In vitro osteogenic differentiation of HOS cells on two types of collagen gels

HOS cell is a model strain of human osteoblasts derived from human osteosarcoma. We cultured the HOS cells on both the conventional collagen gel (neutral gel), and the gamma-crosslinked collagen gel without collagen fibrils (acidic gel). The shape of HOS cells on the neutral gel was similar to that on the culture dish. However, HOS cells on acidic gel had an elongated shape and attached each other to form a mesh-like pattern. The cells attached to the surface of both gels but scarcely penetrated their depths. We measured the biochemical markers for osteogenic differentiation in the HOS cells cultured on both the neutral gel and the acidic gel. The expressions of alkaline phosphatase and osteocalcin were detected in the HOS cells on both types of collagen gel. Deposition of the calcium also occurred on both gels although it was higher in the neutral gel than the acidic one. These results indicate the importance of collagen for the differentiation of HOS cells, but it is not dependent on the molecular structure (fibril formation) of collagen.     

狂犬病病毒糖蛋白真核表达载体的构建及其在COS-7细胞中的表达

目的构建狂犬病病毒糖蛋白基因的真核细胞表达载体,并在COS-7细胞中表达。方法培养狂犬病病毒,提取负链RNA,采用RT-PCR的方法扩增糖蛋白基因,并将该基因克隆到真核表达载体pcDNA3.1(A)上,通过脂质体介导的方法,转染COS-7细胞,用ELISA及间接免疫荧光法检测狂犬病病毒糖蛋白在COS-7细胞中的瞬时表达。结果成功构建了真核表达载体pcDNA3.1(A)/G,转染COS-7细胞后,在其培养上清中未检测到狂犬病病毒糖蛋白的表达。间接免疫荧光试验表明,pcDNA3.1(A)/G能有效地表达狂犬病病毒糖蛋白于转染的COS-7细胞膜上。结论真核细胞表达载体pcDNA3.1(A)/G能够在COS-7细胞中表达狂犬病病毒糖蛋白,为开发狂犬病病毒糖蛋白基因工程疫苗奠定了基础。     

Multifunctional Magnetic-fluorescent Nanocomposites for Biomedical Applications

Nanotechnology is a fast-growing area, involving the fabrication and use of nano-sized materials and devices. Various nanocomposite materials play a number of important roles in modern science and technology. Magnetic and fluorescent inorganic nanoparticles are of particular importance due to their broad range of potential applications. It is expected that the combination of magnetic and fluorescent properties in one nanocomposite would enable the engineering of unique multifunctional nanoscale devices, which could be manipulated using external magnetic fields. The aim of this review is to present an overview of bimodal “two-in-one” magnetic-fluorescent nanocomposite materials which combine both magnetic and fluorescent properties in one entity, in particular those with potential applications in biotechnology and nanomedicine. There is a great necessity for the development of these multifunctional nanocomposites, but there are some difficulties and challenges to overcome in their fabrication such as quenching of the fluorescent entity by the magnetic core. Fluorescent-magnetic nanocomposites include a variety of materials including silica-based, dye-functionalised magnetic nanoparticles and quantum dots-magnetic nanoparticle composites. The classification and main synthesis strategies, along with approaches for the fabrication of fluorescent-magnetic nanocomposites, are considered. The current and potential biomedical uses, including biological imaging, cell tracking, magnetic bioseparation, nanomedicine and bio- and chemo-sensoring, of magnetic-fluorescent nanocomposites are also discussed.     

