负偏压对多弧离子镀 TiN 涂层大颗粒形貌及像素分布的影响

目的分析不同负偏压下Ti N涂层表面的大颗粒数量、尺寸和面积以及像素分布,为多弧离子镀技术的工业化应用提供基础数据。方法采用多弧离子镀膜技术,以脉冲负偏压为变量,在硬质合金表面沉积Ti N涂层。用扫描电子显微镜对涂层表面形貌进行表征,并利用Image J软件对表面大颗粒的数量和尺寸进行分析,对像素分布进行统计。结果随着负偏压的增加,涂层表面大颗粒的数量先增多,后减少。负偏压为100 V时,大颗粒数量最多,为1364;负偏压为300 V时,大颗粒数量最少,为750。此外随着负偏压的增加,大颗粒所占涂层面积比逐渐减小。未加负偏压时,涂层表面大颗粒所占面积比最大,为6.9%,且此时涂层的力学性能最差;采用400 V负偏压时,涂层表面大颗粒所占面积比最小,为3.3%,且此时涂层的力学性能最好。负偏压为300 V时,亮、暗像素点的个数最多,为8302;负偏压为400 V时,亮、暗像素点的个数最少,为4067。结论当占空比为30%,沉积时间为1 h,负偏压为400 V时,获得的涂层力学性能最好,颗粒数量少且尺寸小。     

Investigation of F?rster Resonance Energy Transfer (FRET) and Competition of Fluorescent Dyes on DNA Microparticles

Fluorescent labeling is widely used to investigate the structural stability and changes to DNA nano- and microstructures. Despite this, the conventional method for observing DNA structures has several limitations in terms of cost-efficiency. This paper introduces a DNA spherical particle stained with DNA intercalating dyes (SYBR Green and SYTOX Orange) as tracers and reports the interaction between multiple dyes. The interference between the dyes was analyzed in terms of Förster resonance energy transfer (FRET) and competition. The changes in the fluorescence intensity by FRET were uniform, regardless of the sequence. The competition effect could occur when several dyes were added simultaneously. These properties are expected to help in the design of multicolor tracers in bioimaging and environmental applications.     

Structure and Technofunctional Properties of Protein-Polysaccharide Complexes: A Review

Food proteins and polysaccharides are the two key structural entities in food materials. Generally, interactions between proteins and polysaccharides in aqueous media can lead to one- or two-phase systems, the latter being generally observed. In some cases of protein-polysaccharide net attraction, mainly mediated through electrostatic interactions, complex coac-ervation or associative phase separation occurs, giving rise to the formation of protein-polysac-charide complexes. Physicochemical factors such as pH, ionic strength, ratio of protein to polysaccharide, polysaccharide and protein charge, and molecular weight affect the formation and stability of such complexes. Additionally, the temperature and mechanical factors (pressure, shearing rate, and time) have an influence on phase separation and time stability of the system. The protein-polysacchaide complexes exhibit better functional properties than that of the proteins and polysaccharides alone. This improvement could be attributed to the simultaneous presence of the two biopolymers, as well as the structure of the complexes. Consequently, the interesting hydration (solubility, viscosity), structuration (aggregation, gelation) and surface (foaming, emulsifying) properties of these complexes can be used in a number of domains. Among others, these could be macromolecular purification, microencapsulation, food formulation (fat replacers, texturing agents), and synthesis of biomaterials (edible films, artificial grafts).     

