Comparison of the cytotoxic and inflammatory responses of titanium particles with different methods for endotoxin removal in RAW264.7 macrophages

It is generally accepted that periprosthetic bone resorption is initiated through aseptic inflammation aggravated by wear particles that are generated from artificial joint. However, some studies have demonstrated that “endotoxin-free” wear particles are almost completely unable to stimulate the macrophage-mediated production of proinflammatory cytokines. Here, we compare the titanium particles with different methods of endotoxin removal. The results indicated that different titanium particle preparation dosages did not significantly change particle size, morphology, and chemical composition. But it could cause variations in the endotoxin concentration of titanium particles and inflammatory responses in RAW264.7 macrophages. The particles with higher endotoxin levels correlated with more extensive inflammatory responses. When testing endotoxins using the supernatant of particle suspensions, it would lead to false negative results compared with testing the particle themselves. And when using the particles themselves, all the particles should be removed by centrifugation to avoid particle interference before the absorbance value was determined. Therefore, we suggest that research concerning wear particles should completely describe the endotoxin testing process, including endotoxin removal from particles and the details of endotoxin testing. Moreover, future research should focus on the surface of wear particles (the potential role of adherent endotoxin) rather than the particles themselves.     

Comparison of cytotoxicity of pristine and covalently functionalized multi-walled carbon nanotubes in RAW 264.7 macrophages

Carbon nanotubes may be applied in different fields including biomedicine and mechanical engineering. It is important to understand the potential hazards of carbon nanotubes. In the present study, the toxicological effects of the pristine multi-walled carbon nanotubes (p-MWCNTs) and taurine functionalized multi-walled carbon nanotubes (tau-MWCNTs) were assessed on RAW 264.7 macrophages. We tested cell viability, GSH/GSSG ratio, apoptosis, intracellular calcium concentration, ultrastructural changes of cell morphology, and the release of IL-8. We observed the loss of cell viability, decline in the cellular GSH/GSSG ratio, increase of IL-8, and the increase of intracellular calcium concentration in RAW 264.7 macrophages when exposed to p-MWCNTs at high dosage. Additionally, exposure to p-MWCNTs resulted in ultrastructural and morphological changes in RAW 264.7 macrophages. In contrast, the RAW 264.7 macrophages exposed to the tau-MWCNTs did not exhibit altered morphology. Our results conclude that the tau-MWCNTs show lower toxicity than that of p-MWCNTs.     

Regulation of RAW 264.7 macrophages behavior on anodic TiO<Subscript>2</Subscript> nanotubular arrays

Titanium (Ti) implants with TiO₂ nanotubular arrays on the surface could regulate cells adhesion, proliferation and differentiation to determine the bone integration. Additionally, the regulation of immune cells could improve osteogenesis or lead in appropriate immune reaction. Thus, we evaluate the behavior of RAW264.7 macrophages on TiO₂ nanotubular arrays with a wide range diameter (from 20 to 120 nm) fabricated by an electrochemical anodization process. In this work, the proliferation, cell viability and cytokine/chemokine secretion were evaluated by CCK-8, live/dead staining and ELISA, respectively. SEM and confocal microscopy were used to observe the adhesion morphology. Results showed that the small size nanotube surface was benefit for the macrophages adhesion and proliferation, while larger size surface could reduce the inflammatory response. These findings contribute to the design of immune-regulating Ti implants surface that supports successful implantation.     

