微载体技术肝细胞体外高密度培养的实验

将大鼠肝细胞接种至2种不同微载体(实体微载体Cytodex、多孔微载体Cytopore)进行微重力高密度体外培养,观察细胞生长形态及细胞活力等情况,并通过细胞代谢功能指标葡萄糖、白蛋白、尿素等指标的测定,反映细胞在两种载体的生长和代谢情况。结果表明,Cytopore的MTT值、代谢指标值是Cytodex的1倍左右。因此,大鼠肝细胞在载体Cytopore的高密度培养比载体Cytodex更有利于细胞的生长增殖和代谢。     

微载体技术肝细胞体外高密度培养的实验

将大鼠肝细胞接种至2种不同微载体(实体微载体Cytodex、多孔微载体Cytopore)进行微重力高密度体外培养,观察细胞生长形态及细胞活力等情况,并通过细胞代谢功能指标葡萄糖、白蛋白、尿素等指标的测定,反映细胞在两种载体的生长和代谢情况。结果表明,Cytopore的MTT值、代谢指标值是Cytodex的1倍左右。因此,大鼠肝细胞在载体Cytopore的高密度培养比载体Cytodex更有利于细胞的生长增殖和代谢。     

葡萄糖及其代谢产物对犬肾上皮-siat7e细胞生长代谢的影响

目的探讨葡萄糖及其代谢产物对转染siat7e基因的犬肾上皮(Madin-Darby canine kidney,MDCK)细胞(MDCKsiat7e)生长代谢的影响。方法采用含不同起始量(3. 86、6. 46、9. 29、10. 60、12. 80、16. 06 g/L)和维持量(3、5、7 g/L)葡萄糖浓度的无血清无蛋白培养基cellhappy BD001(简称BD001),分别分批培养MDCK-siat7e细胞,每24 h取样进行活细胞计数及葡萄糖、乳酸、氨含量测定。结果不同起始及维持量葡萄糖浓度的BD001对MDCK-siat7e细胞生长均无明显影响,细胞比生长速率以及乳酸、氨比生成速率和乳酸、氨含量差异均无统计学意义(P 0. 05)。结论葡萄糖并不是制约MDCK-siat7e细胞生长的重要因素,起始葡萄糖浓度较低时,细胞生长后期可能利用代谢副产物乳酸维持生长,而起始葡萄糖浓度较高时,代谢副产物乳酸则有可能抑制细胞的生长,氨对细胞的生长具有明显的抑制作用。     

在无血清培养基中代谢副产物对杂交瘤细胞生长代谢的影响:Ⅱ.氨的作用

目的 在无血清培养基中，研究氨对杂交瘤细胞生长代谢的影响。方法 在培养基中添加不同浓度的氨，考察细胞生长和代谢及单抗生成的变化。结果 添加0．8mmol/L）的氨时就对细胞生长和代谢有影响，当氨浓度达4mmol/L时，对细胞的生长代谢有明显的抑制，当培养基中氨浓度高于6mmol/L时，细胞生长停止，代谢受到严重影响。氨的添加降低了培养上清中的单抗浓度，但提高了单抗的比生产速率。结论 氨对细胞生长和代谢有较大的影响，对单抗浓度的影响主要由细胞密度降低造成，单抗的比生产速率增加。     

葡萄糖浓度对杂交瘤细胞代谢通量分布的影响

将代谢工程理论应用于动物细胞的流加培养过程。通过构建代谢网络模型，研究了杂交瘤细胞从动态到拟稳态过程中物质和能量代谢通量的时间分布图。结果表明：当葡萄糖浓度较高时，葡萄糖在乳酸生成途径和TCA循环的代谢通量分配比例分别为90%和10%，ATP生成的比例分别为20%和60%，说明葡萄糖大部分经糖酵解途径生成乳酸，而进入TCA循环的少量部分则提供大部分的能量生成。当葡萄糖浓度降至其限制细胞生长的浓度时，进入TCA循环的葡萄糖比例逐步提高到100%，葡萄糖的氧化程度从0. 6 mmol·mmol^-1增至4. 52 mmol·mmol^-1，说明葡萄糖代谢逐渐从乳酸生成途径迁移到TCA循环，从无氧代谢逐渐转移到有氧代谢。     