Polymeric Multilayers that Contain Silver Nanoparticles can be Stamped onto Biological Tissues to Provide Antibacterial Activity

The design of polyelectrolyte multilayers (PEMs) that can be prefabricated on an elastomeric stamp and mechanically transferred onto biomedically‐relevant soft materials, including medical‐grade silicone elastomers (E’～450–1500 kPa; E’‐elastic modulus) and the dermis of cadaver skin (E’～200–600 kPa), is reported. Whereas initial attempts to stamp PEMs formed from poly(allylamine hydrochloride) and poly(acrylic acid) resulted in minimal transfer onto soft materials, we report that integration of micrometer‐sized beads into the PEMs (thicknesses of 6–160 nm) led to their quantitative transfer within 30 seconds of contact at a pressure of ～196 kPa. To demonstrate the utility of this approach, PEMs were impregnated with a range of loadings of silver‐nanoparticles and stamped onto the dermis of human cadaver skin (a wound‐simulant) that was subsequently incubated with bacterial cultures. Skin dermis stamped with PEMs that released 0.25 ± 0.01 μg cm^?2 of silver ions caused a 6 log₁₀ reduction in colony forming units of Staphylococcus epidermidis and Pseudomonas aeruginosa within 12 h. Significantly, this level of silver release is below that which is cytotoxic to NIH 3T3 mouse fibroblast cells. Overall, this study describes a general and facile approach for the functionalization of biomaterial surfaces without subjecting them to potentially deleterious processing conditions.     

Preparation and characterization of poly(lactic‐co‐glycolic acid) microparticles containing DNA molecules encoding a malaria vaccine candidate

BACKGROUND: A novel ultrasonic atomization approach for the formulation of biodegradable poly(lactic‐co‐glycolic acid) (PLGA) microparticles of a malaria DNA vaccine is presented. A 40 kHz ultrasonic atomization device was used to create the microparticles from a feedstock containing 5 volumes of 0.5% w/v PLGA in acetone and 1 volume of condensed DNA which was fed at a flow rate of 18 ml h^?1. The plasmid DNA vectors encoding a malaria protein were condensed with a cationic polymer before atomization. RESULTS: High levels of gene expression in vitro were observed in COS‐7 cells transfected with condensed DNA at a nitrogen to phosphate (N/P) ratio of 10. At this N/P ratio, the condensed DNA exhibited a monodispersed nanoparticle size (Z‐average diameter of 60.8 nm) and a highly positive zeta potential of 38.8 mV. The microparticle formulations of malaria DNA vaccine were quality assessed and it was shown that the microparticles displayed high encapsulation efficiencies between 82–96% and a narrow size distribution in the range of 0.8–1.9 µm. In vitro release profile revealed that approximately 82% of the DNA was released within 30 days via a predominantly diffusion controlled mass transfer system. CONCLUSIONS: This ultrasonic atomization technique showed excellent particle size reproducibility and displayed potential as an industrially viable approach for the formulation of controlled release particles. Copyright © 2009 Society of Chemical Industry     

Functionalized Microparticles Producing Scaffolds in Combination with Cells

The development of biologically instructive biomaterials with application for tissue regeneration has become the focus of intense research over the last years. This work reports a novel approach for the production of three‐dimensional constructs for tissue engineering applications based on the assembly of chitosan microparticles exhibiting specific biological response with cells. Chitosan microparticles with a size range between 20 and 70 μm are functionalized with platelet derived growth factor (PDFG‐BB). The functionalization is achieved by previous immobilization of an anti‐PDGF‐BB antibody, using a water‐soluble carbodiimide. When incubated with a cocktail of growth factors‐platelet lysates, the previously functionalized particles are able to target PDGF‐BB from the protein mixture. In vitro studies are carried out focusing on the ability of these systems to promote the assembly into a stable 3D construct triggered by the presence of human adipose stem cells, which act as crosslinker agents and induce the formation of a hydrogel network. The presence of immobilized growth factors gives to this system a biological functionality towards control on cell function. It is also bioresponsive, as cells drive the assembly process of the microgel. These versatile biomimetic microgels may provide a powerful tool to be used as an injectable system for non‐invasive tissue engineering applications with additional control over cellular function by creating specific microenvironments for cell growth.     

