Biomaterial surface properties modulate in vitro rat calvaria osteoblasts response: Roughness and or chemistry?

The aim of this study was a better understanding of the regulation mechanisms of in vitro osteoblast activity on biomaterials. Rat osteoblast behaviour on different surfaces was studied. Surfaces with different roughness (and a similar surface chemistry) or with different surface chemistry (and a similar roughness) were compared. Cellular morphology was observed by scanning electron microscopy and cell adhesion was quantified using an image analysis system. Osteoblast proliferation was quantified by a MTT test and total protein content and alkaline phosphatase (ALP) activity were evaluated by spectrophotometry. Data were compared by statistical analysis.

Results showed that NiTi surface roughness did not influence osteoblasts morphology, adhesion, total protein content and ALP activity whereas it modulated cell proliferation. Roughness was shown to stimulate cell proliferation. For smooth surfaces exhibiting two different chemical compositions, adhesion rate was found to be higher on Thermanox® than on NiTi whereas proliferation was shown to be smaller. ALP activity was also modulated by surface chemistry. Thus, cell adhesion and ALP activity were found to be more governed by surface chemistry than by roughness whereas cell proliferation was shown to be modulated by roughness (this effect increasing during cell culture) and by chemistry (this effect remaining stable in time) together. Total protein content and cell morphology were found to be independent of both parameters (roughness and chemistry). Effects of surface chemistry were discussed in terms of wettability and electron acceptor/donor properties of the surfaces of interest. Immunofluorescence images of adhesion proteins could not demonstrate differences between the three surfaces.     

Strength of Anode‐Supported Solid Oxide Fuel Cells

Nickel oxide and yttria doped zirconia composite strength is crucial for anode‐supported solid oxide fuel cells, especially during transient operation, but also for the initial stacking process, where cell curvature after sintering can cause problems. This work first compares tensile and ball‐on‐ring strength measurements of as‐sintered anodes support. Secondly, the strength of anode support sintered alone is compared to the strength of a co‐sintered anode support with anode and electrolyte layers. Finally, the orientation of the specimens to the bending axis of a co‐sintered half‐cell is investigated. Even though the electrolyte is to the tensile side, it is found that the anode support fails due to the thermo‐mechanical residual stresses.     

Performance Evaluation of Solid Oxide Fuel Cells with Thin Film Electrolyte Fabricated by Binder‐Assisted Slurry Casting

A gas‐tight yttria‐stabilized zirconia (YSZ) electrolyte film was fabricated on porous NiO–YSZ anode substrates by a binder‐assisted slurry casting technique. The scanning electron microscope (SEM) results showed that the YSZ film was relatively dense with a thickness of 10 μm. La_0.8Sr_0.2MnO₃ (LSM)–YSZ was applied to cathode using a screen‐print technique and the single fuel cells were tested in a temperature range from 600 to 800 °C. An open circuit voltage (OCV) of over 1.0 V was observed. The maximum power densities at 600, 700, and 800 °C were 0.13, 0.44, and 1.1 W cm^–2, respectively.     

锌锰干电池隔膜

运用高分子电化学最新理论,系统的研究并改进了纸板电池用的浆层纸。采用特种纤维,制成带有毡状纤维层的片基、(?)布含有非水溶性万能糊料的膜层,制出具有三层结构的新型电池隔膜。与传统的浆层纸相比,在保液能力、抗胶化能力和抗结晶能力方面显示了巨大的质量优势。     

Femtosecond laser multi-patterning of zirconia for screening of cell-surface interactions

Yttria-stabilised tetragonal zirconia polycrystals (3Y-TZP) bioinert ceramics combine excellent strength and toughness, good aesthetics, high resistance to corrosion and absence of allergic reaction. However, improved osseointegration is needed as higher marginal bone loss was sometimes reported. In the present work, 3Y-TZP multi-patterned samples for rapid screening of cell-surface interactions were fabricated by femtosecond laser micromachining. Pits with well-defined edges and micrometric precision in pit diameter, depth and spacing were produced, as determined by white light interferometry. Pits showed a nanometric granular texture on the sidewalls and ripples at pit bottom, as attested by scanning electron microscopy. Focused ion beam analyses indicated limited laser-induced damage. Micropatterns impacted human mesenchymal stem cell (hMSC) size and morphology. Cell area and aspect ratio were mainly influenced by pit diameter, while solidity and circularity were affected by both pit diameter and depth. The pattern 30 μm diameter/10 μm depth induced the strongest osteoblastic hMSC commitment.     

二氧化锰电极放电数字模拟技术

本文建立了干电池中MnO_2电极放电的数学模型及其数字模拟技术,并给出描述MnO_2电极放电性能参量。它们是特征电流i,模型质子扩散系数Dm,初始质子浓度m。和膨胀因子B。本文通过理论计算值与实验值拟合情况表明结果合理,并具有进一步研究意义。同时给出在间放时质子在MnO_2电极中三维浓度分布曲线。     

