Detection of the effect of environmental toxicants on the synthetic peptide modified neural cell chip

A cell based chip was designed to differentiate and to detect the effects of environmental chemicals on the neurite outgrowth in PC12 cell. To fabricate platform of cell chip, gold surfaces were modified by RGD based synthetic oligopeptide. Nanoscale controlled self-assembled peptide layer was investigated by Atomic Force Microscopy (AFM). On the fabricated cell chip, PC12 cell was immobilized and the differentiation of neurite outgrowth in PC12 cells was done by neurite growth factor (NGF). Differentiation of PC12 cell was confirmed by immunofluorescence study. Further the differentiation and the length of neurite was confirmed by confocal microscopy study. Voltammetry behavior of the neurite induced PC12 and the electrochemical behavior of the environmental toxicants effect on the neurite outgrowth was measured by cyclic voltammetry (CV). Self-assembled layer mediated cell immobilization technique and voltammetric signal analysis system can be applied to construct the neural cell chip for the detection of large number of environmental toxins and various neurotoxicants.     

Cell chip with nano-scale peptide layer to detect dopamine secretion from neuronal cells

A cell chip with a nano-scaled thin film of cysteine modified synthetic oligopeptide C(RGD)4 was fabricated to detect dopamine secretion from neuronal cells. Thin C(RGD)4 peptide layer was fabricated on chip surface for increasing the binding affinity of cells to gold electrode surface, which is essential for the electrochemical detection of dopamine released from PC12 cells. The structural formation of the peptide thin film was confirmed by both atomic force microscopy (AFM) and scanning electron microscopy (SEM). Redox characteristics of chemical dopamine were firstly characterized by voltammetric tool to compare the dopamine released from PC12 cells. Cells grown on the chip were then subjected to cyclic voltammetric (CV) analysis after 48 hours of incubation. The intensities of reduction peaks were found to be increased with increasing the concentrations of PC12 cells. In addition, the electrochemical redox signal increased more in the cells treated with glucose and potassium compared to the control group. Hence, the developed cell chip can be used to determine the effects of drugs on living cells electrochemically.     

Cell chip to detect effects of graphene oxide nanopellet on human neural stem cell

The graphene oxide (GO) nanopellet, a potentially useful carbon-based material, recently started being applied in cell-based research areas. Its toxicity assessment using the neural-stem-cell-based chip has not been thoroughly reported yet, though. Herein, a cell chip was fabricated to electrochemically detect the toxic effects of GO nanopellets on HBl.F3 cells. The RGD peptide was immobilized on the gold electrode surface to enhance the binding affinity of the HBl.F3 cells to the electrode surface. A clear redox peak appeared when the HB1.F3 cells were analyzed via cyclic voltammetry. The GO nanopellet was analyzed via Raman spectroscopy to confirm its distinct structural characteristics that normally differ from those of graphite oxide. After GO was added to the HB1.F3 cells, differential pulse voltammetry was performed to discover the toxic effects of GO nanopellets on HB1.F3 cells. A negative correlation was achieved between the concentration of the GO nanopellets and the cell viability, which was verified via both MTT assay and a microscopic imaging tool. Thus, these electrochemical tools can be usefully applied to the toxicity assessment of various kinds of carbon-based materials.     

Fabrication of nanoconcave surface for cell immobilization in cell-based chip

Nanostructured surface such as nanoconcave shape can be utilized as a bioplatform to immobilize cells. In this study, we present fabrication of Au-coated nanoconcave surface and some possibility of cell immobilization. Long-range ordered periodic patterns with concave shape were formed on aluminum substrate by electrochemical anodization process. The morphology and topography of nanoconcave surface was investigated by atomic force microscopy and scanning electron microscopy. The pore-pore distance and the pore depth of nanoconcave pattern were measured at 105 +/- 5 nm and 30 +/- 2 nm, respectively. After Au deposition, the pore depth within Au-coated concave surface was 15 +/- 2 nm. The topography of HeLa cells immobilized on the nanoconcave surface was observed by AFM combined with confocal microscopy. The result expected that the Au-coated nanoconcave surface may be used as new culture substrate for cells immobilization in cell-based chip.     

