链缠结对等规聚苯乙烯结晶的影响

在1×10^－3～2×10^－5 g•mL^－1溶液浓度范围内, 用溶液雾化冷冻升华法制备了等规聚苯乙烯(i-PS)的单链、寡链非晶态聚集体. 随着溶液浓度降低, i-PS分子链团间的分离程度增大, 链间缠结随之减少, 因此冷冻升华制备的样品中单、寡链线团数目逐渐增多. DSC研究结果表明随着溶液浓度的降低, 冷冻升华样品的结晶温度逐渐降低; 等温结晶得到的晶粒熔点和结晶度降低. 由浓度为2×10^－5 g•mL^－1溶液制备的i-PS样品在468.3 K熔体结晶60 min后, 得到平均体积约为1.5×10⁴ nm³的单链晶粒. 用SEM观察到晶粒尺寸约为20～50 nm. 采用偏光显微镜(POM)测量了不同温度等温时i-PS单、寡链聚集体球晶的生长速率. 用Hoffmann理论进行了描述, 计算得到了i-PS单链聚集体熔体结晶片晶的端表面能(σ_e)为30.2 erg•cm^－2, 侧表面能(σ)为5.7 erg•cm^－2及单分子链折叠功(q)约为4.5×10^－13 erg•molecule^－1. 与文献值相比, 实验结果表明链缠结对聚合物结晶有很大影响.     

纳米Eu2O3对HEK-293T细胞的生物活性影响

稀土化合物的生物效应研究已经引起广泛关注. 利用激光共聚焦显微镜观察到纳米Eu₂O₃能进入活HEK-293T细胞中且位于细胞核周围. 在体外培养条件下, 利用流式细胞仪法检测了纳米Eu₂O₃对细胞的活力及对细胞周期的影响, 结果表明当纳米颗粒浓度小于200 μg•mL^－1时, 对细胞活性没有明显影响; 而当纳米颗粒浓度≥400 μg•mL^－1时, 对细胞活性明显抑制. 当Eu₂O₃纳米颗粒在低浓度范围(≤50 μg•mL^－1)时对细胞周期基本没有影响, 而高浓度(≥200 μg•mL^－1)时对细胞周期均有显著抑制, 停滞在DNA合成后期. 这些研究结果均表明纳米Eu₂O₃对HEK-293T细胞具有明显的生物效应.     

高效液相色谱化学发光法检测牛奶中残留四环素类化合物的研究

基于四环素类抗生素药物中的四环素(TC)、土霉素(OTC)、金霉素(CTC)和多西环素(DC)能够强烈增敏通过恒电流电解方法在线电生BrO^－和鲁米诺之间产生的化学发光, 提出了一种高效液相色谱(HPLC)化学发光(CL)法检测4种四环素类抗生素药物的新方法. 以Nucleosil RP-C₁₈ (250 mm×4.6 mm, i.d., 5 μm, pore size, 100 Å)为色谱柱, 0.05 mol• L^－1磷酸二氢钾(pH 2.5)-乙腈(30∶70, V∶V)为流动相, 流速1.2 mL/min, 柱温25 ℃, 同时分离检测四种抗生素的总时间为11 min. 研究并优化了流动相、电生试剂化学发光检测的条件. 四种抗生素的检出限为0.002～0.008 μg•mL^－1 (3σ), 对0.01 μg•mL^－1的四种抗生素测定的相对标准偏差为2.0%～3.6% (n＝11). 该方法已成功应用于牛奶中残留四环素类抗生素含量的分析.     

一种简便灵敏测定C反应蛋白的免疫共振散射光谱分析新方法

在pH 6.0的柠檬酸-Na₂HPO₄缓冲溶液中及PEG-6000存在下, C反应蛋白(CRP)与羊抗人C反应蛋白可聚集形成免疫复合物微粒, 在350, 390, 440 nm处有三个共振散射峰. 激光散射法测得免疫复合物微粒的平均粒径为1720.0 nm. 在最佳实验条件下, CRP浓度在0.03～1.80 μg•mL^－1的范围内与390, 440 nm处共振散射强度都呈良好的线性关系, 其回归方程、相关系数、检出限分别为ΔI_{390 nm}＝306.4c＋17.3, ΔI_{440 nm}＝296.0c＋10.7; 0.9993, 0.9996; 0.011, 0.012 μg•mL^－1. 该方法选择性较好, 操作简便, 用于人血清中C反应蛋白的测定, 结果与免疫透射比浊法结果一致, 相对标准偏差在0.90%～4.12%.     

