Application of gel-casting to the fabrication of 1-3 piezoelectric ceramic-polymer composites for high-frequency ultrasound devices

A modified gel-casting technique was used to fabricate a 1-3 piezoelectric ceramic/polymer composite substrate formed by irregular-shaped pillar arrays of small dimensions and kerfs. This technique involves the polymerization of aqueous piezoelectric (PZT) suspensions with added water-soluble epoxy resin and polyamine-based hardener that lead to high strength, high density and resilient ceramic bodies. Soft micromoulding was used to shape the ceramic segments, and micropillars with lateral features down to 4 m and height-to-width aspect ratios of ∼10 were achieved. The composite exhibited a clear thickness resonance mode at approximately 70 MHz and a k eff ∼ 0.51, demonstrating that the ceramic micropillars possess good electrical properties. Furthermore, gel-casting allows the fabrication of ceramic structures with non-conventional shapes; hence, device design is not limited by the standard fabrication methods. This is of particular benefit for high-frequency transducers where the critical design dimensions are reduced. © 2012 IOP Publishing Ltd.

Extraction of genomic DNA using a new amino silica monolithic column

A new amino silica monolithic column was developed for DNA extraction in a miniaturized format. The monolithic column was prepared in situ by polymerization of tetraethoxysilane (TEOS) and N-(beta-aminoethyl)-gamma-aminopropylmethyldimethoxysilane (AEAPMDMS). DNA was loaded in 50 mM tris(hydroxylmethyl)aminomethane-EDTA buffer at pH 7.0 and eluted with 300 mM potassium phosphate solution at pH 10.0. Under optimal condition, a 6.0-cm monolithic column provided a capacity of 56 ng DNA with an extraction efficiency of 71 +/- 5.2% (X +/- RSD). When the amino silica monolithic column was applied to extract genomic DNA from the whole blood of crucian carp, an extraction efficiency of 52 +/- 5.6% (X +/- SD) was obtained by three extractions. Since the chaotropic-based sample loading and organic solvent wash steps were avoided in this procedure, the purified DNA was suitable for downstream processes such as PCR. This amino silica monolithic column was demonstrated to allow rapid and efficient DNA purification in microscale.

Population genetic structure and geographical differentiation of the Chinese catfish Hemibagrus macropterus (Siluriformes, Bagridae): Evidence for altered drainage patterns

National Natural Science Foundation of China (NSFC) [2007CB411600, 30530120]

Bioelectronics meets nanomedicine for cardiovascular implants: PEDOT-based nanocoatings for tissue regeneration.

BACKGROUND: An exciting direction in nanomedicine would be to analyze how living cells respond to conducting polymers. Their application for tissue regeneration may advance the performance of drug eluting stents by addressing the delayed stent re-endothelialization and late stent thrombosis. METHODS: The suitability of poly (3, 4-ethylenedioxythiophene) (PEDOT) thin films for stents to promote cell adhesion and proliferation is tested in correlation with doping and physicochemical properties. PEDOT doped either with poly (styrenesulfonate) (PSS) or tosylate anion (TOS) was used for films' fabrication by spin coating and vapor phase polymerization respectively. PEGylation of PEDOT: TOS for reduced immunogenicity and biofunctionalization of PEDOT: PSS with RGD peptides for induced cell proliferation was further applied. Atomic Force Microscopy and Spectroscopic Ellipsometry were implemented for nanotopographical, structural, optical and conductivity measurements in parallel with wettability and protein adsorption studies. Direct and extract testing of cell viability and proliferation of L929 fibroblasts on PEDOT samples by MTT assay in line with SEM studies follow. RESULTS: All PEDOT thin films are cytocompatible and promote human serum albumin adsorption. PEDOT:TOS films were found superior regarding cell adhesion as compared to controls. Their nanotopography and hydrophilicity are significant factors that influence cytocompatibility. PEGylation of PEDOT:TOS increases their conductivity and hydrophilicity with similar results on cell viability with bare PEDOT:TOS. The biofunctionalized PEDOT:PSS thin films show enhanced cell proliferation. CONCLUSIONS: The application of PEDOT polymers has evolved as a new perspective to advance stents. GENERAL SIGNIFICANCE: In this work, nanomedicine involving nanotools and novel nanomaterials merges with bioelectronics to stimulate tissue regeneration for cardiovascular implants. This article is part of a Special Issue entitled Organic Bioelectronics - Novel Applications in Biomedicine.

Contractile and mechanical properties of epithelia with perturbed actomyosin dynamics.