Bipartite design of a self-fibrillating protein copolymer with nanopatterned peptide display capabilities

The development of biomatrices for technological and biomedical applications employs self-assembled scaffolds built from short peptidic motifs. However, biopolymers composed of protein domains would offer more varied molecular frames to introduce finer and more complex functionalities in bioreactive scaffolds using bottom-up approaches. Yet, the rules governing the three-dimensional organization of protein architectures in nature are complex and poorly understood. As a result, the synthetic fabrication of ordered protein association into polymers poses major challenges to bioengineering. We have now fabricated a self-assembling protein nanofiber with predictable morphologies and amenable to bottom-up customization, where features supporting function and assembly are spatially segregated. The design was inspired by the cross-linking of titin filaments by telethonin in the muscle sarcomere. The resulting fiber is a two-protein system that has nanopatterned peptide display capabilities as shown by the recruitment of functionalized gold nanoparticles at regular intervals of ～ 5 nm, yielding a semiregular linear array over micrometers. This polymer promises the uncomplicated display of biologically active motifs to selectively bind and organize matter in the fine nanoscale. Further, its conceptual design has high potential for controlled plurifunctionalization.     

Fabrication of cell chip for detection of cell cycle progression based on electrochemical method

A new strategy for on-site monitoring of cell cycle progression was proposed using cell chip technology. Cell synchronization has been utilized in intensive cellular research due to the fact that cells in different phases of the cell cycle exhibit different behaviors even when exposed to the same concentrations of drugs or toxicants. However, confirmation of cell cycle arrest in research is usually dependent on fluorescence-assisted cell sorting (FACS), which is laborious, time-consuming, and expensive. In this study, we employed a cell-chip-based electrochemical method to detect the cell-cycle-dependent electrochemical properties of cells. Electron transfer at the cell-electrode interface played a key role in our strategy and accurately reflected the redox activity of the cells in different phases. Rat pheochromocytoma cells were synchronized with thymidine and nocodazole, and well-defined current peaks from cells in the G1/S- and G2/M-phases were significantly different as determined by differential pulse voltammetry. FACS assay and Western blot analysis were used to validate the electrochemical findings. Hence, our cell-chip-based electrochemical method can be a useful tool in determining cell cycle progression easily and economically.     

环烯烃聚合物(COP)微流控芯片的制备及其与聚甲基丙烯酸甲酯(PMMA)微流控芯片的性能对比

采用热压方法制备了环烯烃聚合物(COP)微流控芯片.考虑到温度对微结构热压成形的质量影响最大,基于材料的粘弹性特性,通过变温准蠕变实验获得了热压参考温度Tr.实验证明,在该温度下热压成形,宽度和深度方向的复制精度分别达到了97.6%和94.3%.为了研究制备的COP微流控芯片的性能,将其和同一模具制备的PMMA微流控芯片进行了性能对比实验.通过背景荧光实验、电泳实验和DNA分析实验三方面的研究表明,与PMMA芯片相比,COP芯片背景荧光低,电泳效率高,检测重现性相对标准偏差小于2.5%,适用于生化分析.     

Ceramic nanopatterned surfaces to explore the effects of nanotopography on cell attachment

Surfaces with ordered, nanopatterned roughness have demonstrated considerable promise in directing cell morphology, migration, proliferation, and gene expression. However, further investigation of these phenomena has been limited by the lack of simple, inexpensive methods of nanofabrication. Here, we report a facile, low-cost nanofabrication approach based on self-assembly of a thin-film of gadolinium-doped ceria on yttria-stabilized zirconia substrates (GDC/YSZ). This approach yields three distinct, randomly-oriented nanofeatures of variable dimensions, similar to those produced via polymer demixing, which can be reproducibly fabricated over tens to hundreds of microns. As a proof-of-concept, we examined the response of SK-N-SH neuroblastoma cells to features produced by this system, and observed significant changes in cell spreading, circularity, and cytoskeletal protein distribution. Additionally, we show that these features can be imprinted into commonly used rigid hydrogel biomaterials, demonstrating the potential broad applicability of this approach. Thus, GDC/YSZ substrates offer an efficient, economical alternative to lithographic methods for investigating cell response to randomly-oriented nanotopographical features.     

