Advanced Materials in Microwaves and Optics
Anti-Fatigue Design and Manufacturing Technologies I
Behaviour of Material and Composite Structures
Silicon Science and Advanced Micro-Device Engineering II
Precision Machining VI
Materials and Applications for Sensors and Transducers
Testing and Evaluation of Inorganic Materials II
Progress in Extrusion Technology and Simulation of Light Metal Alloys
Fundamentals of Machine Design
Advances in Fracture and Damage Mechanics X
Advances in Grinding and Abrasive Technology XVI
Advanced Design and Manufacture IV
摘要: The aim of our study is the characterization and comparison of structural properties of two novel alumina/zirconia ceramics prepared by Spark Plasma Sintering and biocompatibility evaluation by using an animal model (Wistar rats). SEM, XRD and FTIR spectroscopic results are reported for structural characteristics. In vivo tests demonstrated the biocompatibility and osseointegration of the composites by complementary SEM and histological analysis of the defects in rat femur respectively the connective tissue.
摘要: The aim of this study was to investigate the response of osteoblast-like cells (MC3T3-E1) to the surface of hydroxyapatite-containing glass coating on zirconia (HA-G-Zr) in comparison to yttria stabilized zirconia (Y-TZP). The MC3T3-E1 cells were cultured on HA-G-Zr and Y-TZP specimens in 24-well tissue culture plates. Surface properties were evaluated by X-ray diffractometry, Fourier tranfer infrared microscopy (FT-IR) and scanning electron microscopy (SEM). Cell proliferation in each well was measured by MTT assay. Cell morphology was observed by SEM. Cell differentiation was evaluated by alkaline phosphatase (ALP) activity and osteocalcin levels. After the glass coating on Y-TZP, X-ray diffraction peaks due to hydroxyapatite (HA) were observed clearly. HA-G-Zr appeared on surface of uneven and roughened state, wherein microcracks on the microns in width and many voids of several microns in size were present. Time-dependent proliferation and differentiation of MC3T3-E1 cells were found in all the specimens. MC3T3-E1 cells on HA-G-Zr plates showed higher differentiation than Y-TZP. These results demonstrated that HA-G-Zr showed better cellular biocompatibility than Y-TZP.
摘要: Because of its excellent mechanical properties, yttria-stabilized zirconia is currently used as an orthopedic and dental material. In this study, we have improved the bioactivity of yttria-stabilized zirconia by a combination of electrical polarization and chemical treatment. The phase transformation from tetragonal to monoclinic ZrO2 after alkaline treatment was inhibited on positively-charged yttria-stabilized zirconia surfaces compared with negatively charged and conventional surfaces. During polarization, some oxide ions move from the positively-charged surface to the negatively charged surface, leading to an increase in oxygen vacancies on the positive surface and hence greater formation of Zr-OH when this surface was exposed to alkaline solution. This then reduced the water adsorption at this surface and consequently reduced the rate of cleavage of Zr-O-Zr bonds. The bioactivity was assessed by immersing the samples in simulated body fluid and evaluating the growth of apatite on the surfaces. The combination of polarization and alkaline treatment increased the bioactivity in vitro.
摘要: The aim of this work was the synthesis of bioactive magnetic particles (BMP) which are expected to form a thin apatite layer on its surface that may bond to bone with the osseous carcinogen tissue. Magnetite and Mg0.6Ca0.4Fe2O4 nanoparticles were obtained by a reverse co-precipitation and sol-gel methods, respectively. Magnetite particles were coated with chitosan in order to obtain a stable ferrofluid. Then both ferrites were biomimetically treated using two different simulated body fluids (SBF and 1.5 SBF). An apatite layer was formed on both types of BMP after the biomimetic treatment. Both ferrites showed superparamagnetic behavior before and after the apatite formation. Their time-dependent temperature profiles were measured under the effect of an AC magnetic field (AMF). After less than 20 min of applying the AMF an appropriate temperature for hyperthermia treatment was obtained. No citotoxicity was observed after osteosarcoma cell culture testing of BMP. Furthermore, after applying an AMF to the cells in contact with the BMP, the cells viability decreased considerably.
摘要: The current trends in bioactive ceramics point out the ionic substitution in hydroxyapatite (HA) as a concrete way to create new active ceramics with a high developed biomimetic character. Accordingly, our objective in this work was investigating the effects of the simultaneous replacement of Ca2+ ions for Mg2+, Sr2+ and Mn2+ into the crystalline structure of HA.
