. One analog with those functions is exploited for preclinical application.
The surface of a medical implant is required to interact favourably with ions, biomolecules and cells in vivo, commonly resulting in the formation of the extracellular matrix.
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Glass ionomer cement (GIC) represents a major transformation in restorative dentistry. Wear of dental restoratives is a common phenomenon and the determination of the wear resistance of direct-restorative materials is a challenging task.... more
Glass ionomer cement (GIC) represents a major transformation in restorative dentistry. Wear of dental restoratives is a common phenomenon and the determination of the wear resistance of direct-restorative materials is a challenging task. The aim of this paper was to evaluate the wear resistance of novel glass ionomer cement by two wear-test methods and to compare the two wear methods.The wear resistance of a conventional glass ionomer cement (HiFi Advanced Health Care Kent, UK) and cements modified by including various percentages of nanoclays (1, 2 and 4 wt %) was measured by a reciprocating wear test (ball-on-flat) and Oregon Health and Sciences University's (OHSU) wear simulator. The OHSU wear simulation subjected the cement specimens to three wear mechanisms, namely abrasion, three-body abrasion and attrition using a steatite antagonist. The abrasion wear resulted in material loss from GIC specimen as the steatite antagonist forced through the exposed glass particles when it...
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The interface between implanted devices and their host tissue is complex and is often optimized for maximal integration and cell adhesion. However, this also gives a surface suitable for bacterial colonization. We have developed a novel... more
The interface between implanted devices and their host tissue is complex and is often optimized for maximal integration and cell adhesion. However, this also gives a surface suitable for bacterial colonization. We have developed a novel method of modifying the surface at the material-tissue interface with an antimicrobial peptide (AMP) coating to allow cell attachment while inhibiting bacterial colonization. The technology reported here is a dual AMP coating. The dual coating consists of AMPs covalently bonded to the hydroxyapatite surface, followed by deposition of electrostatically bound AMPs. The dual approach gives an efficacious coating which is stable for over 12 months and can prevent colonization of the surface by both Gram-positive and Gram-negative bacteria.
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The aim of this study is to characterise a range of model and commercially available glasses used to form glass (ionomer) polyalkenoate cements. A range of model fluoro-alumino-silicate glasses that form the basis of glass (ionomer)... more
The aim of this study is to characterise a range of model and commercially available glasses used to form glass (ionomer) polyalkenoate cements. A range of model fluoro-alumino-silicate glasses that form the basis of glass (ionomer) polyalkenoate cements and five commercial glasses have been characterised by 29Si, 27Al, 31P and 19F Magic Angle Spinning Nuclear Magnetic Resonance (MAS-NMR). The 29Si spectra indicate a predominantly Q33Al and Q44Al structure where the Q33Al species represents a silicon with one non-bridging oxygen and three Si-O-Al linkages and the Q44Al species a silicon with four Si-O-Al bonds. Aluminium was found in predominantly four coordinate sites, but glasses with high fluorine contents showed an increasing proportion of five and six coordinate aluminium. In phosphate containing glasses the phosphorus was present as Al-O-PO3(2-) type species indicating local charge compensation of Al3+ and P5+ in the glass structure. 19F MAS-NMR indicated the presence of F-Ca(n), Al-F-Ca(n), F-Sr(n), Al-F-Sr(n) and Al-F-Na(n) species where F-M(n) indicates a fluorine surrounded by n next nearest neighbour cations and Al-F-M(n) represents a fluorine bonded to aluminium with the metal, M in close proximity charge balancing the tetrahedral AlO3F species. The proportion of Al-F-M(n) species increased with increasing fluorine content of the glass and lower non-bridging oxygen contents. There was no evidence of Si-F bonds in any of the glasses. The local structure of the phosphate containing glasses with regard to fluorine, calcium, strontium and phosphate is similar to that of fluorapatite the mineral phase of tooth. This may explain the ease with which these glasses crystallize to fluorapatites and the recently observed mineralization of glass polyalkenoate cements found in vivo.