Effective enhancement of peroxydisulfate electrochemiluminescence on C-60/DDAB films

Effective enhancement of electrochermluminescence (ECL) of peroxydisulfate on a C-60/didodecyldimethyl ammonium bromide (C-60/DDAB) film coated glassy carbon electrode (GCE) surface is reported in this paper. The C60/DDAB film gave lower cathodic current in the presence of peroxydisulfate than that from a bare GCE. To our surprise, electrochemiluminescent intensity from peroxydisulfate reduction was effectively enhanced on the C60/DDAB film, which was 50 times and 250 times higher than those from a DDAB film coated and bare GCE, respectively. Moreover, the ECL onset potential on the C60/DDAB film was about -0.9 V, which positively shifted 200 mV compared with that from the bare GCE. Dissolved oxygen and the applied potential also affected the electrochemiluminescent intensity. The presence of oxygen decreased the intensity, and the intensity reached maximum at the applied potential of -1.7 V. The unique property will greatly enrich ECL studies and applications based on fullerenes.

Kinetic asymmetry in the gel-liquid crystalline state transitions of DDAB vesicles studied by differential scanning calorimetry

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

模拟生物膜的电化学研究

本文简要评述了生物膜领域的发展过程及研究现状，介绍了关于生物膜的一些基本性质和理论。采用电化学、光谱学以及扫描探针显微镜等方法对支撑双层磷脂膜、磷脂浇铸膜和泡囊等不同的模拟生物膜体系进行了研究。主要结果如下：1．将磷脂与芦丁的混合物滴于玻碳电极表面制备出了嵌有芦丁的磷脂浇铸膜，并以此膜为模拟生物膜的模型研究芦丁在磷脂膜内的电化学行为，以及芦丁对还原型辅酶烟酞胺腺漂吟二核昔酸（NADH）的催化氧化。芦丁与磷脂膜牢固地结合，在pH 7.4的磷酸缓冲溶液中，嵌在磷脂膜内的芦丁显示了准可逆电化学行为，也显示出很好催化氧化NADH的能力，使氧化电流明显增大。同时，与5*10~(-3)mol／L的NADH在裸玻碳电极上的电化学行为相比，其氧化过电位降低了约220 mV。2．在玻碳电极表面制备了嵌有芦丁的磷脂浇铸膜，嵌在磷脂膜内的芦丁显示了准可逆电化学行为。利用这种浇铸膜作为模拟生物膜的模型研究了芦丁对抗坏血酸的催化氧化，磷脂膜一方面与芦丁牢固结合，另一方面为芦丁催化抗坏血酸的氧化提供了理想的生物环境，在pH 7.4的磷酸缓冲溶液中，芦丁能有效地催化氧化抗坏血酸，使抗坏血酸的氧化过电位与裸玻碳电极上的电化学行为相比降低了约100 mV。该修饰磷脂膜和芦丁的玻碳电极对抗坏血酸的测定线性范围为2*10~(-4) mol／L-1.4*10~(-3) mol／L。3．将含有四硫富瓦烯（TTF）和黄嘿吟氧化酶的二甲基二（十二烷基）澳化钱（D DAB）泡囊滴于热解石墨电极表面，制备出一种基于磷脂浇铸膜的黄嘿吟生物传感器。TTF由于其可以有效地转移电子而被选作为电子媒介体，用安培检测的方法研究了工作电位、pH值对黄嘿吟传感器的影响。该传感器的响应时间小于10秒，其检测黄嘿吟线性范围从4*10~(-7)mol／L到2.4*l0~(-6)mol／L，最低检测限为3.2*10~(-7) mol/L。4；将辣根过氧化物酶（HRP）固定在修饰于玻碳电极表面的DDAB浇铸膜内，获得了IIR卫的直接电化学，并以此开发出一种不需媒介体的还02传感器，该传感器对H_2O_2的响应时间约5s，其检测姚。2线性范围从l*10~(-3) mol／L到4*10~(-3)mol／L，同时该传感器也显示出良好的重现性及稳定性。5，利用循环伏安的方法研究了HRP分子在双肉豆范磷脂酰胆碱（DMPC）磷脂膜内的电化学行为，并获得了一对氧化还原峰，说明了DMPC磷脂膜促进了HRP分子的电子传递，同时HRP分子仍保持对H_2O_2的催化生物活J险。UV一vis和CD的检测结果说明HRP分子在与磷脂膜相互作用后，其二级结构没有改变，而三级结构变得松散，这种三级结构的松散可能是使HRP分子的活性基团有所暴露，使得电子传递更容易。AFM实验同样也显示了HRP分子与DMPC磷脂膜间的强烈作用。

