Direct Electron Transfer of Horseradish Peroxidase in Gellan Gum–Hydrophilic Ionic Liquid Gel Film

A new composite film of microbial exocellular polysaccharide‐gellan gum (GG) and hydrophilic room temperature ionic liquid 1‐butyl‐3‐methyl‐imidazolium tetrafluoroborate (BMIMBF₄) was firstly used as an immobilization matrix to entrap horseradish peroxidase (HRP), and its properties were studied by UV/vis spectroscopy, cyclic voltammetry and electrochemical impedance spectroscopy. The results showed that BMIMBF₄ could promote the electron transfer between HRP and electrode surface, and the existence of GG could successfully immobilize BMIMBF₄ on the electrode surface with improved stability. HRP–BMIMBF₄–GG/GCE exhibited a pair of well‐defined and quasireversible cyclic voltammetric peaks in 0.1 M pH 7.0 phosphate buffer solutions at 1.8 V/s, which was the characteristic of HRP Fe(III)/Fe(II) redox couples. The formal potentials (E°′) was ?0.368 V (vs. SCE) and the peak‐to‐peak potential separation (ΔE_P) was 0.058 V. The peak currents were five times as large as those of HRP–GG/GCE. The average surface coverage (Γ*) and the apparent Michaelis‐Menten constant (K_m) were 4.5×10^?9 mol/cm² and 0.67 μM, respectively. The electron transfer rate constant was estimated to be 15.8 s^?1. The proposed electrode showed excellent electrocatalytic activity towards hydrogen peroxide (H₂O₂). The linear dynamic range for the detection of H₂O₂ was 0.05–0.5 μM with a correlation coefficient of 0.9945 and the detection limit was estimated at about 0.02 μM (S/N=3). BMIMBF₄–GG composite film was promising to immobilize other redox enzymes or proteins and attain their direct electrochemistry.     

Direct Electrochemistry and Electrocatalysis Behaviors of Glucose Oxidase Based on Hyaluronic Acid-Carbon Nanotubes-Ionic Liquid Composite Film

Multi‐walled carbon nanotubes (MWNTs) were dispersed in the ionic liquid [BMIM][BF₄] to form a uniform black suspension. Based on it, a novel glucose oxidase (GOx)‐hyaluronic (HA)‐[BMIM][BF₄]‐MWNTs/GCE modified electrode was fabricated. UV‐vis spectroscopy confirmed that GOx immobilized in the composite film retained its native structure. The experimental results of EIS indicated MWNTs, [BMIM][BF₄] and HA were successfully immobilized on the surface of GCE and [BMIM][BF₄]‐MWNTs could obviously improve the diffusion of ferricyanide toward the electrode surface. The experimental results of CV showed that a pair of well‐defined and quasi‐reversible peaks of GOx at the modified electrode was exhibited, and the redox reaction of GOx at the modified electrode was surface‐confined and quasi‐reversible electrochemical process. The average surface coverage of GOx and the apparent Michaelis‐Menten constant were 8.5×10⁻⁹ mol/cm² and 9.8 mmol/L, respectively. The cathodic peak current of GOx and the glucose concentration showed linear relationship in the range from 0.1 to 2.0 mmol/L with a detection limit of 0.03 mmol/L (S/N=3). As a result, the method presented here could be easily extended to immobilize and obtain the direct electrochemistry of other redox enzymes or proteins.     

Three novel high performance affinity chromatographic media for the separation of antithrombin III from human plasma.

Novel monodisperse, non-porous, cross-linked poly (glycidyl methacrylate) beads (PGMA) were employed as the support for high performance affinity chromatography. Heparin was covalently attached to PGMA beads by three different coupling methods. Heparin-PGMA-I was prepared by directly coupling amino-groups of heparin with PGMA. Heparin-PGMA-II and III were prepared by the coupling of heparin to amino-PGMA, which was obtained by amination of PGMA. Heparin-PGMA-II was prepared by coupling the carboxyl groups of heparin to amino-PGMA by using water-soluble carbodiimide as coupling reagent, and heparin-PGMA-III was prepared by the reductive amination of heparin and amino-PGMA with sodium cyanoborohydride. The heparin contents of heparin-PGMA-I, II and III were 1.6, 10.2 and 1.0 mg/g beads, respectively. Their affinity capacities for antithrombin III were investigated. Their binding activity to antithrombin III was not proportional to the content of heparin immobilized, and heparin-PGMA-I was the most efficient affinity medium for antithrombin III. The resultant affinity media presented minimal non-specific interaction with other proteins and can be used in a wide pH range. All the three heparin-PGMA beads were exploited for the separation of antithrombin III from human plasma. The purity of antithrombin III obtained was higher than 90%, which was confirmed by high performance size exclusion chromatography.     