Multi-walled carbon nanotubes induce apoptosis in RAW 264.7 cell-derived osteoclasts through mitochondria-mediated death pathway

Carbon nanotubes (CNTs) have attracted great interest with respect to biomaterials, particularly for use as an implant material in bone-tissue engineering. Accordingly, the bone-tissue compatibility of CNTs and their influence on new bone formation are important issues. In the present study, we examined the effects of multi-wall carbon nanotubes (MWCNTs) on the receptor activator of nuclear factor kappaB ligand (RANKL)-supported osteoclastogenesis using a murine monocytic cell line RAW 264.7. MWCNTs significantly suppressed the differentiation of RAW 264.7 cells into osteoclasts. Treatment with MWCNTs induced apoptosis in osteoclasts as characterized by nuclear condensation, DNA fragmentation, caspase-3 activation and poly(ADP-ribose) polymerase (PARP) cleavage, but did not decrease the cell viability of the osteoblast-like cell line MC3T3-E1. MWCNTs also induced loss of the mitochondrial membrane potential (deltapsim) by regulating expression of Bcl-2 family proteins and caused release of cytochrome c from mitochondria to cytosol. MWCNTs-induced apoptosis in osteoclasts was inhibited both by cyclosporin A, a blocker of the mitochondrial permeability transition pore, and by DEVD-CHO, a cell-permeable inhibitor of caspase-3. The present study suggests that MWCNTs suppresse osteoclastogenesis via the inhibition of osteoclast differentiation and the induction of apoptosis in osteoclasts, rendering them promising candidate for the treatment of osteoclast-related diseases.     

Fabrication and characteristics of polyfluorene based organic photodetectors using fullerene derivatives

The characteristics of organic photodetectors (OPDs) by solution process using one of the polyfluorene derivatives poly(9,9-dioctylfluorene-co-bithiophene) (F8T2) and two fullerene derivatives [6-6]phenyl-C61-butyric acid methyl ester (PCBM) or N-Ts aziridinofullerene (TsAF) are investigated. F8T2:PCBM devices showed good rectifying characteristics in a dark state and photosensitive characteristics, and fast frequency responses. Weight ratio of 1:1 device showed larger photocurrent than 1:4 device and obtained over 50 MHz of cutoff frequency under reverse bias voltage of 10 V. This result suggests that F8T2:PCBM device can be applied to a photodetector for detecting several tens of megahertz optical signals under blue light irradiation. The polarity of J–V characteristics of F8T2:fullerene derivative device is strongly affected by charge injection and extraction between fullerene derivative and electrodes.     

Charge-associated effects of fullerene derivatives on microbial structural integrity and central metabolism

The effects of four types of fullerene compounds (C60, C60-OH, C60-COOH, C60-NH2) were examined on two model microorganisms (Escherichia coli W3110 and Shewanella oneidensis MR-1). Positively charged C60-NH2 at concentrations as low as 10 mg/L inhibited growth and reduced substrate uptake for both microorganisms. Scanning electron microscopy (SEM) revealed damage to cellular structures. Neutrally charged C60 and C60-OH had mild negative effects on S. oneidensis MR-1, whereas the negatively charged C60-COOH did not affect either microorganism's growth. The effect of fullerene compounds on global metabolism was further investigated using [3-13C]L-lactate isotopic labeling, which tracks perturbations to metabolic reaction rates in bacteria by examining the change in the isotopic labeling pattern in the resulting metabolites (often amino acids).1-3 The 13C isotopomer analysis from all fullerene-exposed cultures revealed no significant differences in isotopomer distributions from unstressed cells. This result indicates that microbial central metabolism is robust to environmental stress inflicted by fullerene nanoparticles. In addition, although C60-NH2 compounds caused mechanical stress on the cell wall or membrane, both S. oneidensis MR-1 and E. coli W3110 can efficiently alleviate such stress by cell aggregation and precipitation of the toxic nanoparticles. The results presented here favor the hypothesis that fullerenes cause more membrane stress 4-6 than perturbation to energy metabolism.7.     

