Elaboration and characterization of spatially controlled assemblies of complementary polyphenol oxidase-alkaline phosphatase activities on electrodes

The electrooxidation of a biotin pyrrole has allowed the formation of biotinylated polypyrrole films. Gravimetric measurements based on a quartz crystal microbalance demonstrate the efficient coupling of avidin, biotinylated polyphenol oxidase (PPO-B) and avidin-labeled alkaline phosphatase (AP-A) with the underlying biotinylated polymer film. The estimated mass increase corresponds to the anchoring of 1.6-1.8 equivalent layer of proteins. A step-by-step construction of bienzyme multilayers composed of PPO-B and AP-A was carried out on the electrode surface modified by the biotinylated polypyrrole film through avidin-biotin bridges. A spatially controlled distribution of the two enzymes was performed by the formation of one AP-A layer on 1, 5, and 10 PPO-B layers. The resulting bienzyme electrodes were applied to the determination of phenyl phosphate on the basis of amperometric detection of enzymically generated o-quinone at -0.2 V. Their analytical performances were analyzed in relation to the design of the enzyme architectures and in comparison with the amperometric behavior of the monoenzymatic electrodes (PPO-B electrode and AP-A electrode). It appears that at the 10-layer-PPO-B polypyrrole electrode only 4% of phenol is transformed, whereas 42-69% of phenyl phosphate is enzymatically consumed and detected at the AP-A polypyrrole electrode, depending on the enzyme activity. For the bienzymatic AP-A/PPO-B polypyrrole electrodes, the activity of each immobilized enzyme clearly affects the biosensor performance, the main limiting factor being the very low efficiency of PPO-B at pH 8.8.     

A simple strategy based on photobiotin irradiation for the photoelectrochemical immobilization of proteins on electrode surfaces

A photoactivable organic polymer was prepared first by electrogeneration of a conductive biotinylated polypyrrole film in acetonitrile electrolyte. The successive anchoring of avidin and photobiotin led to a multilayer configuration. The latter was illuminated with light (wavelength 370–400 nm) in the presence of proteins adsorbed onto its surface. The irradiation allowed the covalent linking of the proteins to the modified electrode. As a result of the photochemical reaction, a monolayer of enzyme (glucose oxidase, GOX or alkaline phosphatase, AP) was covalently bound to the photobiotin-modified surface with retention of their catalytic activities. The surfacic activities were 34 and 1.69 mU cm^− 2 for GOX and AP photobiotin electrodes, respectively. These enzyme electrodes were compared to similar configurations obtained through the immobilization of biotinylated glucose oxidase or avidin-conjugated alkaline phosphatase on biotinylated polypyrrole film. Our results suggest that both procedures led to the immobilization of the same enzyme amount, namely a protein monolayer. This novel photo-immobilization methodology was also successfully applied to the anchoring of an anti-cholera toxin antibody which was then detected by a secondary antibody labelled with a peroxidase.     

A disposable,reagentless, third-generation glucose biosensor based on overoxidized poly(pyrrole)/tetrathiafulvalene-tetracyanoquinodimethane composite

A disposable glucose biosensor based on glucose oxidase immobilized on tetrathiafulvalene-tetracyanoquinodimethane (ITF-TCNQ) conducting organic salt synthesized in situ onto an overoxidized poly(pyrrole) (PPy(ox).) film is described. The TIF-TCNQ crystals grow through the nonconducting polypyrrole film (ensuring electrical connection to the underlying Pt electrode) and emerge from the film forming a treelike structure. The PPy(ox) film prevents the interfering substances from reaching the electrode surface. The sensor behavior can be modeled by assuming a direct reoxidation of the enzyme at the surface of the TTF-TCNQ crystals. A heterogeneous rate constant around 10(-6) - 10(-7) cm s(-1) has been estimated. The biosensor is nearly oxygen- and interference-free and when integrated in a flow injection system displays a remarkable sensitivity (70 nA/mM) and stability.     