Application of the thermally tuned tandem column concept to the separation of several families of environmental toxicants

Separations of several families of environmental toxicants were optimized by means of the thermally tuned tandem column (T3C) concept. We use a tandem combination of an octadecylsilane (ODS) and a carbon-coated zirconia (C-ZrO2) column; and tune the selectivity by independently adjusting the isothermal temperatures of the two columns. This results in the change in the contribution that each column makes to the overall retention and selectivity. The separation was optimized by locating the optimum pair of column temperatures which give the best separation of the critical solute pair. For both triazine herbicides and carbamate pesticides samples, dramatically different selectivities and different critical pairs were observed for the two types of phases. Although neither individual phase gave adequate separation, the T3C approach provided baseline separations using only four preliminary trial separations. We also showed that, for the triazine samples, the T3C approach gave a better separation than did conventional mobile phase optimization with an ODS column. The combination of superior selectivity of T3C and high flow rate allows the baseline separation of complex mixtures in just a few minutes.     

Fabrication of gold nanoparticle modified ITO substrate to detect beta-amyloid using surface-enhanced Raman scattering

Alzheimer's disease is a progressive neurodegenerative disorder that is characterized by the deposition of beta-amyloid (Abeta) peptide and the formation of neurofibrillary tangles in neurons. The Abeta peptide is a key molecule in the pathogenesis of Alzheimer's disease and an important marker for early diagnosis. Surface-enhanced Raman scattering (SERS) has recently been attracting keen interest in various fields such as for biosensors or immunoassays. In this study, gold nanoparticles (Au NPs) were electrochemically deposited on an indium tin oxide (ITO) substrate at different heights. Abeta antibodies were immobilized on the Au-NP-coated ITO substrate, after which the interactions between the antigen and the antibody were determined via SERS spectroscopy. The SERS responses were strongest at the Au NP array height of 91 nm, with a good linear relationship that corresponded to the change in the concentration of the antigen. This Au-NP-array-mediated SERS can be applied with a highly sensitive immunodetection biosensor.     

Fabrication of a nanocrystalline Cr–C layer with excellent anti-wear performance

Nanocrystalline Cr–C layers with excellent anti-wear performance were prepared by electrodeposition in Cr³⁺ bath and subsequent annealing. X-ray diffraction (XRD) shows that the crystalline structure of the Cr–C layer changed from amorphous to nanocrystalline when the annealing was conducted. The hardness, Young's modulus and wear rate of the Cr–C layer were measured. The results indicate that the 400 °C-annealed nanocrystalline Cr–C layer exhibits a high ratio of hardness to Young's modulus and excellent wear resistance. The excellent wear resistance can be attributed to the proper compromising of hardness and toughness. The friction tests reveal that the friction coefficient depends on the Young's modulus and the counterpart. Comparing wear with friction, no obvious connection can be found between them.     

旋转摩擦挤压加温法制备金刚石表面Ti涂层

为了实现金刚石表面金属化,提出了一种旋转摩擦挤压加温法在人造单晶金刚石表面制备Ti涂层.利用SEM和XRD,分析了Ti涂层内表面的微观形貌和界面间的物相组成,并采用能谱仪进行了元素分析,研究了扩散退火温度和保温时间对Ti涂层内表面物相组成的影响,并分析了金刚石/Ti涂层的界面形成机制.研究结果表明:经过旋转摩擦挤压涂覆...     

