材料表面化学和流体剪切力共同刺激对人脐静脉内皮细胞的影响

背景:组织工程骨内缺乏完善的脉管系统,其中血管化是限制其广泛应用的关键,适当的基质化学和流体剪切力刺激能促进血管内皮细胞增殖分化和发挥功能,指导支架材料的设计制作。目的:探究不同化学官能团和流体剪切力对人脐静脉内皮细胞的影响,以期找到材料化学与流体剪切力对人脐静脉内皮细胞调控的高效组合。方法:在玻片表面分别制备以OH、CH3和NH2为末端化学官能团的自组装单分子膜,以空白玻片作为对照;将人脐静脉内皮细胞分别接种于4组玻片表面,培养15 min内检测ATP的释放量,培养1 h内检测NO的释放量,培养1 h后Western blotting检测内皮型一氧化氮合酶的表达,培养48 h后激光共聚焦显微镜观察黏着斑及F肌动蛋白的形成。将人脐静脉内皮细胞分别接种于4组玻片表面,当细胞融合至80%时给予加载1.5 N/m2流体剪切力1 h(分别为OH-FSS组、CH3-FSS组、NH2-FSS组和FSS组),加载15 min内检测ATP的释放量,加载1 h内检测NO的释放量,加载1 h后Western blotting检测内皮型一氧化氮合酶的表达。结果与结论:(1)单纯化学刺激对人脐静脉内皮细胞的ATP、NO释放与一氧化氮合酶表达无明显影响,加载FSS刺激可增加ATP、NO的释放与内皮型一氧化氮合酶表达;当材料化学和流体剪切力同时作用时,人脐静脉内皮细胞释放的ATP和NO量及内皮型一氧化氮合酶表达与材料化学密切相关,其中NH2-FSS组中的ATP和NO释放量及内皮型一氧化氮合酶表达最高,其次为FSS组,CH3-FSS组和OH-FSS组最低;(2)激光共聚焦显微镜下可见,NH2组有大量黏着斑和细胞骨架蛋白F肌动蛋白,其次为对照组,CH3组和OH组最少;(3)结果表明,NH2官能团和流体剪切力共同作用时人脐静脉内皮细胞对剪切力刺激产生高效应答,其机制可能是在NH2表面上形成了最佳的黏着斑和F肌动蛋白。

Research progress on carbon-based zinc-ion capacitors

Zinc-ion capacitors(ZICs),which consist of a capacitor-type electrode and a battery-type electrode,not only possess the high power density of supercapacitors and the high energy density of batteries,but also have other advantages such as abundant resources,high safety and environmental friendliness.However,they still face problems such as insufficient specific capacitance,a short cycling life,and narrow operating voltage and temperature ranges,which are hindering their practical use.We provide a comprehensive overview of the fundamental theory of carbon-based ZICs and summarize recent research progress from three perspectives:the carbon cathode,electrolyte and zinc anode.The influence of the structure and surface chemical properties of the carbon materials on the capacitive performance of ZICs is considered together with theoretical guidance for advancing their development and practical use.

Low temperature solid-phase sintering of sintered metal fibrous media with high specific surface area

A procedure of low temperature solid-phase sintering（LTSS） was carried out to fabricate sintered metal fibrous media（SMFM） with high specific surface area.Stainless steel fibers which were produced by cutting process were first plated with a coarse copper coating layer by electroless plating process.A low-temperature sintering process was then completed at about 800 °C for 1 h under the protection of hydrogen atmosphere.The results show that a novel SMFM with complex surface morphology and high specific surface area（0.2 m2/g） can be obtained in this way.The effect of sintering temperature on the surface morphology and specific surface area of SMFM was studied by means of scanning electron microscopy and Brunauer-Emmett-Teller.The damage of micro-structure during the sintering process mainly contributed to the loss of specific surface area of SMFM and the optimal sintering temperature was 800 °C.

Preparation and characterization of different surface modified SiCp reinforced Al-matrix composites

The effects of SiCp surface modifications(Cu coating,Ni coating and Ni/Cu coating)on the microstructures and mechanical properties of Al matrix composites were investigated.Surface modification of SiC particles with Cu,Ni and Cu/Ni,respectively,was carried out by electroless plating method.SiCp/Al composites were prepared by hot pressed sintering followed by hot extrusion.The results show that the surface modification of SiC particles plays an effective role,which is relative to the type of surface coating,and the interfacial bonding become stronger in the following order:untreated SiCp<Ni(Cu)-coated SiCp<Ni/Cu-coated SiCp.The Ni/Cu-coated SiCp/Al composites exhibit the best comprehensive mechanical properties,with ultimate tensile strength(σUTS)and fracture strain(εf)of 389 MPa and 6.3%,respectively.Compared with that of untreated-SiCp/Al composites,theσUTS andεf are enhanced by 19.3%and 57.5%.