Using Plasma Deposits to Promote Cell Population of the Porous Interior of Three‐Dimensional Poly(D,L‐Lactic Acid) Tissue‐Engineering Scaffolds

Cell adhesion and proliferation on poly(D,L ‐lactic acid) (P_DLLA) tissue‐engineering scaffolds is low. This is generally regarded to be due to the surface chemistry of the P_DLLA polymer, although topographic features often worsen the situation. This study reports for the first time successful deposition of a plasma polymer throughout the porous network of a three‐dimensional scaffold. This allylamine plasma deposit was used to improve cell adhesion on the P_DLLA surface. X‐ray photoelectron spectroscopy (XPS) analysis of sectioned scaffolds was used to demonstrate the penetration of nitrogen species to the inner surfaces and to compare the virgin P_DLLA scaffold and the plasma polymer coated P_DLLA scaffold with plasma‐grafted allylamine. The nitrogen concentration at the exterior and interior scaffold surfaces was greater for the plasma deposits than for the grafted surfaces, and the chemical state of the incorporated surface nitrogen using the two methods was found to be different. Evaluation in vitro was carried out by studying 3T3 fibroblast attachment, morphology, and metabolic activity on the scaffolds. Cell activity and attachment was found to be greater for the plasma deposits than the plasma‐grafted P_DLLA scaffolds, and both were greater than for the virgin P_DLLA scaffolds. It is concluded that plasma deposition is a viable method of increasing cell attachment throughout porous P_DLLA scaffolds without changing the bulk characteristics of the polymer.     

Different Magnitudes of Tensile Strain Induce Human Osteoblasts Differentiation Associated with the Activation of ERK1/2 Phosphorylation

Mechanical factors are related to periprosthetic osseointegration following total hip arthroplasty. However, osteoblast response to strain in implanted femurs is unclear because of the absence of accurate stress-measuring methods. In our study, finite element analysis was performed to calculate strain distribution in implanted femurs. 0.8-3.2% tensile strain was then applied to human osteoblasts. Higher magnitudes of strain enhanced the expression of osteocalcin, type I collagen, and Cbfa1/Runx2. Lower magnitudes significantly increased ALP activity. Among these, type I collagen expression increased with the activation of ERK1/2 phosphorylation in a strain-magnitude-dependent manner. Our study marks the first investigation of osteoblast response at different magnitudes of periprosthetic strain. The results indicate that the functional status of human osteoblasts is determined by strain magnitude. The strain distribution in the proximal region of implanted femur should be improved for osseointegration.     

Silicon solar cells produced by corona discharge

A technique for producing p-n junction silicon solar cells has been developed involving the use of a continuous gaseous discharge operating in the corona mode. The process is applicable to the production of p on n or n on p structures. Detailed results are presented for a BF₃ discharge, producing p on n cells, along with preliminary results using a PF₅ discharge, resulting in n on p cells. Efficiencies of over 8% were obtained on single crystal Si p on n cells, and of over 3% for a heavily-defected polycrystalline at AMl without anti-reflective coatings. Fill factors as high as 0.76 were obtained. Analysis of these cells include ion microprobe mass analysis and anodic stripping for concentration profiles, and capacitance-vol tage and current-voltage measurements for electrical characterization. This work was performed under the auspices of the U.S. Energy Research and Development Administration under contract number W-7504-ENG-48.     

非对称横电磁波传输室的工程设计

本文利用非对称横电磁波传输室(ATEM Cell)的特性分析公式,给出了一套ATEMCell的工程设计方法。该方法借助计算机,实现了对ATEM Cell的三大参数(特性阻抗、截止频率和横向场分布)的优化设计。该方法的特点是,计算准确度高,方便工程应用。文中提供的数据图表为工程人员提供了更便捷的设计途径。     

A Direct Ammonia Fuel Cell Using Barium Cerate Proton Conducting Electrolyte Doped With Gadolinium and Praseodymium

The performance characteristics of fuel cells based on proton conducting BaCeO₃ solid electrolyte doubly doped with gadolinium and praseodymium are reported. The amount of praseodymium doping is systematically varied in order to optimize the fuel cell performance. Fuel cells incorporating the optimum amount of praseodymium exhibit power density levels enhanced by a factor of three, compared to those incorporating undoped BaCeO₃. The performance of the fuel cell is essentially the same irrespective of the fuel used. However, the performance of the fuel cell is slightly better in hydrogen than in ammonia. Nevertheless, fuel cells operated in ammonia show a greater decrease in peak power density with decreasing temperature than those operated in hydrogen. This behaviour suggests that alternative anode materials need to be utilized at lower operating temperatures.