基于聚硫堇、DNA/纳米银复合物共修饰癌胚抗原免疫传感器的研究

将硫堇聚合到玻碳电极(GCE)表面形成带正电的多孔聚硫堇(PTH)复合膜, 通过静电吸附固定DNA/纳米银复合物, 利用复合物中纳米银大的比表面积和强的吸附能力将癌胚抗体(anti-CEA)固定到电极表面, 从而制得高灵敏的电流型癌胚抗原(CEA)免疫传感器. 通过循环伏安法考察了电极表面的电化学行为, 并对免疫传感器的性能进行了详细研究. 在最优的实验条件下, 用示差脉冲伏安法(DPV)对癌胚抗原进行检测, 其线性范围为1.0～10.0 ng•mL^－1和10.0～80.0 ng•mL^－1, 线性相关系数分别为0.9983和0.9970, 检测限为0.24 ng•mL^－1, 并将该免疫传感器用于血清样品中CEA的检测.     

百草枯与牛血清白蛋白结合作用的荧光光谱

在模拟动物体生理条件下, 用荧光光谱和紫外-可见吸收光谱法研究了在不同温度下, 百草枯(PQ)与牛血清白蛋白(BSA)结合反应的光谱行为. 试验发现, PQ对BSA有较强的荧光猝灭作用. 用Stern-Volmer和Lineweaver-Burk方程分别处理试验数据, 发现BSA与PQ发生反应生成了新的复合物, 属于静态荧光猝灭, 发生分子内的非辐射能量转移. 根据F?rster的偶极-偶极非辐射能量转移理论计算出结合位置距离212位色氨酸残基2.07 nm. 由Lineweaver-Burk方程求出了不同温度下反应时复合物的形成常数K_LB (297 K: 2.035×10⁴ L•mol^－1; 304 K: 3.256×10⁴ L•mo^－1; 311 K: 2.889×10⁴ L•mol^－1)及对应温度下结合反应的热力学参数(⊿H^Ø＝18.50 kJ•mol^－1;⊿S^Ø＝144.7 J•K^－1/145.2 J•K^－1/141.0 J•K^－1; ⊿G^Ø＝－24.50 kJ•mol^－1/－25.66 kJ•mol^－1/－25.36 kJ•mol^－1), 证明二者主要靠疏水作用力结合. 同时用三维荧光光谱及同步荧光光谱法探讨了PQ对BSA构象的影响, 为预防和医治PQ中毒提供了重要依据.     

基于辣根过氧化物酶/纳米金/辣根过氧化物酶/多壁纳米碳管修饰的过氧化氢生物传感器的研究

以固定在玻碳电极上的多壁纳米碳管为基底吸附辣根过氧化物酶, 再固定纳米金, 然后再结合一层辣根过氧化物酶, 利用多壁纳米碳管对辣根过氧化物酶的直接电化学催化特性及纳米金对蛋白质的强吸附能力及强的电子传导特性制备了无电子媒介体的过氧化氢生物传感器. 采用循环伏安法, 在无电子媒介体时, 该传感器对H₂O₂ 仍能具有良好的催化活性, 放大了电信号, 提高了该酶传感器的灵敏度及稳定性. 实验证明, 该传感器在H₂O₂浓度为 1.0×10^－6～ 1.0×10^－3 mol•L^－1范围内有线性响应, 线性相关系数r²＝0.9964. 并探讨了电极的稳定性、寿命及重现性.     

利培酮的电化学行为及应用研究

采用循环伏安法、线性扫描伏安法、常规脉冲伏安法和恒电位电解法等电化学手段, 详细研究了利培酮在pH 7.07～10.32 B-R缓冲溶液和0.2 mol•L^－1 NaOH溶液中的电化学行为. 研究表明: 在pH 7.07～10.07 B-R缓冲溶液中, 利培酮产生的P₁波为催化氢波. 在pH＝10.32 B-R缓冲溶液中, 利培酮可以产生P₂和P₃两个波. 其中, P₂波为不可逆的单电子还原波, P₃波可以分裂成两个波P_3a和P_3b. P_3a波为P₂波的进一步单电子还原, 而P_3b波则属于催化氢波. 在0.2 mol•L^－1 NaOH溶液中, 利培酮产生的P₄波是一个两电子的不可逆还原波. 另外, 根据P₁波的一阶导数峰电流与利培酮浓度在1.6×10^－5～2.0×10^－6 mol•L^－1 (r＝0.9950)间的线性关系, 建立了利培酮片剂中利培酮含量的测定新方法. 新方法的检出限为1.0×10^－6 mol•L^－1, 回收率在105%～102%之间, 相对标准偏差为0.84%.     