杂交瘤细胞流加培养中葡萄糖和谷氨酰胺的代谢控制

对底物限制的流加培养中杂交瘤细胞HB 58的生长、代谢和单抗生成进行了研究。葡萄糖或 谷氨酰胺限制引起比生长速率下降。葡萄糖限制时,乳酸生成减少,细胞对葡萄糖的得率增 加,乳酸对葡萄糖的得率降低,说明葡萄糖更多地参与三羧酸循环。谷氨酰胺限制时,氨和丙氨酸生成减少,细胞和氨对谷氨酰胺的得率增加,丙氨酸对谷氨酰胺的得率减小,说明谷氨酰胺更多地参与脱氢反应,其有效利用率得到提高。     

谷氨酰胺限制对杂交瘤细胞生长、代谢和单抗生产的影响

利用批培养和流加培养方式以及不同的流加培养成分,考察了谷氨酰胺限制对杂交瘤细胞生长、代谢和单抗生成的影响.谷氨酰胺限制降低了最大细胞密度和单抗比生产速率,说明谷氨酰胺限制阻碍了细胞生长和单抗生产.谷氨酰胺限制流加培养的YLac/Gluc和YLac/Cells高于批培养和谷氨酰胺非限制流加培养的,说明谷氨酰胺限制促进了葡萄糖向乳酸的生成,增强了葡萄糖的溢流代谢.与批培养和谷氨酰胺非限制流加培养相比,谷氨酰胺限制流加培养的氨和丙氨酸浓度及其比生成速率较低,而且YAmm/Gln高,YAla/Gln和YAla/Cells低,说明谷氨酰胺限制使得较多的谷氨酰胺参与脱氢反应,提高了谷氨酰胺的利用率,降低了细胞对氨和丙氨酸的生成,从而削弱了氨对细胞生长和单抗生产的毒害.在流加培养中应严格控制谷氨酰胺的流加浓度及与葡萄糖的配比,要避免谷氨酰胺过分限制导致的葡萄糖溢流代谢和对细胞生长和单抗产率的不利效应.     

rCHO细胞在葡萄糖限制流加培养过程中的生长与代谢特性

以调控rCHO细胞的葡萄糖代谢为主要研究目标,通过在2L生物反应器中进行的批培养和葡萄糖限制恒速流加培养的方法,考察了在培养过程中葡萄糖浓度对rCHO细胞生长、葡萄糖和谷氨酰胺消耗,以及副产物乳酸、氨和丙氨酸生成的影响.结果表明:葡萄糖限制的流加培养过程中,活细胞密度XV达到2.35(106cells(mL(1,较批培养提高一倍;而乳酸生成大幅减少.在葡萄糖限制培养阶段,qLac和YLac/Gluc持续降低至零,而qo2/qGluc由0.7 mmol(mmol(1上升至4.3mmol(mmol(1,说明更多葡萄糖进入高效释能代谢途径.同时谷氨酰胺的消耗增加,YAmm/Gln增大,YAla/Gln下降,证明谷氨酰胺的能量利用率也有所提高.     

酸胁迫作用下悬浮培养红豆杉细胞的磁场生物学效应

研究了直流稳恒磁场对酸胁迫作用下悬浮培养南方红豆杉细胞生长和代谢的影响. 结果表明,磁场提高了红豆杉细胞的抗酸胁迫能力,细胞活力上升,生物量和蛋白含量明显升高,胞外多酚氧化酶(PPO)活力升高,酚类物质积累受到抑制. 在一定浓度的盐酸作用下细胞受到的酸胁迫越大,磁场的生物学效应越明显. 胞外pH值和电导率的变化说明磁场提高细胞抗酸胁迫的能力与其加速了物质的跨膜转运有关.     

酿酒酵母单细胞生长动力学的初步研究

采用同步培养方法对酿酒酵母的单细胞生长动力学进行了初步研究.在Mitchison和Vincent梯度离心方法的基础上,改进了同步化方法.采用高效液相色谱(HPLC)法测定了菌体同步生长过程中体系各组份的变化情况,进一步得到了单个细胞的代谢动力学数据,包括葡萄糖的消耗和乙醇的产出,发现在一个细胞周期内的不同阶段,酿酒酵母的葡萄糖消耗速率与乙醇产出速率均呈明显的周期性.     