Electroenzymatic polypyrrole-intercalator sensor for the determination of West Nile virus cDNA

The chemical binding of a redox acridone derivative onto a polypyrrole film functionalized by N-hydroxysuccinimide groups provided an electrode capable of anchoring DNA duplex by simple insertion of the grafted acridone intercalator into the dsDNA solution. This electrode was applied for the detection of a ssDNA derived from a West Nile virus sequence. The latter was thus amperometrically detected after its hybridization in solution with a biotinylated complementary oligonucleotide followed by its anchoring and labeling by a glucose oxidase at 1 pg/mL.     

Electrodeposited biotinylated polypyrrole as an immobilization method for impedimetric immunosensors

The potentialities of an electrodeposited biotinylated polypyrrole film as an immobilization matrix for the fabrication of impedimetric immunosensors are described. Biotinylated antibody (anti-human IgG), used as a model system, was attached to free biotin groups on the electrogenerated polypyrrole film using avidin as a coupling reagent. The resulting recognition interface consisted of a highly oriented monolayer immobilized onto the polymer surface. Cyclic voltammetry was used to characterize the polymer film. Additionally, scanning electron microscopy and atomic force microscopy were used to investigate the morphology of the immobilized material. This immobilization method allows the obtention of a highly reproducible and stable device. The resulting immunosensor has a linear dynamic range of 10-80 ng.ml/sup -1/ of antigen and a detection limit of 10 pg.ml/sup -1/. Furthermore, this immunosensor exhibited minor loss in response after two regeneration steps.     

Low density lipoprotein sensor based on surface plasmon resonance

Biotinylated heparin has been immobilized onto self-assembled monolayer of 4-aminothiophenol using avidin–biotin specific binding. The modified electrodes have been characterized using surface plasmon resonance technique (SPR), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), atomic force microscopy (AFM) and contact angle (CA) measurements. The interaction of immobilized biotinylated heparin with low density lipoprotein (LDL) has been studied using surface plasmon resonance technique. The biotinylated heparin modified electrode can be used to detect LDL in the range of 20 to 100 mg/dl with the sensitivity of 513.3 m°/μM.     

Electrochemical biosensing based on polypyrrole/titania nanotube hybrid

The glucose oxidase (GOD) modified polypyrrole/titania nanotube enzyme electrode is fabricated for electrochemical biosensing application. The titania nanotube array is grown directly on a titanium substrate through an anodic oxidation process. A thin film of polypyrrole is coated onto titania nanotube array to form polypyrrole/titania nanotube hybrid through a normal pulse voltammetry process. GOD-polypyrrole/titania nanotube enzyme electrode is prepared by the covalent immobilization of GOD onto polypyrrole/titania nanotube hybrid via the cross-linker of glutaraldehyde. The morphology and microstructure of nanotube electrodes are characterized by field emission scanning electron microscopy and Fourier transform infrared analysis. The biosensing properties of this nanotube enzyme electrode have been investigated by means of cyclic voltammetry and chronoamperometry. The hydrophilic polypyrrole/titania nanotube hybrid provides highly accessible nanochannels for GOD encapsulation, presenting good enzymatic affinity. As-formed GOD-polypyrrole/titania nanotube enzyme electrode well conducts bioelectrocatalytic oxidation of glucose, exhibiting a good biosensing performance with a high sensitivity, low detection limit and wide linear detection range.     

Polypyrrole-based optical probe for a hydrogen peroxide assay

An optical sensing probe has been developed by taking advantage of the polypyrrole (PPy) chromophore. The absorbance of the oxidation product of pyrrole, i.e., solubilized PPy colloids, is shown to be directly proportional to the concentration of hydrogen peroxide, when H2O2 is used as an oxidant for pyrrole in the presence of a surfactant, sodium dodecyl sulfate, and Fe(II) in a slightly acidic aqueous solution. Based on this result, a new optical sensing method has been developed for the determination of H2O2. The probe has also been applied to optical sensing of ethanol by biocatalyzed generation of H2O2 in the presence of O2, ethanol, and alcohol oxidase. The novel methodology is expected to provide a general protocol for the determination of H2O2 as well as for numerous other oxidase-based reactions producing H2O2 as a product.     