Mechanics has an important role during morphogenesis, both in the generation of forces driving cell shape changes and in determining the effective material properties of cells and tissues. Drosophila dorsal closure has emerged as a reference model system for investigating the interplay between tissue mechanics and cellular activity. During dorsal closure, the amnioserosa generates one of the major forces that drive closure through the apical contraction of its constituent cells. We combined quantitation of live data, genetic and mechanical perturbation and cell biology, to investigate how mechanical properties and contraction rate emerge from cytoskeletal activity. We found that a decrease in Myosin phosphorylation induces a fluidization of amnioserosa cells which become more compliant. Conversely, an increase in Myosin phosphorylation and an increase in actin linear polymerization induce a solidification of cells. Contrary to expectation, these two perturbations have an opposite effect on the strain rate of cells during DC. While an increase in actin polymerization increases the contraction rate of amnioserosa cells, an increase in Myosin phosphorylation gives rise to cells that contract very slowly. The quantification of how the perturbation induced by laser ablation decays throughout the tissue revealed that the tissue in these two mutant backgrounds reacts very differently. We suggest that the differences in the strain rate of cells in situations where Myosin activity or actin polymerization is increased arise from changes in how the contractile forces are transmitted and coordinated across the tissue through ECadherin-mediated adhesion. Altogether, our results show that there is an optimal level of Myosin activity to generate efficient contraction and suggest that the architecture of the actin cytoskeleton and the dynamics of adhesion complexes are important parameters for the emergence of coordinated activity throughout the tissue.

A novel method of extraction of blend component structure from SANS measurements of homopolymer bimodal blends

A new method is presented for the extraction of single-chain form factors and interchain interference functions from a range of small-angle neutron scattering (SANS) experiments on bimodal homopolymer blends. The method requires a minimum of three blends, made up of hydrogenated and deuterated components with matched degree of polymerization at two different chain lengths, but with carefully varying deuteration levels. The method is validated through an experimental study on polystyrene homopolymer bimodal blends with M A≈1/2MB. By fitting Debye functions to the structure factors, it is shown that there is good agreement between the molar mass of the components obtained from SANS and from chromatography. The extraction method also enables, for the first time, interchain scattering functions to be produced for scattering between chains of different lengths. © 2014 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effects of cell-cycle arrest agents on cleavage and development of loach (Misgurnus anguillicaudatus) embryos

The aim of this study was to determine the lowest concentration of nocodazole and colchicine to arrest blastomere division during the cleavage stage of loach embryos and to assess the reversibility and toxicity of the treatments in the treated embryos. Eight-cell loach embryos were incubated for 4, 8, 12, or 16 h in 1/10x Holtfreter supplemented with either nocodazole, an inhibitor of tubulin polymerization, or colchicine, an inhibitor of tubulin assembly. Complete arrest of cell cycle was observed, at a colchicine concentration of 0.996 mM and at a nocodazole concentration of 0.275 muM, respectively (the lowest effective concentration). No major morphological alteration in chromatin was observed. Reversibility and toxicity of both agents were dose and exposure period dependent. For both agents, prolonging cleavage arrest for more than 4 h (at the effective concentrations) is detrimental to development of embryos. Nocodazole treatment was less cytotoxic, whereas the concentrations of colchicine which induce cleavage arrest were detrimental to development beyond the blastula stage. Toxic effects beyond the blastula stage could be minimized for both agents by reducing the period of treatment and concentration.

Assembly of side-functional monomers with inorganic nanometer particles

Monomers of methacrylate with various pi -conjugated pendants were designed and prepared in our laboratory, The monomer with suitable end-group was successfully assembled with nano-scale inorganic particles to form an orderly-aligned structure that showed special optical properties, both absorption and emission band were much red-shifted compared with the monomer, A new type of organic/inorganic hybrid materials was obtained by in situ polymerization of the assembly, The hybrid materials could also show special optical properties as the assembly, This might open a new route to tune the emission color.

Synthesis and characterization of an active styrlthiophene monomer and its polyurethane with second-order optical nonlinearity

A novel monomer, (trans)-7-[4-N,N-(di-beta-hydroxyethyl) amino-benzene]-ethenyl-3,5-dinitrothiophene (HBDT), and the corresponding prepolymer, polyurethane were synthesized and characterized. The details of synthesis of the monomer and its further polymerization were presented. The prepolymer and polyurethane exhibited good thermal stability and good solubility in common organic solvents. The d(33) coefficient of the poled films was determined to be 40.3 pm/V. (C) 2000 Kluwer Academic Publishers.