Comparison of inter- and intra-chromosomal aberrations in blood samples exposed to different dose rates of gamma radiation

Peripheral blood samples obtained from a normal healthy volunteer were exposed in vitro to gamma radiation with various doses at different dose rates of 1.0, 0.1 and 0.0014 Gy min(-1). The exposed samples were analysed for different chromosomal aberrations such as dicentrics (DC), centric rings (CR) and double-minutes (DM). The ratio of DC chromosomes (inter) to the total number of centric rings (CR) and double-minutes (DM) (CR + DM = intra) were analysed for all the three dose rates. The study showed that the frequency of inter-arm chromosomal aberrations was more then three times higher than that observed with intra-arm chromosomal aberrations in samples exposed at a dose rate of 1.0 and 0.1 Gy min (-1). However, the frequency of inter- and intra-arm chromosomal aberrations were almost same (ratio 1:1) in samples exposed at a dose rate of 0.0014 Gy min(-1). This paper discusses the usefulness of the ratio of inter- and intra-arm chromosome aberration in finding out whether the sample was exposed to high or low dose rate radiation.     

Direct writing of semiconducting polythiophene and fullerene derivatives composite from bulk heterojunction solar cell by inkjet printing

The direct writing approach of poly(3-hexylthiophene):[6,6]-phenyl-C61-butyric acid methyl ester (P3HT:PCBM) composite from bulk-heterojunction (BHJ) solar cell was efficiently addressed by inkjet printing technology using conventional chlorobenzene ink solution. The structure of inkjet-printed P3TH:PCBM BHJ film was fabricated by the repetitive direct writing of new line overlapped partially on former line. The best structure of P3HT:PCBM film for BHJ solar cell was observed from inkjet printing condition of around 50% of droplet overlaps with 2 wt.% BHJ ink at 25 °C of substrate temperature. The maximum power conversion efficiency reached 2.83% with an open circuit voltage of 0.62 V, a short circuit current density of 8.60 mA/cm², and a fill factor of 0.53 under air mass 1.5 G irradiation (100 mW/cm²).     

C60 fullerene derivatized nanoparticles and their application to therapeutics

Fullerenes can be formed into many new materials and devices. They have a wide range of applications in medicine, electronics, biomaterials, and energy production. An overview of the nanostructure and the physical and chemical characteristics of fullerene-drug derivatives is given. The biological behavior of fullerene derivatives shows their potential to medical application fields because C(60) is rapidly absorbed by tissues and is excreted through urinary tract and enterons, which reveals low toxicity in vitro and in vivo studies. Nanomedicine has become one of the most promising areas of nanotechnology, while many have claimed its therapeutic use against cancer, human immunodeficiency virus (HIV), and neurodegenerative disorders. Water-soluble C(60) fullerene derivatives that come from chemical modification largely enhance the biological efficacy. The blood-brain barrier (BBB) is a physical barrier composed of endothelial tight junctions that restrict the paracellular permeability. A major challenge facing neuropharmacology is to find compounds that can be delivered into the brain through the bloodstream. Fullerene C(60) was demonstratively able to cross the BBB by hybridizing a biologically active moiety dyad, which provides a promising clue as a pharmacological therapy of neural disorders.     

Mechanical characteristics of self-compacting concretes with different filler materials,exposed to elevated temperatures

In this paper, the studies concern the influence that different fillers have on the properties of SCC of different strength classes when exposed to high temperatures. A total of six different SCC and two conventional concrete mixtures were produced. The specimens produced are placed at the age of 180 days in an electrical furnace which is capable of reaching 300°C at half an hour and 600°C at 70 min. The maximum temperature is maintained for an hour. Then the specimens are let to cool down in the furnace. The hardened properties measured after fire exposures are the compressive strength, splitting tensile strength, water capillary absorption and the ultrasonic pulse velocity. Explosive spalling occurred in most cases when specimens of higher strength class are exposed to high temperatures. The spalling tendency is increased for specimens of higher strength class C30/37 irrespective of the mixture type (SCC or NC) and the type of filler used.     

Hydrogen sieving and storage in fullerene intercalated graphite

The geometrical properties of recently synthesised C60 intercalated in graphite have been confirmed by density-functional-based computer simulations. The capability of this material to store molecular hydrogen by physisorption is evaluated. While the material can sieve H2 from heavier molecular gases, our free energy calculations indicate that further tuning of the system by reducing the amount of intercalated fullerene cages is necessary to achieve H2 loadings which are interesting for technical applications.     