一种分离培养人脐带Wharton's jelly间充质干细胞的新方法

目的探讨一种分离培养人脐带Wharton′s jelly间充质干细胞(mesenchymal stem cell,MSC)的新方法。方法取人脐带组织,除去动静脉后剪碎成2～5 mm3,将组织碎片浸入4 g/LⅠ型胶原酶和1 g/L透明质酸酶的混合液中,于37℃处理1 h,再用0.25%胰蛋白酶在相同条件下消化30 min,得到的消化液经70μm细胞滤网过滤后,制备单个细胞悬液,培养并传代。取P1、P3、P7代脐带Wharton′s jelly MSC,绘制细胞生长曲线;取P3代细胞,采用流式细胞术检测细胞表面标记分子,并分别采用成骨和成脂诱导培养基进行成骨及成脂诱导分化,茜素红染色和油红O染色观察结果。结果 P1、P3代脐带Wharton′s jelly MSC的增殖能力强,且P1代细胞的增殖能力强于P3代,P7代细胞的增殖能力较P3代细胞有所减弱。P3代脐带Wharton′s jelly MSC高表达CD90(99.8%)、CD105(100%)和CD166(100%),低表达CD45(0.3%)、CD14(0.1%)、CD34(0.2%)和CD79a(0.3%),不表达HLA-DR。P3代Wharton′s jellyMSC经成骨诱导后,茜素红染色可见红色结节;经成脂诱导后,油红O染色可见脂质沉积。结论本方法获得的Wharton′s jelly MSC活性好,增殖能力强,为后续实验研究及临床应用提供了理想的种子细胞。     

Palladium/Cobalt Coated on Multi‐Walled Carbon Nanotubes as an Electro‐catalyst for Oxygen Reduction Reaction in Passive Direct Methanol Fuel Cells

This work reports the synthesis of Pd‐based alloy electrocatalysts of Co supported on multi‐walled carbon nanotubes (MWCNTs) and their evaluation as cathode materials in a passive direct methanol fuel cell (PDMFC). The X‐ray diffraction (XRD) analysis showed well‐defined reflections corresponding to a face centered cubic phase of palladium. As compared to the Pd/MWCNT electrocatalyst, the bimetallic alloy electrocatalysts with the different Pd_xCo atomic ratios showed highly enhanced mass activity (MA) for the oxygen reduction reaction (ORR); however, the significant enhancement in the specific activity (SA) by a factor of about 1.2–5.6 for the ORR was found on the Pd_xCo alloy electrocatalysts in the presence and absence of methanol electrolyte solution. This enhancement SA in of the Pd‐based electrocatalysts was correlated to the changes in the lattice parameter and Pd_xCo surface composition. Surface area changes of Pd‐based electrocatalysts supported on MWCNT were evaluated using an accelerated durability test (ADT). The results obtained using the ADT were correlated to the performance of the Pd‐based electrocatalysts in the PDMFC. A better performance was obtained for the cell using Pd₃Co/MWCNT (2.53 mW cm^–2) compared to Pd/MWCNT (1.64 mW cm^–2) and Pt/C‐Electrochem (1.20 mW cm^–2) as cathode in the PDMFC. In the presence and absence of methanol the impedance Bode spectra showed one time constant that associated to follow a four electron pathway.     

Synthesis,Stabilization and Activation of Pt Nanoparticles for PEMFC Applications

Amongst the main challenges of catalyst materials for Proton Exchange Membrane Fuel Cells (PEMFCs) are activity and durability. Here we report on the synthesis of monodisperse nanoparticles and stabilization with traces of the surfactant, here Na‐AOT (bis‐(2‐ethylhexyl) sulfosuccinate sodium salt), used in the synthesis procedure. The surfactants prevent agglomeration and reduce Ostwald ripening. We compare the performance of Pt catalyst nanoparticles synthesized in dense microemulsions, Na‐AOT/heptane/water and Triton X‐100/toluene/water, with a commercial state‐of‐the‐art catalyst for the Oxygen Reduction Reaction (ORR). The produced catalyst nanoparticles were extracted onto a carbon support, Vulcan XC‐72R, washed and activated by heat‐treatment, which led to heavy agglomeration, or by electrochemical treatment, which led to an enhanced activity for ORR. Additionally, in comparison to the other two catalysts an increased durability of the platinum nanoparticles synthesized in the microemulsion of Na‐AOT/heptane/water was observed.     

Catalysts for Direct Methanol Fuel Cells

The activity of in house prepared carbon-supported Pt-Ru catalysts for methanol oxidation and carbon-supported RuSe for the oxygen reduction reaction in direct methanol fuel cells (DMFCs) was investigated. The composition of Pt-Ru/C was varied both in terms of weight loading (ratio of total metal content to carbon) as well as the ratio of Pt to Ru. The measurements were carried out in a half cell arrangement in sulphuric acid at various temperatures. The weight loading and ratio of Pt to Ru were varied in order to find out the optimum weight loading of precious metal and the temperature dependence of Pt to Ru ratio on methanol oxidation reaction. It has been found that there exists an optimum in the weight loading at 60 wt.% for carbon-supported Pt-Ru catalyst towards its maximum mass activity. While 1:1 Pt to Ru ratio exhibits a higher activity than 3:2 Pt:Ru above 60 °C, 3:2 ratio exhibits a higher activity at lower temperature. It has been observed that RuSe is inactive towards methanol and it is realised that RuSe is a potential candidate as methanol tolerant oxygen reduction catalyst. The activity of carbon supported RuSe for oxygen reduction reaction (ORR) was tested in sulphuric acid in the presence of methanol. Even though the mass specific activity of the RuSe catalyst is somewhat lower than that of Pt/C, the surface activity of carbon-supported RuSe is superior than that of carbon supported Pt which indicate the unfavourable size distribution of RuSe/C catalyst.