On the acid-base stability of Keggin Al-13 and Al-30 polymers in polyaluminum coagulants

The acid-base stabilities of Al-13 and Al-30 in polyaluminum coagulants during aging and after dosing into water were studied systematically using batch and flow-through acid-base titration experiments. The acid decomposition rates of both Al-13 and Al-30 increase rapidly with the decrease in solution pH. The acid decompositions of Al-13 and Al-30 with respect to H+ concentration are composed of two parallel first-order and second-order reactions, and the reaction orders are 1.169 and 1.005, respectively. The acid decomposition rates of Al-13 and Al-30 increase slightly when the temperature increases from 20 to ca. 35 A degrees C, but decrease when the temperature increases further. Al-30 is more stable than Al-13 in acidic solution, and the stability difference increases as the pH decreases. Al-30 is more possible to become the dominant species in polyaluminum coagulants than Al-13. The acid catalyzed decomposition and followed by recrystallization to form bayerite is one of the main processes that are responsible for the decrease of Al-13 and Al-30 in polyaluminum coagulants during storage. The deprotonation and polymerization of Al-13 and Al-30 depend on solution pH. The hydrolysis products are positively charged, and consist mainly of repeated Al-13 and Al-30 units rather than amorphous Al(OH)(3) precipitates. Al-30 is less stable than Al-13 upon alkaline hydrolysis. Al-13 is stable at pH < 5.9, while Al-30 lose one proton at the pH 4.6-5.75. Al-13 and Al-30 lose respective 5 and 10 protons and form [Al-13] (n) and [Al-30] (n) clusters within the pH region of 5.9-6.25 and 5.75-6.65, respectively. This indicates that Al-30 is easier to aggregate than Al-13 at the acidic side, but [Al-13] (n) is much easier to convert to Alsol-gel than [Al-30] (n) . Al-30 possesses better characteristics than Al-13 when used as coagulant because the hydrolysis products of Al-30 possess higher charges than that of Al-13, and [Al-30] (n) clusters exist within a wider pH range.

Guiding mode in elliptical core microstructured polymer optical fiber

A kind of microstructured polymer optical fiber with elliptical core has been fabricated by adopting in-situ chemical polymerization technology and the secondary sleeving draw-stretching technique. Microscope photography demonstrates the clear hole-structure retained in the fiber. Though the holes distortion is visible, initial laser experiment indicates that light can be strongly confined in the elliptical core region, and the mode field is split obviously and presents the multi-mode characteristic. Numerical modeling is carried out for the real fiber with the measured parameters, including the external diameter of 150 pin, the average holes diameter of 3.3 mu m, and the average hole spacing of 6.3 mu m. by using full-vector plane wave method. The guided mode fields of the numerical simulation are consistent with the experiment result. This fiber shows the strong multi-mode and weak birefringence in the visible and near-infrared band, and has possibility for achieving the fiber mode convertors, mode selective couplers and so on.

Casting preforms for microstructured polymer optical fibre fabrication

A monolithic structured polymer preform was formed by in-situ chemical polymerization of high-purity MMA monomer in a home-made mould. The conditions for fabrication of the preforms were optimized and the preform was drawn to microstructured polymer optical fibre. The optical properties of the resultant elliptical-core fibre were measured. This technique provides advantages over alternative preform fabrication methods such as drilling and capillary stacking, which are less suitable for mass production. (c) 2006 Optical Society of America.

RAFT调控的丙烯腈可控/活性自由基聚合研究

可逆加成裂解链转移(RAFT)聚合已经成为高分子合成的研究热点之一，这是因为它同时具有自由基聚合和活性聚合的优点，能够有效控制分子量和分子量分布，反应条件温和，可用于本体、溶液、悬浮、乳液等体系，单体范围广，能够合成嵌段、接枝、支化等复杂结构的聚合物。在已经报道的丙烯腈RAFT聚合研究中，所得聚合物具有较窄的分子量分布，分子量接近理论预测值，然而，最高值只达到5000左右。本论文的研究工作正是从这一个基本问题展开的。 1. 利用三硫代碳酸二苄基酯代替二硫代羧酸酯作为链转移剂，降低中间态自由基断裂反应的活化能，保证活性态与休眠态之间的平衡以一较快的交换速率进行，聚合结果表明，在文献报道的反应条件下，聚合速率有了明显的提高，同时聚合以一种可控的方式进行，所得聚合物分子量最高达8000，且分子量分布较窄。 2. 将二硫代苯甲酸异丙腈酯调控的丙烯腈聚合实验参数优化，提高反应温度降低缓聚，选择碳酸乙二酯作为溶剂减小链转移反应，导致中间态自由基断裂反应的效率大大提高，以一种可控/活性自由基聚合方式进行，首次合成了分子量高达32800、分子量分布指数小于1.3的聚丙烯腈。 3. 由于RAFT试剂很难制备和长期保存，当以二硫代物作为替代的调控试剂, 偶氮二异丁腈作为引发剂，可以在“原位”合成RAFT聚合所需的链转移剂，直接调控丙烯腈的自由基聚合，得到高分子量、分子量分布指数比较小的丙烯腈均聚物和共聚物。 4. 将不对称的双乙烯基单体作为支化剂引入到丙烯腈聚合体系中，同时采用RAFT技术来抑制交联反应，单体转化率增加至较高值而不形成凝胶，1H NMR和凝胶渗透色谱证明了合成的聚合物具有支化结构，并且聚合物的特性粘数低于相近分子量的线性聚合物的对应值。