纳米结构界面组装及电化学SPR研究

围绕论文题目“纳米结构界面组装及电化学SPR研究”，我们将SPR与电化学技术有机的结合起来，建立了电化学SPR（EC-SPR）技术，开展了相关的EC-SPR研究工作。同时，在一些特殊纳米结构的界面组装方面进行了创新研究。本论文研究工作的主要内容和创新点表现在以下几个方面：1．首次成功地将纳米粒子自组装膜模板与化学镀金技术相结合成功地用于湿化学法制备SPR响应基片，攻克国际上仅用物理法制备SPR镀金片的局限和困难，为SPR技术的进一步普及奠定了一定的基础。2．此外，还成功地将纳米粒子自组装膜模板与化学镀金技术相结合，制备了Au（III）单晶纳米岛阵列薄膜及电极。3．在国内率先将电化学和表面等离子体共振（SPR）光谱技术相结合，构建了EC-SPR仪器操作系统；并将此技术用于现场原位表征和研究导电聚合物薄膜和生物大分子（DNA和电活性蛋白质分子）纳米结构组装体的光电特性。4. 首次合成并报道了纳米粒子模板法制备中空的银／金表面钉状双金属纳米粒子，及其在水和空气界面受扩散受限聚集控制的二维介观分形聚集。丰富和拓展了纳米粒子二维分形聚集的研究。5．将欠电位沉积电化学方法拓展用于表面微加工。实验结果表明，对化学镀制备的多晶金SPR响应基片进行连续的银欠电位沉积与溶出电化学处理，不仅可以改善金膜表面的粗糙度，还能对表面的原子进行结构重排，使其具有An（III）的电化学响应特征；SPR信号对SPR响应金膜表面的原子排列非常灵敏。6．将欠电位沉积电化学法用于新颖的纳米催化剂设计，首次制备了铂原子单层沉积的纳米金单层膜并成功地用于4电子氧催化还原反应。大基于纳米受限环境下水的特殊性质（不挥发性）的启示，成功地进行了DDAB表面活性剂泡囊和环状多金属氧酸盐（POM）纳米簇的仿生超分子模板界面静电组装。