Li_(1.4)Al_(0.4)Ti_(1.6)(PO_(4))_(3) coated Li_(1.2)Ni_(0.13)Co_(0.13)Mn_(0.54)O_(2) for enhancing electrochemical performance of lithium-ion batteries

Lithium(Li)-rich manganese(Mn)-based cathode Li_(1.2)Ni_(0.13)Co_(0.13)Mn_(0.54)O_(2)(LRNCM)has attracted considerable attention owing to its high specific discharge capacity and low cost.However,unsatisfactory cycle performance and poor rate property hinder its large-scale application.The fast ionic conductor has been widely used as the cathode coating material because of its superior stability and excellent lithium-ion conductivity rate.In this study,Li_(1.2)Ni_(0.13)Co_(0.13)Mn_(0.54)O_(2) is modified by using Li_(1.4)Al_(0.4)Ti_(1.6)(PO_(4))_(3)(LATP)ionic conductor.The electrochemical test results show that the discharge capacity of the resulting LRNCM@LATP1 sample is 198 mA·h/g after 100 cycles at 0.2C,with a capacity retention of 81%.Compared with the uncoated pristine LRNCM(188.4 m A·h/g and 76%),LRNCM after the LATP modification shows superior cycle performance.Moreover,the lithium-ion diffusion coefficient D_(Li+)is a crucial factor affecting the rate performance,and the D_(Li+)of the LRNCM material is improved from 4.94×10^(-13) to 5.68×10^(-12)cm^(2)/s after modification.The specific capacity of LRNCM@LATP1 reaches 102.5 mA·h/g at 5C,with an improved rate performance.Thus,the modification layer can considerably enhance the electrochemical performance of LRNCM.

Two-dimensional titanium carbide MXenes as efficient non-noble metal electrocatalysts for oxygen reduction reaction

MXenes, a new family of multifunctional two dimensional(2D) solid crystals integrating high electroconductivity and rich surface chemistries, are promising candidates for electrolysis, which, however, have rarely been reported. Herein, free-standing ultrathin 2D MXene nanosheets were successfully fabricated from bulky and rigid MAX phase ceramics by liquid exfoliation with HF etching(delamination) and TPAOH intercalation(disintegration).The high oxygen reduction reaction(ORR) performance has been obtained, due to the extremely small thickness of the asfabricated Ti3C2 around 0.5–2.0 nm, equivalent to the dimensions of single-layer or double-layer Ti3C2 nanosheets in thickness. The ORR performance of the obtained Ti3C2 MXene-based catalyst exhibits desirable activity and stability in alkaline media. This study demonstrates the potential of earth-abundant 2D MXenes for constructing high-performance and cost-effective electrocatalysts.

Synthesis of TiO_2 photocatalysts with abundant surface defects using a TiO_2@NaCl precursor

TiO2 nanoparticles have been synthesized by using a TiO2@NaCl core-shell structure as the precursor. The surface defects were well preserved by the NaCl shell, and therefore high oxygen adsorption capacity was observed. After the NaC1 shell was removed, the resulting pure TiO2 nanoparticles were of anatase phase and uniform size of around 20-24 nm. The presence of an abundance of surface defects contributes to the high photocatalytic activity of the synthesized materials, and the TiO： mate- rials obtained from the TiO2@NaCl precursor can be used as efficient photocatalysts for degradation of rhodamine B under UV light irradiation.

The active-to-passive oxidation transition mechanism and engineering prediction method of C/SiC composites

This paper studied the active-to-passive oxidative mechanism of C/SiC composite under high temperature and oxidative conditions. An analytic model and computational method were established based on the process of gas diffusion in boundary layer and the equilibrium relations in surface chemical reactions. Simultaneously, an engineering equation to predict the oxygen partial pressure of active-to-passive transition was derived under the specific temperature zone. The results indicated that the active-to-passive oxidation transition of C/SiC is closely related to the composition of the material. At certain temperature and oxygen partial pressure conditions, the composite with high carbon content is prone to cause active oxidation which is negative to the oxidation resistance of the material.

Effect of surface area and heteroatom of porous carbon materials on electrochemical capacitance in aqueous and organic electrolytes

A series of porous carbon materials with wide range of specific surface areas and different heteroatom contents had been prepared using polyaniline as carbon precursor and KOH as an activating agent. Effect of surface area and heteroatom of porous carbon materials on specific capacitance was investigated thoroughly in two typical aqueous KOH and organic 1-butyl-3- methylimidazolium tetrafluoroborate/acetonitirle electrolytes. The different trends of capacitance performance were observed in these two electrolytes. Electrochemical analyses suggested that the presence of faradaic interactions on heteroatom-enriched carbon materials in organic environment is less significant than that observed in aqueous electrolytes. Thus, in aqueous electrolyte, a balance between surface area and heteroatom content of activated porous carbon would be found to develop a supercapacitor with high energy density. In organic electrolyte, the capacitance performance of porous carbon is strongly dependent on the surface area. The results may be useful for the design of porous carbon-based supercapacitor with the desired capacitive performance in aqueous and organic electrolytes.