含氮氧磷多齿配体稀土烷基配合物的合成、表征及催化丙交酯聚合

1. 合成了三齿水杨醛稀土配合物，发现配体中含有柔性取代基易生成均配物，而刚性较强的配体生成单烷基配合物。考察了单体浓度、聚合时间等因素对配合物催化丙交酯聚合活性的影响。 2. 以含二苯基膦苯胺的β-二酮单亚胺三齿配体合成了双配体单烷基稀土配合物，空间位阻比较大，因而引发丙交酯聚合的速度比较快。 3. 合成了含甲氧基侧基的芳氧胺四齿双烷基配合物，并合成了芳氧胺与茂（茚）混配的稀土单烷基配合物。首次将它们用于丙交酯的聚合，实验结果发现，双烷基配合物中的双烷基是作为双活性中心起作用的。 4. 合成了含双吡咯烷的稀土烷基配合物，将之应用于丙交酯的聚合，发现位阻大的配合物催化聚合可控性好。并应用双吡咯烷配合物进行了丙交酯和己内酯的共聚合研究。

水凝胶的制备及壳聚糖的改性和应用

水凝胶用作创口敷料时有很多的优点。壳聚糖是天然的阳离子多糖,已经在很多领域得到了应用。我们制备了几种具有抑菌能力的水凝胶敷料，同时利用可生物降解聚酯和多聚肽对壳聚糖进行了修饰，得到了一些新的结果。 本论文的工作主要包括以下两部分： 一.含有抗生素或纳米银粒子的水凝胶的制备和表征。 1．载药聚乙烯醇/聚乙烯基吡咯烷酮/壳聚糖（PVA-PVP-Chitosan）复合水凝胶的制备和抑菌性能评价。采用循环冷冻－熔融与辐射交联相结合的方法制备出了PVA-PVP-chitosan复合水凝胶，测定了凝胶的溶胀率、凝胶含量、力学强度和结晶性能，并考察了所用壳聚糖分子量，冷冻－熔融循环处理次数和辐射剂量对凝胶性能的影响。然后通过溶胀法将抗生素（环丙沙星）和壳寡糖载入水凝胶中，考察了它们的体外释放行为。同时利用琼脂糖平板法检验了载药凝胶的抑菌能力，结果表明它们可以有效抑制革兰氏阳性菌和革兰氏阴性菌的繁殖和生长。 2．含纳米银-PVA-PVP水凝胶的制备和抑菌性能评价。通过循环冷冻－熔融法制备了含银的PVA-PVP复合水凝胶。以含银的PVA-PVP复合膜为模型，利用DSC、红外光谱、紫外－可见光谱和X-射线衍射考察了掺入的纳米银与PVA-PVP网络的相互作用。利用扫描电镜观察了PVA-PVP凝胶的网络结构和银纳米粒子在网络中的分布。利用琼脂糖平板法和LB肉汤法对含银PVA-PVP凝胶的抑菌性能进行了评价，结果证明这种水凝胶可以有效抑制大肠杆菌和金黄色葡萄球菌的生长和繁殖。 二. 壳聚糖的改性和应用。 1．发展了一种制备聚ε－己内酯（PCL）接枝壳聚糖共聚物的新方法，并且由合成的接枝共聚物在水中自组装得到纳米粒子。利用DLS、AFM和SEM对纳米粒子进行了表征，结果显示制备的纳米粒子为圆球形或椭圆形。利用茚三酮显色法准确测定了活性胺基的含量，发现纳米粒子表面活性胺基的数量可以通过改变PCL接枝度进行调节。 2．由6-O-三苯甲基壳聚糖引发赖氨酸NCA的开环聚合得到了聚赖氨酸（PLL）接枝壳聚糖阳离子共聚物。利用红外光谱、核磁共振和GPC对接枝共聚物的分子结构和分子量进行了表征。通过动态光散射测量发现接枝共聚物可以和小牛胸腺DNA形成粒径在100~340 nm之间的复合物。凝胶阻滞电泳证明接枝共聚物对质粒DNA的结合和保护能力要优于壳聚糖。细胞转染实验证明接枝共聚物对293T和Hela细胞的转染效率要远远高于壳聚糖原料和PLL。同时，接枝共聚物的转染效率对PLL的聚合度有明显的依赖性，增加PLL聚合度有助于提高接枝共聚物的转染效率。这种新型的阳离子接枝共聚物有望用作高效基因载体。