Direct electrochemistry of glucose oxidase based on its direct immobilization on carbon ionic liquid electrode and glucose sensing

Direct electrochemistry of glucose oxidase (GOx) has been achieved by its direct immobilization on carbon ionic liquid electrode (CILE) with a conductive hydrophobic ionic liquid, 1-butyl pyridinium hexafluophosphate ([BuPy][PF₆]) as binder for the first time. A pair of reversible peaks is exhibited on GOx/CILE by cyclic voltammetry. The peak-to-peak potential separation (ΔE_P) of immobilized GOx is 0.056 V in 0.067 M phosphate buffer solution (pH 6.98) with scan rate of 0.1 V/s. The average surface coverage and the apparent Michaelis–Menten constant are 6.69 × 10⁻¹¹ mol·cm⁻² and 2.47 μM. GOx/CILE shows excellent electrocatalytic activity towards glucose determination in the range of 0.1–800 μM with detection limit of 0.03 μM (S/N = 3). The biosensor has been successfully applied to the determination of glucose in human plasma with the average recoveries between 95.0% and 102.5% for three times determination. The direct electrochemistry of GOx on CILE is achieved without the help of any supporting film or any electron mediator. GOx/CILE is inexpensive, stable, repeatable and easy to be fabricated.     

Ex vivo identification of circulating tumor cells in peripheral blood by fluorometric “turn on” aptamer nanoparticles

The detection of the circulating tumor cells (CTCs) detached from solid tumors has emerged as a burgeoning topic for cancer diagnosis and treatment. The conventional CTC enrichment and identification mainly rely on the specific binding of the antibodies on the capture interface of the magnetic nanoparticles with the corresponding biomarkers on the cell membranes. However, these methods could easily generate false-negative results due to the extremely low concentration of CTCs and the internal heterogeneity of the tumor cells. Herein, with the aim of selectively identifying CTCs and improving the detection accuracy in peripheral blood, we designed the fluorometric “turn on” Au nanoparticles (DHANs) with the modification of a tumor-targeted moiety, dehydroascorbic acid (DHA) and a fluorometric aptamer, which could be “switched-on” by an over-expressed intracellular protein, namely hypoxia-inducible factor-1α (HIF 1α). This novel nanoformulated detection platform demonstrated the great capacity for visualizing various CTCs in peripheral blood with significantly improved detection efficiency and sensitivity. As a result, the nanoplatform has a great potential to be further applied for CTC detection in vitro or in vivo, which holds promise for extensive CTC studies.

The detection of the circulating tumor cells (CTCs) detached from solid tumors has emerged as a burgeoning topic for cancer diagnosis and treatment.     

改进遗传算法用于未知组分数的重叠色谱峰的解析

按照指数修正的Gauss卷积色谱峰模型，构造了结合模拟退火及变长染色体的改进遗传算法，并结合爬山法，可以方便快捷地进行数目未知的重叠色谱峰的精确解析；此法成功地应用于大鼠脑微透析液氨基酸定量分析中，解析结果良好。     

铈钼氧化物表面氧性质和催化性能

在甲苯选择性氧化制苯甲醛反应中,Mo基氧化物是一类重要的催化剂[1]．通常的认识是反应物与催化剂表面晶格氧作用,并通过催化剂本身的还原和氧化的循环过程促使反应进行。生成产物．因此,催化剂表面不同氧物种的热脱附性能应与催化反应性能密切相关．对于Ce-Mo氧化物的TPD-MS研究,尚未见文献报导．为了能获得该方面的信息,本文应用程序升温脱附-质谱检测（TP-MS）联用技术,对Ce-Mo氧化物样品进行了表面氧TPD谱测定和动力学参量等计算,并试图与其催化性能进行关联．1实验部分1．1样品的制备和表征分别将一定质量的硝酸铈铵和仲…     

Reaction mechanism of simultaneous catalytic removal of NOx and diesel soot particulates

Reactions of diesel soot and NOx with and without O₂ were carried out over CuFe₂O₄ catalyst. The ignition temperature of soot with the NO+O₂ feed was lower than that in O₂ or NO but close to those in NO₂ and NO₂+O₂, indicating the implication of NO₂ especially in decreasing the ignition temperature. On the other hand, the reduction of NOx into N₂ was enhanced by coexisting O₂. Based on these results and mechanisms of O₂-soot and NO-soot reactions, the possible reaction mechanism of the simultaneous NOx-soot removal with the NO+O₂ feed has been proposed.     