摘要: Phase-pure nanostructured silver-doped hydroxyapatite (nAgHA) of various Ag contents was synthesised. These nAgHA were then evaluated in-vitro using human mesenchymal stem cells (hMSCs) and Escherichia coli (E. coli). Results revealed that hMSCs grew generally well on all nAgHA at all time points. In addition, fewer E. coli were seen attaching on the surface of all nAgHA. Hence, this work demonstrated that nAgHA offers considerable potential as a biomaterial.
摘要: In this work, nanocomposites of hydroxyapatite and Pluronic F127 were prepared by a wet chemical method, using acid-basic reaction with Ca/P ratio of 1.67 in 10% (m/V) Pluronic F127 at 0, 37 and 90°C. The final concentration of Pluronic F127 was adjusted to 37% (m/V) at 4°C. Afterwards, the samples were lyophilized. Characterization was performed in purified samples (after Pluronic F127 removal), samples with 10% (m/V) of Pluronic F127 and calcined samples at 1000°C by X-ray diffraction (XRD), Raman spectroscopy and scanning electron microscopy (SEM). Analyses by XRD of non-calcined samples showed that hydroxyapatite was obtained, in which the samples prepared at 0°C exhibited larger peaks attributed to lower crystallite sizes. For the calcined samples, both Raman spectroscopy and XRD exhibited hydroxyapatite for the syntheses at 37 and 90°C whereas the one prepared 90°C were identified as β-tricalcium phosphate (β-TCP). Morphological analysis by SEM indicated that the hydroxyapatite was sphere or rod agglomerates in mesoporous morphology for the nanocomposites prepared at 0 and 37°C, while the sample prepared at 90°C was nanospheres agglomerated into a smother matrix. After Pluronic F127 removal, samples fabricated at 0 and 37 °C exhibited coalescence of the nanostructures, whereas the sample synthesized at 90°C kept mesoporous. Calcined samples showed sintering and some rods structures.
摘要: The pursuit for an ideal bone substitute remains the main focus of many tissue engineering researchers. Among the myriad types of grafts available, synthetic bone grafts are of special importance, because it is available in large amounts, reduce the surgical trauma and eliminate the risk of diseases’ transmission. In this context, bioactive glasses have received attention mostly due to its described biocompatibility and rapid rate of surface reactivity when compared with other materials, allowing for faster interactions with the local tissue. The addition of niobium to this material has been shown as increasing the chemical resistance of the compound and providing greater stability. However, alterations on the chemical composition of biomaterials may impact on its biocompatibility. Therefore, the aim of this study was to evaluate the in vitro biocompatibility of bioglass-Niobium (BgNb) granules, in comparison with standard commercial bioglass (Biogran®) throughout an interesting multiparametrical approach, employing Phenol 2% and dense polystyrene beads as positive and negative controls, respectively. Extracts from each material were prepared by 24 hours incubation in culture medium (DMEM). Human primary osteoblasts were then exposed for 24 hours to each extract and cell viability was evaluated by three parameters: mitochondrial activity (XTT method), membrane integrity (neutral red dye uptake) and cell density (crystal violet dye exclusion test). BgNb extracts were highly compatible, since the levels of viable cells were similar to the control group (unexposed cells), on all parameters studied. The mean cell density on the Biogran® group was slightly lower than BgNb, even though this material was also non-cytotoxic. The excellent in vitro response for BgNb granules indicates the suitability of this material to future studies on its biological and physical properties when applied in vivo.
摘要: In most biphasic composite systems consisting of sol-gel derived bioactive glass and a second system that is usually used as a reinforcing agent, thorough stirring is necessary to prevent the precipitation of the grains of the second system. Consequently, the aim of this work is to investigate the impact of various stirring rates on the crystallinity and bioactivity of a bioactive glass in the system 58S. Sol-gel-derived bioactive glass (58S) was produced as described in literature. During the gelation, stirring rates of 0, 200, 400, 600 and 800 rpms were applied producing, respectively, the corresponding glass powders. The in vitro bioactivity of the powders was tested in Simulated Body Fluid (SBF) for various immersion times, while the solution was renewed after 6h, 24h and then every 2 days. Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and X-ray Diffractometry (XRD) were used to characterize all materials before and after immersion in SBF solution. FTIR and XRD measurements of all powders revealed mainly the formation of an amorphous glass, while the main crystalline phase was identified to be Ca2SiO4. After immersion in SBF solution for 12h, SEM microphotographs revealed apatite formation on the surface of all samples, while FTIR and XRD confirmed the aforementioned findings. Furthermore, since EDS analysis proved a mean molar Ca/P ratio of about1.7 after 6 days of immersion of all samples- besides those stirred at 400 and 600rpm- it can be assumed that a thick apatite layer was formed covering the whole surface.