模拟生物膜的电化学研究

本文简要介绍了生物膜的组成、结构和一些基本性质，详细描述了各种生物膜模型（支撑磷脂双层膜、非支撑磷脂双层膜、泡囊等等）的制备方法。概要地总结了模拟生物膜的各个领域的研究情况，着重评述了模拟生物膜在电化学、生物传感器、膜片钳、图案化领域的研究进展。采用电化学、各种谱学以及扫描探针显微镜等方法对支撑双层磷脂膜、磷脂浇铸膜等不同的模拟生物膜体系进行了研究。主要结果如下：1．将一种支撑磷脂膜一杂化双层膜（Hbrid bilayerer membrane，HBM）首次用于钙离子与磷脂作用的研究，以Fe（CN）63-为探针，发现钙离子可诱导HBM产生离子通道，且通道的打开与关闭能反复运转，并用STM观察这一现象。2.Ru（bPy）32+的电化学发光法和电催化法被首先用于研究支持脂质双层膜（sBLM）的离子通道行为。高氯酸根可以诱导DODAB（dimethyldioctadecylammonium）产生离子通道行为。离子通道的产生存在着一个闺值，当高氯酸根阴离子的浓度超过0.1μM时离子通道打开，当浓度低于0.1μM时离子通道关闭。当高氯酸根离子浓度高于0.1μM时，被打开的离子通道的数量随着高氯酸根阴离子浓度的增加而增加，在1200μM时达到平衡。离子通道的打开和关闭行为是可逆的。在此基础上，研制了一种用于检测高氯酸根离子的传感器。3，用循环伏安法和交流阻抗法研究了稀土离子与支撑磷脂双层膜的相互作用．稀土离子可以影响支撑磷脂双层膜的结构，使之产生一些小孔，通过这些小孔Fe（CN）63/4可以到达电极表面，显示其电化学行为。Fe（CN）63／4-的氧化还原电流随着稀土离子的浓度的增加而变大，对于E矿＋当浓度达到1．2卿时，电流不再增加。发现三种稀土离子与膜作用的能力如下：Eu3+＞Th3＋＞La3＋。4．铁氰酸根离子通常被用来作离子通道传感器的标记物。在本项工作中，我们首次发现铁氰酸根离子本身也可以作为一种刺激物来控制玻碳电极上DDAB（一种合成磷脂）制备出的支撑双层磷脂膜的通透性。我们利用循环伏安、交流阻抗的方法来研究这种现象。支撑双层磷脂膜与铁氰化物的反应与时间有关。进一步地，我们研制了一种铁氰酸根离子传感器。这种离子通道响应灵敏度较高，它可以检测的铁氰化物的最小浓度为5μM。5．稳定的磷脂浇铸膜是通过把含磷脂的氯仿溶液浇铸到玻碳电极上制备的。我们把一种新的媒介质一去甲肾上腺素嵌入到这种磷脂浇铸膜中。磷脂浇铸膜可以被视为一种生物膜模型。用这个体系对抗坏血酸进行电催化氧化，与在裸玻碳电极上相比，阳极过电位降低了约250 mV。浇铸膜内去甲肾上腺素的电化学行为是受扩散控制的，其扩散系数是1.87×10-5cm2／s。在浓度为0.5-10 mmol／L的范围内，催化电流随抗坏血酸的浓度增大而呈线性增加。在同时含有抗坏血酸和尿酸的溶液中，我们用循环伏安法可以同时侧得两个峰，这两个峰之间的峰位差大约为147mV。6．卵磷脂泡囊和血红蛋白在热解石墨电极上制备的薄膜内，血红蛋白可以实现其直接电化学。血红蛋白在薄膜内表现出薄层电化学行为。其式电位E0在pH 3.5-7.0内随pH值直线变化，斜率为-46.4 mV/pH。磷脂膜内的血红蛋白对H2O2显示了很好的催化还原行为。基于此，研制了无媒介体的H2O2传感器。7．我们合成了一种人工磷脂（二甲基二（十二烷基）澳化钱，DDAB）保护的金纳米粒子。在这些金纳米粒子的促进下，血红蛋白可以表现出直接电子转移（DET）反应，其式电位位于-169mVvs Ag/AgCl参比电极。光谱数据表明电极上的血红蛋白没有变性。这种磷脂保护的金纳米粒子很稳定（至少8个月），它们的平均直径是6.42nm。这是首次应用单层膜保护的纳米粒子去实现蛋白质的直接电化学反应。8．我们在一种新的基底一碳电极上构建了杂化双层膜（HBM）。这是对其它基底上构建的HBM的一种扩展。首先，通过电化学扫描将烷基胺修饰在碳电极表面，使之在电极上形成单层膜。由于烷基链部分向外，因此所构筑的界面是疏水的。然后在碳电极的疏水表面铺展一层磷脂单层膜。所生成的HBM通过电化学和ATR-FTIR技术来表征。根据ATR-FTIR的结果，脂质的有序常数（S）为0.73。这种杂化膜具有磷脂／烷基硫醇HBM的优点。这种HBM在生物传感面具有潜在的应用。