Activated pyrolysed bacterial cellulose as electrodes for supercapacitors

In this paper, the bacterial celluloses(BCs) were pyrolysed in nitrogen and then activated by KOH to form a porous three- dimension-network electrode material for supercapacitor applications. Activated pyrolysed bacterial cellulose(APBC) samples with enlarged specific surface area and enhanced specific capacitances were obtained. In order to optimize electrochemical properties, APBC samples with different alkali-to-carbon ratios of 1, 2 and 3 were tested in two electrodes symmetrical capacitors. The optimized APBC sample holds the highest specific capacitance of 241.8 F/g, and the energy density of which is 5 times higher than that of PBC even at a current density of 5 A/g. This work presents a successful practice of preparing electrode material from environment-friendly biomass, bacterial cellulose.

Toxic effects of metal oxide nanoparticles and their underlying mechanisms

Nanomaterials have attracted considerable interest owing to their unique physicochemical properties.The wide application of nanomaterials has raised many concerns about their potential risks to human health and the environment.Metal oxide nanopartides（MONPs）,one of the main members of nanomaterials,have been applied in various fields,such as food,medicine,cosmetics,and sensors.This review highlights the bio-toxic effects of widely applied MONPs and their underlying mechanisms.Two main underlying toxicity mechanisms,reactive oxygen species（ROS）-and non-ROS-mediated toxidties,of MONPs have been widely accepted.ROS activates oxidative stress,which leads to lipid peroxidation and cell membrane damage.In addition,ROS can trigger the apoptotic pathway by activating caspase-9 and-3.Non-ROS-mediated toxicity mechanism includes the effect of released ions,excessive accumulation of NPs on the cell surface,and combination of NPs with specific death receptors.Furthermore,the combined toxicity evaluation of some MONPs is also discussed.Toxicity may dramatically change when nanomaterials are used in a combined system because the characteristics of NPs that play a key role in their toxicity such as size,surface properties,and chemical nature in the complex system are different from the pristine NPs.

Comparison of cellular responses across multiple passage numbers in Ba/F3-BCR-ABL cells induced by silver nanoparticles

With the rapid development of nanotechnology and increasingly broad bio-application of engineered nanomaterials, their bio- hazards have become a serious public concern. It is believed that the chemical nature, particle size, morphology, and surface chemistry of nanomaterials are key parameters that influence their toxicity. Although cultured ceils have been widely used to evaluate nanomaterial toxicity, it remains unclear whether the passage of these cells affects the evaluation results. In the pre- sent study, Ba/F3 cells transfected with the BCR-ABL gene were subcultured to study the effect of passage number on cell sta- bility and their cellular responses upon exposure to nanomaterials. The results demonstrated that proliferation, cellular senes- cence, BCR-ABL gene expression, cell cycle and apoptosis were stable across multiple passages. Senescence and BCR-ABL gene expression of cells from different passage cells were unchanged when treated with silver nanoparticles （AgNPs）. In addi- tion, the cells at multiple passage numbers were all arrested in the G2/M phase and apoptosis was induced by the AgNPs. These nanoparticles could enter cells via endocytosis and localize in the cndosomes, which were also not influenced by passage number. These data suggest that short-term passage would not affect cultured cell stability and toxicity assessment using these cells would be consistent when maintained appropriately.

Non-spherical abrasives with ordered mesoporous structures for chemical mechanical polishing

The chemical mechanical polishing(CMP)technology has been widely used for surface modification of critical materials and components with high quality and efficiency.In a typical CMP process,the mechanical properties of abrasives play a vital role in obtaining the ultra-precision and damage-free surface of wafers for improvement of their performances.In this work,a series of fine structured rod-shaped silica(RmSiO2)-based abrasives with controllable sizes and diverse ordered mesoporous structures were synthesized via a soft template approach,and successfully applied in the sustainable polishing slurry for improving the surface quality of cadmium zinc telluride(CZT)wafers.Compared with commercial silica gel,solid and mesoporous silica spheres,the RmSiO2 abrasives present superior elastic deformation capacity and surface precision machinability on account of their mesoporous structures and rod shapes.Especially,ultra-precision surface roughness and relatively effective material removal speed were achieved by the CMP process using the RmSiO2 abrasives with a length/diameter(L/d)ratio of 1.In addition,a potential CMP mechanism of the developed polishing slurry to CZT wafer was elucidated by analyzing X-ray photoelectron spectra and other characterizations.The proposed interfacial chemical and mechanical effects will provide a new strategy for improving abrasives’machinability and precision manufacture of hard-to-machine materials.