Lateral collapse of short‐length sandwich tubes compressed by different indenters and exposed to external constraints

In this paper, sandwich tube components which consist of thin‐walled circular tubes with aluminium foam core are proposed as energy absorption systems. The sandwich tubes were laterally crushed under quasi‐static loading conditions. The sandwich tubes were crushed under two types of indenters and exposed to three different types of external constraints. The collapsing behaviour and the energy absorption responses of these systems were investigated by nonlinear finite element analysis through ANSYS‐LS‐DYNA. Various indicators which describe the effectiveness of energy absorbing systems were used as a marker to compare the various systems. It was found that the sandwich tube systems compressed by cylindrical indenters particularly the unconstrained system and the system with inclined constraints offered a very desirable force‐deflection in which the force is almost constant in the post collapse stage. The employing of external constraints was noticed as a feasible method of increasing the SEA particularly when cylindrical indenter is used.     

Estimation of dose rates to humans exposed to elevated natural radioactivity through different pathways in the island of Ikaria, Greece

A radiological survey has been carried out in the island of Ikaria based on the natural radionuclide inventory in abiotic environment and the consequent dose rate assessment for the critical groups of population. The island of Ikaria-Aegean Sea, Greece is characterised by the presence of mineral and thermo-mineral springs, which have an apparent influence on natural background radiation of the island. The levels of natural radionuclides in spring water (either for spa treatment and household use), potable water (local domestic network), and rock and soil samples were measured in this island. The concentrations of (222)Rn and natural gamma emitters were found to be significantly elevated in spring water and some rock and soil samples. In terms of NORM and TENORM, the external and internal dose rates (mSv y(-1)) were estimated in three groups of population selected on the basis of water use as: habitants of the island, working personnel and bathers in spa installations. According to the derived results, the working personnel in the thermal spa installations are exposed to significant radiological risk due to waterborne (222)Rn with a maximum dose rate up to 35 mSv y(-1), which led to overexposure in terms of the 20 mSv y(-1) professional limits. Therefore, this group can be considered as the critical one for the radiological impact assessment in the island.     

Quantitative observations of precipitation in 2.25Cr–1Mo steel exposed to different creep conditions in a power station

Samples of 2.25Cr–1Mo steel in the form of tubes have been examined in the new condition and after extended service in a power station. The differences in microstructure in terms of precipitates have been characterized using a TEM; the various precipitates present have been identified individually by using extraction replicas and energy dispersive spectroscopy analysis. The area fraction of each type of precipitate was calculated. The results have shown that the quantity of M₇C₃ precipitated within grains as well as on grain boundaries decreased markedly with the time in service while the quantity of M₆C increased in both regions. It was observed that precipitates of Mo₂C and (CrMo)₂CN, detected after aging respectively on the samples with the shorter and the longer aging times, were present only within grains. The procedure used was not accurate for identification and quantification of small VC and (VNb)C precipitates. The results of the relative quantity of M₇C₃ and M₆C, as a function of time in service, particularly on grain boundaries, showed a well defined interdependence. These results can be used as a complementary analysis for creep damage and remaining life estimation for this class of steel operating at high temperature under steady state conditions.     

碱环境下不同应力水平GFRP筋抗拉性能试验

基于ACI 440.3R-04规定的试验方法,对60 ℃碱环境下应力水平分别为0、25%和45%的玻璃纤维塑料（GFRP）筋的抗拉性能进行了试验研究。试件数量共90根,侵蚀时间分别为3.65、18、36.5、92、183天。采用SEM对腐蚀前后GFRP筋的微观形貌进行了观测,发现碱溶液造成了GFRP筋内部结构致密性的降低,且随着应力水平的增加,其降低愈发明显。在60 ℃碱溶液中侵蚀183天后,应力水平为0和25%的GFRP筋的抗拉强度分别下降了48.81%和55.56%,而弹性模量仅分别下降了5.47%和5.73%,应力水平为45%的GFRP筋则出现了断裂现象。GFRP筋的吸湿试验表明,OH^-离子在GFRP筋中的扩散过程符合Fick定律。在分析了应力水平、侵蚀时间等参数对GFRP筋抗拉性能影响的基础上,基于Fick定律提出了碱环境下带应力GFRP筋抗拉强度的退化模型。     