Coating Didodecyldimethylammonium Bromide onto Au Nanoparticles Increases the Stability of Its Complex with DNA

The stability of the complex of cationic lipid with nucleic acid, especially when facing serum, is crucial for the efficiency of gene delivery. Here, we demonstrated that the stability of the complex of didodecyldimethylammonium bromide (DDAB, a cationic lipid) with DNA in the presence of serum dramatically increased after coating DDAB onto the surface of the gold nanoparticles. The stability of the complex was demonstrated with dye intercalation assay, and agarose gel electrophoresis.

Surface modification of poly(dimethylsiloxane) microchips using a double-chained cationic surfactant for efficiently resolving fluorescent dye adsorption

This paper described a double-chained cationic surfactant, didodecyldimethylammonium bromide (DDAB). for dynamic surface modification of poly(dimethylsiloxane) (PDMS) microchips to reduce the fluorescent dyes adsorption onto the microchannel. When DDAB with a high concentration was present as the dynamic modification reagent in the running and sample buffer, it not only reversed the direction of electroosmotic flow, but also efficiently suppressed fluorescent dyes pyronine Y (PY) or rhodamine 8 (RB) adsorption onto the chip surface. In addition, vesicles formed by DDAB in the buffer with higher surface charge density and electrophoretic mobility could provide wider migration window and potential for the separation of compounds with similar hydrophobicity. Factors affecting modification, such as pH and concentrations of the buffer, DDAB concentration in the buffer were investigated. Compared with commonly used single-chained cetyltrimethylammonium bromide, DDAB provided a better modification performance.

The effect of template phase on the structures of As-synthesized silica nanoparticles with fragile didodecyldimethylammonium bromide vesicles as templates

The effect of template phase on the structures of as-synthesized silica nanoparticles with fragile DDAB vesicles as templates is reported. It is found that the template phase plays a critical role in the growth process of silica: the unstable DDAB vesicles in liquid-crystalline phase often lead to the formation of mesostructured solid spheres, and the rather stable DDAB vesicles in gel phase lead to the formation of hollow spheres with less mesostructures.

Robust core-shell supramolecular assemblies based on cationic vesicles and ring-shaped {Mo-154} polyoxomolybdate nanoclusters: Template-directed synthesis and characterizations

Substantial progress has been made recently in extending the supramolecular assembly of biomimetic structures to vesicle-based sophisticated nanocomposites and mesostructures. We report herein the successful preparation of unilamellar surfactant vesicles coated with a monolayer of ring-shaped {Mo-154} polyoxometalate (POM) nanoclusters, (NH4)(28)[Mo-154 (NO)(14)O(448)Hi(4)(H2O)(70)].approximate to 350H(2)O, by coulomb attractions using preformed didodecyldimethylammonium bromide (DDAB) surfactant vesicles as templates. The resultant vesicle-templated supramolecular assemblies are robust (they do not disintegrate upon dehydration) both at room-temperature ambient and vacuum conditions, as characterized by conventional transmission electron microscopy (TEM) and atomic force microscopy (AFM). The flexibility of the complex soft assemblies was also revealed by AFM measurements. The effect of POM-vesicle coulomb attractions on the dimensions of the templating vesicles was also investigated by using dynamic light scattering (DLS).Although origins of the structure stability of the as-prepared supramolecular assemblies are not clear yet, the nanometer scale cavities and the related properties of macroions of the POM clusters may play an important role in it.