MoO3-x/PCN的原位合成及其增强光催化产氢性能的研究

本文通过简单的一步浸渍煅烧法原位合成了氧化钼纳米晶/聚合物氮化碳复合光催化剂,该不含铂基助催化剂的氧化钼修饰聚合物氮化碳光催化剂在可见光照射下表现出增强的光催化产氢性能,最高产氢速率为15.6 μmol/h,是普通聚合物氮化碳样品的3倍以上. 相应的结构与性能的分析表明,与后浸渍法不同,在原位生长过程中高分散的超小氧化钼纳米晶体与聚合物氮化碳之间形成了紧密的耦合界面结构,可见光产氢活性的提升源自高分散的超小氧化钼纳米晶与聚合物氮化碳之间形成的紧密界面,以及该界面结构形成的肖特基结带来的有效电荷载流子转移.     

基于掺Zn氮化碳和BiVO4构建Z型光催化系统实现完全分解水

随着现代工业的迅猛发展和化石燃料的过量使用, 全球范围内能源和环境问题日益严峻, 因此利用丰富的太阳光能分解水来直接制取清洁的氢气具有诱人的应用前景. 目前, 聚合物半导体石墨相氮化碳(g-C3N4)因其廉价、稳定、不含金属组分和独特的电子能带结构已被广泛应用于光解水产氢研究. 然而, 氮化碳具有结晶度差、光生载流子易复合的缺点.众所周知, Z型体系可以很好地减少电子和空穴的复合问题. 同时, 催化剂只需分别满足光解水过程的一端, 这使得半导体光催化剂的选择非常丰富, 可以大大拓宽材料体系. 因此, 将g-C3N4运用到Z型体系中的研究得到了广泛关注. 然而, 这些研究多集中在如何增强g-C3N4的产氢能力方面, 对实现水的完全分解的研究鲜见报道.本实验设计了这样一种Z型体系: 使用掺Zn的g-C3N4作为产氢端, BiVO4作为产氧端, Fe3+/Fe2+作为氧化还原对. 实验结果表明, 该体系可以在全波段下实现水的完全分解(氢氧比为2:1), 并且保持相当高的稳定性.实验所使用的氮化碳为固相法烧结尿素制得, Zn的掺杂采用浸渍法, 同时通过水热法合成BiVO4, 使用Pt作为助催化剂. 通过搭建含有不同组成成分的Z型体系, 将它们的性能和表征结果进行比较分析.通过XRD, UV-Vis, SEM和XPS等测试手段对催化剂进行表征. XRD分析结果表明成功合成了掺杂Zn的石墨相氮化碳. UV-Vis则显示随着Zn浓度的提高, 吸收边发生变化. 通过改变掺杂Zn的浓度, 得到了能够实现完全分解水的Z型体系,其最佳掺杂比例为: ZnCl2和氮化碳的质量比为1:10. 为了排除单催化剂和Pt颗粒对完全分解水性能的影响, 分别作了单独产氢端、单独产氧端、预负载Pt和光沉积Pt的性能测试. 从SEM中没有发现g-C3N4和BiVO4的异质结结构. 这些结果表明所搭建的是典型的利用氧化还原离子对为中间电子传输载体的Z型体系, 经长达12 h的持续测试证明其具有较高的稳定性.为了研究Zn在构建Z型中所起的作用, 分别采用文献中报道的原位和浸渍法实现Zn的掺杂. 对这两种掺杂方式的性能测试表明, 只有采用浸渍法时, 所构建的Z型体系具有完全分解水的能力. 对这两种方法得到的掺Zn氮化碳进行表面化学组成和价态(XPS)的分析. 结果显示, 两种掺杂方法都可以通过形成Zn=N键的形式实现Zn的掺杂, 但浸渍法使Zn在g-C3N4表面分布更均匀, 同时对氮化碳原本三嗪环的破坏较小, 因此具有更好的还原能力, 可以与BiVO4匹配以构成Z型体系.实验通过采用掺杂Zn的氮化碳作为产氢催化剂, BiVO4作为产氧催化剂, Fe3+/Fe2+作为氧化还原中间体, 构建了典型的Z型体系. 该体系在Zn的掺杂浓度为10%时能够实现长时间稳定的完全分解水.