Nanoscale modeling of an embedded multi-shell fullerene and its application to vibrational analysis

In this paper, nanoscale modeling of a multi-shell fullerene embedded in an elastic medium and its application to vibrational analysis is investigated. The spherical layers of the multi-shell fullerene are concentrically nested, with carbon-carbon van der Waals interactions between them. Also, the whole multi-shell fullerene is influenced by polymer-carbon van der Waals forces from the surrounding elastic medium. The elasticity generated by the carbon-carbon bonds is assumed to be distributed isotropically over the fullerene surfaces. Following derivation of explicit equations for the motion of the multi-shell fullerene, vibrational behavior of a double-shell fullerene is analyzed and resonant frequencies and the associated mode shapes are determined.     

Bonding nature and structural phase transition in fullerene based nanomaterials

Rare-earth-metal-doped fullerides with a nominal composition of R3C70 (R = Sm, Eu, Yb) adopt a pseudomonoclinic structure in which C70 dimers glued with rare-earth ions are involved. High-temperature powder X-ray diffraction experiments revealed that the dimers undergo reversible first-order structural phase transitions, associated with reduction of the unit cell volume, similar to the results observed in previous high-pressure experiments. Structural analyses showed that C70 molecules are realigned to form closely packed structures, causing a reduction of volume at high temperature. The derived charge density map indicates that the transitions can be regarded as reversible structural changes from fullerene dimers to monomers. These features are ascribed to the unique bonding nature of rare-earth C70 compounds.     

Structure of polycrystalline silicon films deposited at low temperature by plasma CVD on substrates exposed to different plasma

Polycrystalline silicon (poly-Si) films were deposited on glass substrates (corning 7059) at 300°C by a plasma enhanced chemical vapor deposition (PECVD) from a SiH₄/SiF₄ mixture. All poly-Si films were prepared under the same deposition conditions on the substrates subjected to nitrogen, hydrogen and/or CF₄ plasma with different gas pressures, just before deposition of the poly-Si films. Effects of such pretreatments for substrates on the structural properties of the resultant poly-Si films have been investigated. The Si film deposited on the substrates without any pretreatments was amorphous. However, formation of a strong 〈110〉 preferentially oriented poly-Si with improved crystallinity was obtained for the films deposited on the glass substrate after plasma pretreatments, which exhibit smoother surfaces. This result was interpreted in terms of a removal of weak Si–Si bonds during nucleation and the subsequent grain growth.     

钢纤维类型对超高性能混凝土高温爆裂性能的影响

为了探寻可以有效改善超高性能混凝土（Ultra-high-performance concrete,UHPC）抗火性能的钢纤维类型,本文试验测定了不同类型钢纤维（3种普通钢纤维和2种来自于废旧轮胎的再生钢纤维）增韧UHPC及空白组混凝土的从常温至800℃高温爆裂行为和断裂能。结果显示,未掺入任何钢纤维的空白组UHPC试件全都发生了严重高温爆裂,钢纤维可以显著减轻其高温爆裂但却不能避免爆裂的发生,而掺入端钩型普通工业钢纤维（长度为35 mm,直径为0.55 mm）的UHPC呈现出最优的抗高温爆裂性能,其次是掺入未附着橡胶颗粒（RSF）的再生钢纤维（RSFR）增韧UHPC。可见,钢纤维自身性能特征显著影响了钢纤维增韧UHPC的高温爆裂,相同掺量情况下混凝土单位体积内分布密度较大的钢纤维或者分布密度较小但可以显著增加混凝土断裂韧性（断裂能）的钢纤维比较适合应用于具有较高抗火要求的UHPC结构中。