聚乙二醇接枝聚乳酸的自组装纳米微球的制备及性能

对制备的新型聚乙二醇(PEG)接枝聚乳酸(PLA)在水中的自组装性能进行研究, 探讨其作为纳米药物载体的可行性和稳定性. 目测法得到其溶解度为(2.16～4.32)×10^－2 mg•mL^－1; 荧光法得到聚合物的临界胶束浓度为1.12×10^－3 mg•mL^－1; 透射电子显微镜观察显示该聚合物在水中的自组装聚集体为纳米级球形; 动态激光光散射测试微球的粒径和Zeta电位发现, 在微球的制备过程中, 聚合物的亲/疏水性比例、水相介质及水溶液的pH值对它影响显著; 而制备后, 稀释和冷冻对它无显著影响, 改变微球的环境pH值至酸性, 出现聚集, 至碱性无影响. 研究结果显示, 该聚合物在水和磷酸钠盐缓冲液中可形成稳定的纳米微球, 通过微球的制备条件和存在环境可控制其粒径和Zeta电位, 因此根据应用需要, 通过控制其粒径和Zeta电位, 可能提高微球的在体血液循环时间并实现靶向缓释.     

基于N-十二酰基-l-脯氨酸为载体的对映异构PVC膜选择性电极的研制

合成了手性物质N-十二酰基-l-脯氨酸(N-DDO-l-Pro)(脯氨酸, Pro), 作为PVC膜电极的载体, 在PVC膜表面与被测试液中Cu(II)与脯氨酸形成的配合物[Cu(II)(l-Pro)₂]或[Cu(II)(d-Pro)₂]进行配体交换, 形成[(l-Pro)Cu(II) (N-DDO-l-Pro)]或[(d-Pro)Cu(II)(N-DDO-l-Pro)]配合物. 由于生成的配合物热力学稳定性不同, 电极能优先响应l-Pro, 线性范围10^－4～10^―1 mol•L^－1, 斜率57 mV•dec^－1, 检测限3.89×10^－5 mol•L^－1. 电极能够对脯氨酸进行手性检测, 其对映选择性系数lg为－3.19.     

Rapid detection of organophosphorus pesticide residue on Prussian blue modified dual-channel screen-printed electrodes combing with portable potentiostat

A new method consisted of a dual-channel screen-printed electrode (DSPE) efficient modified with Prussian blue and acetylcholinesterase was developed for the rapid detection of organophosphorus pesticide residues.     

Comparative Study of Pesticides Analysis Using Enzyme Inhibition Sensor and Gas Chromatography Methods

Pesticides are widely used in paddy field to control pests, diseases, weeds and other rice pathogens in minimizing a serious loss in rice production. The presence of pesticide residues and metabolites in rice, water, soil, currently represents a major environmental pollutant issues. It sometime will cause insect pest outbreaks in paddy field. An electrochemical enzyme inhibition sensor using screen-printed carbon working electrode with onboard carbon counter and silver–silver chloride pseudo-reference electrode for insecticides detection is described in this paper (Figure 1). The detection is based on the inhibition of insecticides used in paddy field towards acetyl-cholinesterase enzyme (AChE) with the presence of Acetylthiocholine Iodide (ATCh) substrate on the sensor surface. The mixtures of AChE enzyme (0.02 UmL^-1), electron mediator, TCNQ (1mM) and polypyrrole matrix (75 mM) were electro- polymerized on the sensor surface with a constant potential of 1.0V for 20 minutes. The sensor was soaked for 5 minutes with insecticides standard or sample containing insecticides before the electrochemical measurement was taken by adding Acetylthiocholine Iodide substrate in KCl (0.08M, pH 7.5) which acts as the enzyme mediator /substrate system. The current measurement was conducted using chronoamperometry at 100mV vs. on board screen-printed Ag-AgCl pseudo- reference electrode. Comparative analysis of spiked water samples with 0.1ppm pesticides and real samples (paddy) also were conducted using enzyme inhibition sensor and gas chromatography methods. From the data analysis, it showed very comparable results with R² = 0.96 in the correlation plot for paddy samples samples. This makes the developed sensor a potential tool for the rapid, simple and sensitive detection of insecticides residues in agriculture industry.     