RESS法制备超细萘粒子

采用常规、简便的喷射装置，建立了一套超临界溶液快速膨胀（Rapid Expansion of Supercritical Solutions,RESS)实验装置。该装置能有效地防止堵塞。以CO2为溶剂，萘为溶质，考察了喷嘴直径及收集距离对沉积微粒粒径的影响，研究了在不同的收集距离时粒径随浓液浓度的变化规律。结果表明喷嘴直径增大将使产物粒子粒径增大；在50mm的范围内，产物粒径随着收集距离的增回而明显增加，结果也显示出RESS产物是通过更小粒子之间的碰撞凝结而生长。当收集距离较大时，晶体的生长过程相比于晶核的形成过程对沉积微粒的粒径影响更大，故粒子粒径随溶液浓度增加而增大；当收集距离较小时，晶核的形成过程占主导地位，因此产物粒径随溶液浓度的增加而减小，符合经典成核理论。     

Electro-oxidation of glycerol on platinum dispersed in polyaniline matrices

Films of polyaniline (PAni) were electrosynthesized on gold and glassy carbon substrates. The morphology of the films was verified using scanning electron microscopy (SEM) and, as expected, the PAni film formed on glassy carbon presented fibrillar morphology, while that formed on gold presented fibrils on top of a more compact structure. Different amounts of platinum were electrodeposited into the polymer matrices at constant potential and the electrocatalytic activities of the electrodes were evaluated for glycerol electro-oxidation in acidic medium. Furthermore, the active areas of such modified electrodes were determined from the charges involved in the electro-oxidation of an adsorbed carbon monoxide monolayer. Considering the real active areas, the modified electrode with the gold substrate presents higher electrocatalytic activity for glycerol oxidation than that with the glassy carbon substrate. This difference is mainly related to their morphological characteristics and platinum particle sizes.     

Influence of magnetic field upon the electric capacity of a flat capacitor having magnetorheological elastomer as a dielectric

The flat capacitor is built of two non-magnetic plates (with dimensions 0.065 m × 0.050 m) between which there is a layer of magnetorheological elastomer (MRE). The thickness of the layer is 0.0015 m ± 10%. MRE is based on silicone rubber and iron particles. The iron particles diameter ranges between 0.12 μm and 0.75 μm. The electric capacity, in absence of the magnetic field, is 377 ± 1 pF. In cross magnetic field with strengths up to 94 kA/m, the flat capacitor's capacity increases by up to 200%. For well chosen values of the intensity of the magnetic field, the capacity of the flat capacitor with MRE changes with time. The experimental results obtained in this manner are discussed.     

响应面法优化松多酚微粒制备工艺

依据聚电解质自组装原理,利用黑木耳多糖酸性片段（acidic polysaccharide fragments from Auricularia auricula,AAP）和多聚赖氨酸（polylysine,PLL）将松多酚（pine polyphenols from Pinus koraiensis,PPH）包裹为微粒以防止胃环境对多酚类化合物结构的破坏,并且采用响应面试验设计优化制备工艺。通过分析AAP、PLL和PPH的质量浓度3 个因素及其交互作用对PPH微粒包埋率的影响,建立该工艺的二次多项数学模型;利用扫描电镜观察优化后PPH微粒的形貌,并在模拟胃肠道环境中检测多酚释放率。结果显示响应面回归方程拟合性良好,AAP、PLL和PPH的质量浓度对响应值均有显著影响。在AAP质量浓度为900 μg/mL、PPH质量浓度为110 μg/mL以及PLL质量浓度为30 μg/mL的条件下,PPH微粒的包埋率为（86.57±1.07）%,载药量为（24.03±0.81）%。扫描电镜观察表明PPH微粒的直径为200～500 nm,其在模拟胃环境中释放缓慢而在模拟肠道环境中释放迅速。本研究中PPH微粒包埋率的实测值与预测值相比,相对误差较低,说明本研究方法是一种适合PPH微粒制备的方法,并且优化后的PPH微粒可以降低胃环境对PPH的降解。