Papers by Author: Aldo Roberto Boccaccini

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Authors: Xanthippi Chatzistavrou, Konstantinos M. Paraskevopoulos, Vehid Salih, Aldo Roberto Boccaccini, Toshihiro Kasuga
Abstract: The aim of this work was to improve a newly developed family of glass-ceramic composite materials by incorporating silver ions in the ceramic structure, thus developing new Ag-doped materials with the ability of showing antibacterial activity for dental applications. Two different sol-gel methodologies were applied for the fabrication of colorless, homogenous and chemically durable materials which can slowly release silver ion for relatively long periods. Both methods led to the successful development of Ag-doped glass-ceramics with silver ions incorporated in the structure that can slowly release in buffer solution, during a period of 45 days. The potential, application of these materials involve the development of bioactive surfaces on dental substrates which can seal the marginal gap creating a bacterial free environment finally supporting the success of dental restorations.
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Authors: Qiang Chen, Sandra Cabanas-Polo, Ya Ping Ding, Aldo Roberto Boccaccini
Abstract: 45S5 bioactive glass (BG) based multilayer coatings on stainless steel were produced by a combination of electrophoretic deposition (EPD) and layer-by-layer (LbL) deposition. The properties of the multilayer coating were tested with different characterization methods including SEM, FTIR, XRD, laser profilometer and water contact angle measurements. Degradation and in-vitro bioactivity behaviors were tested in simulated body fluid (SBF) over different time periods. The decomposition of the coating was inhibited and the hydroxyapatite (HA) formation after short immersion period (0.5d) was confirmed. At the same time, levofloxacin, used as a model antibiotic, was incorporated into the multilayer structure for antibacterial purpose.
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Authors: Aldo Roberto Boccaccini, J.J. Blaker, V. Maquet, R. Jerome, S. Blacher, Judith A. Roether
Abstract: Porous bioresorbable and bioactive composite materials designed for applications as scaffolds in tissue engineering are discussed. The systems fabricated by thermally induced phase separation method and based on poly(D,L-lactide) (PDLLA) or poly(lactic acid-co-glycolic acid) (PLGA) with additions of bioactive glass particles (45S5 Bioglass®) are described in detail. The scaffolds exhibit a well-defined, oriented and interconnected porosity. The porosity structure of foams with and without Bioglass® was characterised by scanning electron microscopy. The in vitro bioactivity and degradability of the composite foams were investigated in contact with phosphate buffer saline (PBS) and simulated body fluid (SBF). High chemical reactivity of scaffolds in SBF, which leads to the prompt formation of bonelike hydroxyapatite crystals on the material surfaces, indicates an enhanced bioactive character of the composites and therefore their potential for use as bone tissue engineering scaffolds.
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Authors: Aldo Roberto Boccaccini, E.J. Minay, D. Krause
Abstract: 45S5 Bioglass® coatings have been produced on superelastic nickel-titanium wires using electrophoretic deposition (EPD). Aqueous suspensions of Bioglass® particles (< 5 &m mean particle size) were used. EPD led to the formation of thick and uniform coatings covering the wires very homogeneously, without the development of any microcracks during the drying stage. Best results were achieved with suspensions containing 20 wt% Bioglass®, an applied voltage of 5 V, and a deposition time of 5 min. Samples sintered for 1 hour at temperatures > 800 °C exhibited diffusion of nickel and titanium into the Bioglass® coating. Scanning electron microscopy (SEM) was used to analyse the microstructure of the Bioglass® coatings in terms of level of uniformity, densification, and to discover the possible presence of microcracks, as well as to gain information about the thickness of the coating produced on the different substrates. The results demonstrate that the EPD technique is a very convenient method to produce uniform Bioglass® coatings on wires for biomedical applications.
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Authors: Aldo Roberto Boccaccini, Lutz Christian Gerhardt
Abstract: Carbon nanotubes (CNTs) are composed of two-dimensional hexagonal graphite sheets rolled up to form into a seamless hollow tube or cylinder of diameters ranging from 0.7 to 100 nm and length of several micrometres up to several millimetres [1, 2]. CNTs can be synthesised in two configurations, as single-walled nanotubes (SWCNTs) and multi-walled nanotubes (MWCNTs). Whereas SWCNTs are made of one tubular structure, MWCNTs consist of concentrically arranged carbon tubes with a typical spacing of ≈ 0.34 nm between the different layers. Owing to their remarkable structural characteristics (light weight, high aspect ratio, high specific surface area), as well as attractive mechanical (high stiffness and strength), electrical (high conductivity) and chemical (versatile surface chemistry, easily to functionalise) properties [2], there is increasing interest in biomedical applications of CNTs.