Electrochemical Detection of Human Interleukin-15 using a Graphene Oxide-Modified Screen-Printed Carbon Electrode

Biofunctionalizing a simple and disposable graphene oxide-modified screen-printed carbon electrode with anti-interleukin-15 antibodies has been successfully demonstrated for the first time for the label-free electrochemical detection of interleukin-15, a biomarker of early HIV infection. To improve the electrochemical reactivity and introduce carboxylic groups on the surface of screen-printed carbon electrode, high-quality graphene oxide was used for the modification of screen-printed carbon electrode. With simple modification of the screen-printed carbon electrode, the device exhibited satisfactory sensitivity, selectivity, stability, reproducibility, and regenerability. The immunosensor provided a detection limit of 3.51?ng?mL^?1 and a sensitivity of 0.5655?µA cm^?2?mL?ng^?1. The simply constructed immunosensor thus rendered promising device for immunoreactions on the surface of the electrode.     

Determination of dinoseb by adsorptive stripping voltammetry using a mercury film electrode

An adsorptive stripping voltammetric method for the determination of the pesticide dinoseb (2-sec.-butyl-4,6-dinitrophenol) at the mercury film electrode is described. The deposition of the mercury film on a glassy carbon disk electrode was optimized. The temperature, at which the mercury film was deposited, was demonstrated to have a strong influence on the stripping peaks, the first one being much more intense than the second. A systematic study of the variables affecting the stripping response was carried out by differential pulse voltammetry. The results obtained have been compared with those at the HMDE; a significant improvement in the sensitivity of the method developed with the MFE was observed. Using a 300 s accumulation time, the limits of determination and detection were 3.6 × 10^–10 and 1.1 × 10^–10 mol L^–1, respectively. The effect of the presence of several herbicides on the dinoseb response was also tested. The method has been applied to the determination of the pesticide in spiked apple juice at two concentration levels: 12.0 and 1.2 g L^–1 of juice.     

Extraction and Detection of Pesticides by Cholinesterase Inhibition in a Two‐Phase System: a Strategy to Avoid Heavy Metal Interference

Abstract

A novel method of extraction has been developed to avoid the presence of heavy metals during the measurement of pesticides based on acetylcholinesterase (AchE) inhibition. Heavy metals have been in fact demonstrated in this article to interfere when the assay is performed by using the classic spectrophotometric Ellman's method. We present the results obtained with an assay system using two different phases, one organic and the other aqueous, in which the pesticide and the enzyme are, respectively, solubilized. In a first step, the concentration of the substrate acetylthiocholine (1 mM), of the enzyme (7 mU mL^?1), and the reaction time (20 min) for measurement of enzyme activity were optimized in aqueous solution. Next, the effect of an organic phase on the enzyme activity was studied by the addition of various solvents with the activity being evaluated after 10 min of mixing. It was found that by using hexane, the enzyme retained almost 100% of its activity, and this solvent was chosen for further development of the pesticide assay. Hexane was spiked with different concentrations of pesticides and then added to the enzyme aqueous phase. The pesticides were shown to be able to inhibit the enzyme by interaction at the interface between the two solutions. The degree of inhibition obtained with increasing amounts of pesticide was evaluated. A 50% inhibition was observed for a paraoxon solution of 9×10^?7 M.     

Book reviews

Inorganic mercury ions (Hg²⁺) in laboratory prepared solutions were determined with a screen-printed carbon electrode (SPCE) coated with a polyaniline-methylene blue (PANI-MB) polymer layer. The structure and properties of the PANI-MB polymer layer were compared to that of normal polyaniline (PANI) in order to elucidate the structure of the PANI-MB layer. The electrically-conducting polymers were prepared by electrochemical polymerisation of monomer solutions of aniline, and mixed solutions of aniline with methylene blue onto respective screen-printed carbon electrodes (SPCEs). Scanning Electron Microscopy (SEM) analyses of the SPCE polymer coated electrodes have shown that nanostructured materials have formed with the diameters of the PANI nanoclusters and PANI-MB nanorods at approximately 200 nm. Anodic stripping voltammetry (ASV) was used to evaluate a solution composed of 1 × 10^?6 M Hg²⁺, in the presence of the SPCE/PANI-MB polymer sensor electrode. The Hg²⁺ ions were determined as follows: (i) pre-concentration and reduction on the modified electrode surface and (ii) subsequent stripping from the electrode surface during the positive potential sweep. The experimental conditions optimised for Hg²⁺ determination included the supporting electrolyte concentration and the accumulation time. The results obtained have shown that the SPCE/PANI-MB polymer sensor electrode operates optimally at a pH 2, with the supporting electrolyte concentration at 0.5 M HCl. A linear calibration curve was found to be in the range of 1 × 10^?8 M to 1 × 10^?5 M Hg²⁺ after 120 s of pre-concentration. The detection limit was calculated and found to be 54.27 ± 3.28 µg L^?1 of Hg²⁺. The results have also shown that a conducting polymer modified SPCE sensor electrode can be used as an alternative transducer for the voltammetric stripping and analysis of inorganic Hg²⁺ ions.     