Comparison of mesenchymal stem cell and osteosarcoma cell adhesion to hydroxyapatite

Immortalized cells are often used to model the behavior of osteogenic cells on orthopaedic and dental biomaterials. In the current study we compared the adhesive behavior of two osteosarcoma cell lines, MG-63 and Saos-2, with that of mesenchymal stem cells (MSCs) on hydroxyapatite (HA). It was found that osteosarcoma cells demonstrated maximal binding to fibronectin-coated HA, while MSCs alternately preferred HA coated with collagen-I. Interesting, the binding of MG-63 and Saos-2 cells to fibronectin was mediated by both α5 and αv-containing integrin heterodimers, whereas only αv integrins were used by MSCs. Cell spreading was also markedly different for the three cell types. Osteosarcoma cells exhibited optimal spreading on fibronectin, but poor spreading on HA disks coated with fetal bovine serum. In contrast, MSCs spread very well on serum-coated surfaces, but less extensively on fibronectin. Finally, we evaluated integrin expression and found that MSCs have higher levels of α2 integrin subunits relative to MG-63 or Saos-2 cells, which may explain the enhanced adhesion of MSCs on collagen-coated HA. Collectively our results suggest that osteosarcoma cells utilize different mechanisms than MSCs during initial attachment to protein-coated HA, thereby calling into question the suitability of these cell lines as in vitro models for cell/biomaterial interactions.     

Fabrication and performance comparison of planar and sandwich structures of micro-bolometers with Ge thermo-sensing layer

Two types of micro-bolometer structures were fabricated with the same materials and fabrication process. The structures are labeled planar and sandwich types. Their performance was measured and a comparison was performed among these structures. Our results show that the sandwich type structure behaves better in terms of the voltage and current responsivity, but shows 2 to 3 orders of magnitude higher 1/f noise levels. In spite that the sandwich configuration shows a lower response time constant than that of the planar device, the noise level makes the detectivity of both devices practically the same.     

离子交换法制备聚酰亚胺/氧化铝复合薄膜及性能研究

采用离子交换技术以氯化铝溶液为铝源制备出了上下两个表层含氧化铝的聚酰亚胺/氧化铝(PI/Al2O3)复合薄膜。对制备的复合薄膜的形貌、力学性能、热性能和电性能进行了表征和测试,并与纯PI薄膜进行了对比。扫描电镜(SEM)结果显示复合薄膜表面无可见粒子,能谱(EDS)显示复合薄膜表面含有Al元素;力学测试结果显示复合薄膜基本上维持了纯膜优越的力学性能;热失重(TG)表明复合薄膜比纯膜有更好的热稳定性;击穿场强测试结果表明复合薄膜击穿场强由原纯膜的291kV/mm提高到了303kV/mm;耐电晕测试结果表明复合薄膜的耐电晕时间由原纯膜的8min提高到了53min,比原纯膜有了很大提升。     

Zn层添加AZ31/7075合金复合成形工艺及组织与性能研究EI北大核心CSCD

通过在异种材料界面添加厚度为100μm的Zn箔,采用预挤压与孔型轧制复合工艺成功制备出AZ31/7075复合材料,并利用光学显微镜(OM)、扫描电子显微镜(SEM)、能谱分析(EDS)对复合界面进行表征及显微硬度测试,探究Zn过渡层在挤压复合孔型轧制过程中对产品的影响。结果表明:7075硬质铝合金芯部可细化AZ31镁合金,引入Zn过渡层可减少或者避免镁铝系金属间化合物生成;挤压及变形温升使Mg-Zn互扩散形成的低熔点共晶相熔化,同时加速元素自固相向液相扩散;然而降温冷却使Mg-Zn扩散层易出现不连续裂缝,但后续孔型轧制可显著改善;Mg-Zn扩散层经变形生成的MgZn_(2)金属间化合物具备较高的显微硬度(161HV),但Mg-Zn扩散层变形后厚度则较薄,结合层整体硬度变化不明显。     

Fabrication of vertical ZnO nanowires on silicon (100) with epitaxial ZnO buffer layer

Vertical ZnO nanowires were successfully grown on epitaxial ZnO (002) buffer layer/Si (100) substrate. The nanowire growth process was controlled by surface morphology and orientation of the epitaxial ZnO buffer layer, which was deposited by radio-frequency (rf) sputtering. The copper catalyzed the vapor-liquid-solid growth of ZnO nanowires with diameter of approximately 30 nm and length of approximately 5.0 microm. The perfect wurtzite epitaxial structure (HCP structure) of the ZnO (0002) nanowires synthesized on ZnO (002) buffer layer/Si (100) substrate results in excellent optical characteristics such as strong UV emission at 380 nm with potential use in nano-optical and nano-electronic devices.     