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Authors: Cengiz Kaya, Figen Kaya, Johann Cho, Judith A. Roether, Aldo Roberto Boccaccini
Abstract: Electrophoretic deposition (EPD) has been demonstrated to be a convenient processing technique to fabricate composite ceramic coatings containing ordered arrays of carbon nanotubes. In this investigation, EPD was used to coat Ti6Al4V medical implants with hydroxyapatite (HA) layers reinforced with surface functionalized multi-walled carbon nanotubes (MWCNTs). The functionalization of MWCNTs by treating them with an acid mixture was successfully achieved in order to create functional groups on the MWCNT surfaces enabling them to be homogeneously dispersed in water. The surface treatment was also used to induce the adsorption of HA nanoparticles on MWCNT surfaces. Some critical issues, such as microcracking and peeling of HA layers after EPD, were effectively solved by the use of MWCNTs.
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Authors: Johann Cho, Aldo Roberto Boccaccini
Abstract: Carbon nanotubes (CNTs) are promising reinforcing elements for structural composites due to their remarkable mechanical properties. The impressive electrical and thermal properties of this new form of carbon also make CNTs containing composites ideal candidates for multifunctional applications. In the past decade, researchers have investigated CNTs as toughening inclusions to overcome the intrinsic brittleness of ceramics and glasses. Although there are numerous investigations available in the literature, a significant progress has not occurred or it has been rather slow compared to advances in the field of CNT/polymer matrix composites. This paper reviews current trends in research and development efforts on the use of CNTs for fabrication of ceramic and glass matrix composite materials. The review includes a summary of key issues related to the optimisation of CNT-based composites and an overview of investigations dealing with processing techniques developed to optimise dispersion quality, interfaces and density. The mechanical properties of as-produced composites are discussed and a comprehensive comparison of data available for different matrix materials is presented. Finally, the potential applications of the resulting CNT/inorganic matrix composites and the scope for future developments in the field are highlighted.
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Authors: Lukáš Řehořek, Zdeněk Chlup, Ivo Dlouhý, Aldo Roberto Boccaccini
Abstract: Fracture behaviour and mechanical properties are the key features when a material for given application is supposed to be selected. Advanced glass ceramics composites are perspective structural materials for many applications due to their low production expenses and satisfactory properties even at elevated temperatures. Borosilicate glass matrix composite reinforced by alumina platelets was investigated to describe toughening mechanisms and their changes in a wide range of temperatures (from room temperature up to glassy transition temperature Tg). The dissipation of energy by bridging and/or deflection of propagating crack by alumina platelets uniformly dispersed in the glass matrix were the main toughening mechanisms observed. The alumina platelets have a higher ability to deflect propagating crack in comparison with spherical or rectangular particles having the same volume. Three and four point bend test for Young’s modulus and flexural strength determination was used. Fracture toughness determination was conducted using chevron notch technique. More than 100% increase of fracture toughness was observed when 30% of alumina platelets were added in to borosilicate matrix.
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Authors: Kean Khoon Chew, Sharif Zein Sharif Hussein, Ahmad Abdul Latif, David S. McPhail, Aldo Roberto Boccaccini
Abstract: Stainless steel (SS) is often used for orthopaedic and dental implants because of its excellent mechanical characteristics. However, from an electrochemical perspective, SS can be susceptible to corrosion-related problems. Inorganic bioactive coatings on SS surfaces are reported to impart corrosion resistance and enhance biocompatibility. In this paper, hydroxyapatite (HA) coatings were developed on SS 316L by an electrophoretic deposition (EPD) technique at applied deposition voltages from 10 to 60 V in an acidic aqueous solution. The present study was performed to optimise the applied voltage required to produce stable HA coatings on SS 316L. Their corrosion resistance in simulated body conditions were investigated using the potentiodynamic polarisation curves. The results of the electrochemical studies revealed that the optimal applied voltage for EPD of HA on SS 316L was 40 V. The polarisation parameters, such as the corrosion potential, breakdown potential and repassivation potential of HA coated materials demonstrated nobler behaviours than the uncoated SS 316L. These results validated the successful formation of stable and protective HA coatings on SS 316L.
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Authors: Xanthippi Chatzistavrou, Nikolaos Kantiranis, Lambrini Papadopoulou, Eleana Kontonasaki, Aldo Roberto Boccaccini, Petros Koidis, Konstantinos M. Paraskevopoulos
Abstract: In this study new ternary bioactive mixtures were investigated, which are appropriate for applications as coatings on the surface of dental ceramics. The fabrication of mixtures based on the combination of dental ceramic, hydroxyapatite and bioactive glass was demonstrated. The mixtures were characterized by FTIR, XRD and SEM and their bioactive behavior was investigated by immersion in Simulated Body Fluid (SBF). The ternary mixture consisted of a high fusing leucite-feldspathic dental ceramic which exhibited the highest bioactive behavior assigned to the characteristic crystal phases occurring under the specific heat treatment investigated.
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