A screen-printed disposable biosensor for selective determination of putrescine

We have developed screen-printed carbon electrodes for the determination of putrescine (Put) via the enzyme monoamine oxidase that was immobilized on the surface of the electrode by cross-linking it with bovine serum albumin using glutaraldehyde. A mixture of 5 % of tetrathiofulvalene (TTF) and carbon ink was used for the fabrication of the screen-printed working electrode. Put was amperometrically detected by measurement of the current due to the oxidation of the mediator TTF. The use of TTF lowers the working potential to +250 mV (vs. a screen-printed Ag/AgCl reference electrode). Response is linear in the range from 16 to 101 μM, and the detection limit is 17.2?±?4.6 μM, with a reproducibility of 9.6 % (n?=?4) in terms of relative standard deviation. The effects of potentially interfering biogenic amines such as cadaverine, histamine, spermine, spermidine and tryptamine were also evaluated. The biosensor was successfully applied to the determination of Put in zucchini and anchovies.

Potentiometric determination of antihistaminic diphenhydramine hydrochloride in pharmaceutical preparations and biological fluids using screen-printed electrode

The performance characteristic of sensitive screen-printed (SPE) and carbon paste (CPE) electrodes was investigated for the determination of diphenhydramine hydrochloride (DPH) drug in pure, pharmaceutical preparations and biological fluids. Different experimental conditions namely types of materials used to prepare the working electrode (plasticizer), titrant, pH, temperature and life time were studied. Under these conditions, the SPE shows the best performance than CPE with respect to total potential change and potential break at the end point. The SPE and CPE exhibit suitable response to DPH in a concentration range of 1.0.10^{− 2} to 1.0.10^{− 6} mol/L with a limit of detection 9.70.10^{− 7} and 9.80.10^{− 7} mol/L, respectively. The slope of the system was 55.2 ± 1.0 and 54.7 ± 1.0 mV/decade over pH range 3.0–8.0 and 3–7 for SPE and CPE, respectively. Selectivity coefficients for DPH relative to a numbers of potential interfering substances were investigated. The SPE and CPE show a fast response time of 10 and 16 s and were used over a period of 2 months with a good reproducibility. The sensors were applied successfully to determine DPH in pharmaceutical preparations and biological fluids. The results are compared with the official method.     

An Electrochemical Biosensor for the Determination of Lactic Acid in Expiration

We have successfully developed an electrochemical biosensor which could detect low level concentration of misty lactic-acid (LA) directly. In our method, enzyme lactate oxidase (LOD) was immobilized within mesoporous silica (FSM8.0) which was formed on screen-printed Prussian Blue (PB)-modified working electrode and the top of that was covered with hydrophilic porous membrane. The resulting biosensor showed an excellent sensitivity (150nM-1.1 mM in solution) and can detect misty LA directly. This result indicates that our method provides a high-performance biosensor to determine LA levels in exhaled breath and that our approach is ideal for various medical applications and might improve the detection or management of disease.     

Preparation and application of a new glucose sensor based on iodide ion selective electrode

An electrode for glucose has been prepared by using an iodide selective electrode with the glucose oxidase enzyme. The iodide selective electrode used was prepared from 10% TDMAI and PVC according our previous study. The enzyme was immobilized on the iodide electrode by holding it at pH 7 phosphate buffer for 10 min at room temperature. The H₂O₂ formed from the reaction of glucose was determined from the decrease of iodide concentration that was present in the reaction cell. The iodide concentration was followed from the change of potential of iodide selective electrode. The potential change was linear in the 4×10⁻⁴ to 4×10⁻³ M glucose concentration (75-650 mg glucose/100ml blood) range. The slope of the linear portion was about 79 mV per decade change in glucose concentration. Glucose contents of some blood samples were determined with the new electrode and consistency was obtained with a colorimetric method. The effects of pH, iodide concentration, the amount of enzyme immobilized and the operating temperature were studied. No interference of ascorbic acid, uric acid, iron(III) and Cu(II) was observed. Since the iodide electrode used was not an AgI-Ag₂S electrode, there was no interference of common ions such as chloride present in biological fluids. The slope of the electrode did not change for about 65 days when used 3 times a day.