Low-voltage DC/AC electrolysis of water using porous graphite electrodes

Using DC and AC electrolysis of water, experimental current density-voltage curves were determined using graphite electrodes in an electrolyte of 5 mol of NaOH per liter. It was found that certain aspects of the DC curves could not be accounted for, using a model based on modern electrochemical theory. However, the experimental data could be explained using a revised model which incorporated the adsorption of hydrogen and oxygen by the graphite electrodes. The AC curves had to be explained via a more complex model based on current flowing in the outside circuit. During AC electrolysis, little or no gas was formed via current through the cell. If the electrodes are of a different area, hydrogen and oxygen are formed on the small-area electrode only at a relatively low potential; at a higher potential, both gases are formed at both electrodes. According to the model, the current does not cross the electrolysis cell either above or below the decomposition potential, but flows through the low-impedance outside circuit. Using these models, the experimental features of both DC and AC electrolysis of water can be explained.     

Long-term activity of covalent grafted biocatalysts during intermittent use of a glucose/O2 biofuel cell

The operational stability of enzymes in a concentric glucose/O₂ biofuel cell has been significantly improved with the synthesis of grafted enzyme electrodes compared to entrapped enzyme electrodes. The concentric device combined glucose electro-oxidation by glucose oxidase at the anode and oxygen electro-reduction by bilirubin oxidase at the cathode. The entrapped enzyme electrodes were prepared from physical immobilization of the enzymes by a polypyrrole polymer onto the electrode surface. The grafted enzyme electrodes were synthesized by grafting the enzymes via alkyl spacer arms to a poly(aminopropylpyrrole) film onto the electrode surface. From spectrophotometric and electrochemical analyses, it was demonstrated that the spacer arms increased the operational stability and enzyme mobility that favoured electron transfer from their active sites to the electrode.The maximum power output of the assembled biofuel cell was 20 μW cm⁻², at 0.20 V with 10 mM glucose in phosphate buffer pH 7.4. The grafted enzyme electrodes presented an unprecedented operational stability as the maximum of power density of the BFC remains constant after intermittent use over a 45-day period. This was a remarkable improvement compared to electrodes with entrapped enzymes, which lost 74% of their initial power density after intermittent use over a 17-day period.     

纳米银修饰电极的电化学性能初探

在圆柱形电解槽中,采用直流电沉积方法在导电玻璃上沉积银纳米材料,制备了Ag/I-TO、Ag/CNTs/ITO复合电极,并以制得的复合电极做工作电极,测定两种电极在磷酸缓冲溶液中的循环伏安响应曲线。CNTs具有很高的比表面积,除了对银离子的反应具有催化作用外,还可能对带有负电荷的SCN-离子具有吸附作用。实验结果表明：银修饰的碳纳米管导电玻璃电极具有很好的电化学活性,可用于检测SCN^-。     

不同熔炼工艺对电熔方镁石的影响

为了提高电熔方镁石品位,合理利用资源,以菱镁矿为原料制备电熔方镁石。研究了不同石墨电极（分别是直流空心电极、直流实心电极、交流空心电极和交流实心电极）对电熔方镁石的影响。通过对电熔方镁石的体积密度、显气孔率、物相组成和显微结构进行分析,结果表明：电熔方镁石坯体在靠近皮砂位置结晶最好,晶体发育比较完整;使用空心电极制备出的电熔方镁石结构致密,晶粒尺寸大。用交流空心电极制备出的电熔方镁石体积密度最大、显气孔率低、晶界平直,形成了较大尺寸的方镁石晶粒。     

The role of iron in the prevention of nickel electrode deactivation in alkaline electrolysis

There is some uncertainty concerning the role of iron deposits on the surface of nickel electrodes with respect to electrode activity during alkaline water electrolysis. Iron deposits variously have been reported to enhance nickel electrode activity by providing additional surface area from electrolytic deposition of solution phase iron species or to depassivate nickel electrodes via a surface interaction effect. In this study, nickel electrodes were sputtered with a smooth iron layer to determine the effect of metallic iron on the electrode surface without significantly changing the electrode surface area. A permeation cell with 8 mol/L KOH at 70 °C was used to follow nickel electrode potentials during hydrogen evolution while the permeation current was used to detect changes in the electrode structure.Short term measurements reveal no difference in behavior of coated and non-coated electrodes. Longer term results showed that a metallic iron coating on nickel electrodes prevented deactivation of the electrodes. The deactivation effect was associated with an increased hydrogen flux through the electrodes indicative of an elevated hydrogen concentration at the electrode surface. This high surface concentration is concluded to be the result of nickel hydride phase formation at the surface of the nickel electrodes. The iron coating prevents this surface phase from forming and hence prevents deactivation of the electrode.     