Fabrication of a microfluidic chip containing dam,weirs and gradient generator for studying cellular response to chemical modulation

A microfluidic chip was designed and fabricated for studying cellular response to chemical modulation. The microfluidic network comprised an up-stream gradient-generating module and a down-stream cell culture module. The microchip was composed of a piece of glass plate and a covered PDMS film. By using a two-step wet etching method, the dam structure was fabricated on the inlet of the cell chamber facilitating cell positioning, and a series of weir structures were fabricated on the bottom of cell culture reservoirs facilitating cell seeding. This microfluidics exploited the advantage of lab-on-a-chip technology by integrating the generation of chemical concentration gradients and a series of cell operations including seeding, culture, stimulation and staining into a chip. Steady concentration gradients were generated by flowing two fluids in the network. Over time observation showed that the microchip was suitable for cell seeding and culture. The microchip described above was applied in studying the roles of As₂O₃ and buthionine sulfoximine (BSO) in mediating intracellular levels of reduced glutathione (GSH) and reactive oxygen species (ROS) in MCF-7 cells. MCF-7 cells showed dose dependent reaction to the chemical modulations. Upon the treatment with both As₂O₃ and BSO, GSH levels were down-regulated but ROS levels were up-regulated. As₂O₃ showed a stronger effect on ROS enhancement, while BSO was more effective on GSH depletion. The integrated microfluidic chip is able to perform multiparametric pharmacological profiling with easy operation, thus holds great potential for extrapolation to the cell based high-content drug screening.     

Fabrication and characterization of twin poly-Si thin film transistors EEPROM with a nitride charge trapping layer

This study investigates the characteristics of the planar twin poly-Si thin film transistor (TFT) EEPROM that utilizes a nitride (Si3N4) charge trapping layer. A comparison is made of two devices with different gate dielectrics, one a 16 nm-thick oxide (SiO2) layer for O-structure and the other 5 nm/10 nm-thick oxide/nitride layers for O/N-structure. Incorporating a nitride charge trapping layer and reducing the tunneling oxide thickness enable the O/N-structure EEPROM to enhance the program/erase (P/E) efficiency. Additionally, EEPROM formed with the tri-gate nanowires (NWs) structure can further enhance P/E efficiency and a large memory window because of its high electric field across the tunneling oxide. Reliability results indicated that, since the nitride layer contains discrete traps, the memory window can be maintained 2.2 V after 10(4) P/E cycles. For retention, the memory window can be maintained 1.9 V, and 30% charge loss for ten years of data storage. This investigation indicates that its possibility in future system-on-panel (SOP) of thin-film transistor liquid crystal display (TFTLCD) and 3-D stacked high-density Flash memory applications.     

Robustness of differentiation cascades with symmetric stem cell division

Stem cells (SCs) perform the task of maintaining tissue homeostasis by both self-renewal and differentiation. While it has been argued that SCs divide asymmetrically, there is also evidence that SCs undergo symmetric division. Symmetric SC division has been speculated to be key for expanding cell numbers in development and regeneration after injury. However, it might lead to uncontrolled growth and malignancies such as cancer. In order to explore the role of symmetric SC division, we propose a mathematical model of the effect of symmetric SC division on the robustness of a population regulated by a serial differentiation cascade and we show that this may lead to extinction of such population. We examine how the extinction likelihood depends on defining characteristics of the population such as the number of intermediate cell compartments. We show that longer differentiation cascades are more prone to extinction than systems with less intermediate compartments. Furthermore, we have analysed the possibility of mixed symmetric and asymmetric cell division against invasions by mutant invaders in order to find optimal architecture. Our results show that more robust populations are those with unfrequent symmetric behaviour.