Didodecyldimethylammonium bromide lipid bilayer-protected gold nanoparticles: Synthesis, characterization, and self-assembly

Didodecyldimethylammonium bromide (DDAB) lipid bilayer-protected gold nanoparticles (AuNPs), which were stable and hydrophilic, were synthesized by in situ reduction of HAuCl4 with NaBH4 in an aqueous medium in the presence of DDAB. As-prepared nanoparticles were characterized by UV-vis spectra, transmission electron microscopy, dynamic light scattering analysis, and X-ray photoelectron spectroscopy. All these data supported the formation of AuNPs. Fourier transform infrared spectroscopy (FTIR) and differential thermal analysis/thermogravimetric analysis data revealed that DDAB existed in a bilayer structure formed on the particle surface, resulting in a positively charged particle surface. The FTIR spectra also indicated that the DDAB bilayer coated on the surface of AuNPs was probably in the ordered gel phase with some end-gauche defects. On the basis of electrostatic interactions between such AuNPs and anionic polyelectrolyte poly(sodium 4-styrenesulfonate) (PSS), we successfully fabricated (PSS/AuNP)(n) multilayers on a cationic polyelectrolyte poly(ethylenimine) coated indium tin oxide substrate via the layer-by-layer self-assembly technique and characterized as-formed multilayers with UV-vis spectra and atomic force microscopy.

Investigation of the influence on conformational transition of DNA induced by cationic lipid vesicles

Recent studies have focused on the structural features of DNA-lipid assemblies. In this paper we take nile blue A (NBA) as a probe molecule to study the influence of the conformational transition of DNA induced by didodecyldimethylammonium bromide (DDAB) cationic vesicles to the interaction between DNA and the probe molecules. We find that upon binding to DNA, a secondary conformational transition of DNA induced by the cationic liposome from the native B-form to the C-form resulted in the change of binding modes of NBA to DNA and different complexes are formed between DNA, DDAB and NBA.

Lipid membrane immobilized horseradish peroxidase biosensor for amperometric determination of hydrogen peroxide

Stable films of didodecyldimethylammonium bromide (DDAB, a synthetic lipid) and horseradish peroxidase (HRP) were made by casting the mixture of the aqueous vesicle of DDAB and HRP onto the glassy carbon (GC) electrode. The direct electron transfer between electrode and HRP immobilized in lipid film has been demonstrated. The lipid films were used to supply a biological environment resembling biomembrane on the surface of the electrode. A pair of redox peaks attributed to the direct redox reaction of HRP were observed in the phosphate buffer solution (pH 5.5). The cathodic peak current increased dramatically while anodic peak decreased by addition of small amount H2O2. The pH effect on amperometric response to H2O2 was studied. The biosensor also exhibited fast response (5 s), good stability and reproducibility.

Hydrogen peroxide biosensor based on microperoxidase-11 entrapped in lipid membrane

A highly catalytic activity microperoxidase-11 (MP-11) biosensor for H2O2 was developed to immobilizing the heme peptide in didodecyldimethylammonium bromide (DDAB) lipid membrane. The enzyme electrode thus obtained responded to H2O2 without electron mediator or promoter, at a potential of +0.10 V versus Ag \ AgCl. A linear calibration curve is obtained over the range from 2.0 x 10(-5) to 2.4 x 10(-3) M. The biosensor responds to hydrogen peroxide in 15 s and has a detection limit of 8 x 10(-7) M (S/N = 3) Providing a natural environment with lipid membrane for protein immobilization and maintenance of protein functions is a suitable option for the design of biosensors.

Liposome-mediated conformation transition of DNA detected by molecular probe: methyl green

Recent studies have focused on the structural features of DNA-lipid assemblies. In this paper, we take methyl green (MG) as a probe molecule to detect the conformational change of DNA molecule induced by dimethyldioctadecylammonium bromide (DDAB) liposomes before the condensation process of DNA begins. DDAB-induced DNA topology changes were investigated by cyclic voltammetry (CV), circular dichroism (CD) and UV-VIS spectrometry. We find that upon binding to DNA, positively charged liposomes induce a conformational transition of DNA molecules from the native B-form to the C motif. Conformational transition in DNA results in the binding modes of MG to DNA, changing and being isolated from DNA to the solution. More stable complexes are formed between DNA and DDAB. That is also proved by the melting study of DNA.