Approximate evaluation of cell resistance with resistive electrodes

The resistance of a cell composed of a resistive anode and a conductive cathode has been theoretically calculated by solving the two-dimensional Laplace equation for the solution phase where the anode has an overpotential of a linear type. Conditions were evaluated under which the cell resistance could be obtained on the assumption that the direction of the current flowing in solution was perpendicular to the electrode. These were not strongly dependent on the ratio of the interelectrode distance to the height of the electrodes. The main parameters which determine the conditions were the Wagner number and the ratio of the electrode resistance to the solution resistance.     

高氧超电极在电解法生产氯酸盐中的应用

制备了３种氧化涂层电极,分析了涂层物相组成、涂层形貌,测定了电极的电化学性能,研究了这些电极在电解法生产氯酸盐中的应用。结果表明：钌锡锑氧化物涂层电极具有较低析氯电位、较高析氧电位,电解ＮａＣｌ溶液生产ＮａＣｌＯ３具有较高电流效率。     

AC impedance studies on nickel oxide electrodes to determine self-discharge characteristics of Ni-H2 batteries

AC impedance measurements were made on nickel oxide electrodes in an alkaline medium. The electrodes were prepared by electrodeposition of nickel oxide on nickel foils from a nickel nitrate solution. The main purpose of the investigation was to determine the dependence of impedance parameters on the state of charge of the electrode. The results demonstrated that the current phase shift and impedance modulus vary linearly with state of charge at low frequencies. Hence, the state of charge can be estimated from the values of phase shift and modulus. The state of charge of nickel electrodes exposed to argon and hydrogen was determined at various time intervals. It was found that the electrode exposed to hydrogen discharged faster than that exposed to argon, indicating that hydrogen enhances the self-discharge rate of nickel oxide electrodes.     

Membrane-assisted capacitive deionization: Effect of Poly(vinyl alcohol) cross-linking on the properties of ion exchange membranes

Novel composite electrodes were developed for application in membrane capacitive deionization (MCDI). Activated carbon (AC) was dispersed in a solution of poly(vinyl alcohol) (PVA) mixed with polyacrylic acid (PAA) or poly dimethyl diallyl ammonium chloride (PDMDAAC), and cast onto the surface of an AC-based modified graphite electrode, prepared by phase inversion, to form a composite membrane further cross-linked with glutaraldehyde (GA). The effect of the cross-linking on the chemical structure of the PVA-based membranes was determined by attenuated total reflectance Fourier-transform infrared (ATR-FTIR) spectroscopy. Cyclic voltammetry was conducted to examine the specific capacitance of the composite electrodes. Desalination experiments were then performed with MCDI unit cells to study the effect of cross-linking on the desalination efficiency. It was proved that after optimization, the synthesized composite electrodes exhibited one and a half times higher NaCl removal capacity and three times higher adsorption rate as compared to that of a conventional CDI cell using commercial ion exchange membranes (IEMs) with almost the same energy consumption. The enhanced desalination performance was attributed to the optimized properties of the selected polymers and the improved adhesion of IEMs to the electrodes. This research paves the way for the application of new materials in MCDI processes for improved water desalination.     

Aging of electrochemical double layer capacitors with acetonitrile-based electrolyte at elevated voltages

Laboratory-scale electrochemical capacitor cells with bound activated carbon electrodes and acetonitrile-based electrolyte were aged at various elevated constant cell voltages between 2.75 V and 4.0 V. During the constant voltage tests, the cell capacitance as well as the capacitance and resistance of each electrode was determined. Following each aging experiment, the cells were analyzed by means of electrochemical impedance spectroscopy, and the individual electrodes were characterized by gas adsorption and X-ray photoelectron spectroscopy. At cell voltages above 3.0 V, the positive electrode ages much faster than the negative. Both the capacitance loss and resistance increase of the cell could be totally attributed to the positive electrode. At cell voltages above 3.5 V also the negative electrode aged significantly. X-ray photoelectron spectroscopy indicated the presence of degradation products on the electrode surface with a much thicker layer on the positive electrode. Simultaneously, a significant decrease in electrode porosity could be detected by gas adsorption.