TiO_2-聚吡咯复合材料的制备及光催化性能

采用原位氧化聚合法制备TiO2-聚吡咯复合材料,研究吡咯与TiO2配比对TiO2-聚吡咯复合材料在紫外光和太阳光下光催化降解甲基橙的影响,利用傅里叶红外光谱仪、X射线衍射仪、紫外-可见光谱仪对样品进行表征。结果表明,TiO2-聚吡咯复合材料与纯聚吡咯相比,聚吡咯本征态特征峰和C─N伸缩振动峰峰值都向高波数偏移,TiO2和聚吡咯的复合并不是单纯的物理复合,而是产生了化学作用力;通过改变吡咯的添加量,可以控制聚吡咯在TiO2粉体表面的包覆量,聚吡咯的包覆对TiO2的晶型没有影响;聚吡咯对TiO2的包覆可降低TiO2的禁带宽度至2.90 eV,使TiO2-聚吡咯复合材料可吸收的波长范围拓宽到可见光区,提高复合材料在可见光下的光催化能力;适量的聚吡咯包覆可以提高TiO2-聚吡咯复合材料的光催化活性,以紫外灯作为光源催化降解甲基橙,当吡咯包覆质量分数为0.06时,复合材料的电子-空穴对分离效果最好;以太阳光作为光源催化降解甲基橙,当吡咯包覆质量分数为0.04时,复合材料的光谱拓展效果最好。     

聚吡咯/聚酯纤维复合材料吸波性能的探讨

聚吡咯是含有π电子共扼体系的高聚物,经掺杂反应电导率发生变化,当其电导率处于半导体状态时,具有良好的吸波性能.本文采用原位聚合法以聚酯纤维为基布,以吡咯为单体,制备具有良好吸波性能的柔性聚吡咯/聚酯纤维复合材料.首先探讨了吡咯浓度,温度,时间对复合材料吸波性能和表面电阻的影响;其次研究了其外观形貌和强力.结果表明:制备的聚吡咯复合材料具有良好的吸波性能;在0~106Hz频率内,吡咯浓度0.8 mol/L实验组,介电常数的实部、虚部均最大;1.0 mol/L实验组的损耗角正切最大;吡咯浓度0.8 mol/L实验组表面电阻最小;室温实验组的介电常数实部、虚部、损耗角正切最大,且明显优于其他组.反应时间150 min实验组的各项介电性能都明显优于其他组,且其电阻最小,导电率最好.     

Surface modification of natural and synthetic hydroxyapatites powders by grafting polypyrrole

The modification of hydroxyapatite surface by grafting polypyrrole has been investigated with two hydroxyapatites (HA) powders. One is natural derived from bovine bone, it was prepared by calcination at 750 °C. The other is synthetic synthesized by the sol–gel method using Ca(NO₃)₂·4H₂O and P₂O₅. The presence of (C₄H₃N) _n polymeric fragment bound to HA surface was evidenced by infrared analysis. X-ray powder analysis has shown that the apatite structure remains unchanged during the surface modification. The thermogravimetric analysis has shown that the weight loss exhibited by HA increased from 8.7 to 47.8 and from 18.3 to 42.8 wt% for natural hydroxyapatite (NHA)/polypyrrole and synthetic hydroxyapatite (SHA)/polypyrrole, respectively, as the pyrrole solution concentration increased from 5 to 15 wt%. Grafting of polypyrrole on HA surface caused an increase in specific surface area up to 113 m²/g for SHA and up to 107 m²/g for NHA aged in 15 wt% pyrrole solution (HA/15Pyrrole). According to the results found for these two apatites, a mechanism of surface modification was proposed for the formation of N–H hydrogen bonds as the result of a reaction between the C₄H₅N organic reagent and OH^? ions of the HA.     

Enzyme electrodes with conductive polymer membranes and Langmuir-Blodgett films

A glucose sensor consisting of a conductive polypyrrole membrane and a lipid Langmuir-Blodgett (LB) film has been investigated. Different arrangements of the biosensor on the electrodes examined were (1) electrode with glucose oxidase (GOD)-immobilized lipid LB films; (2) GOD-immobilized LB film coated on polypyrrole-modified electrode; (3) electrode with a GOD-immobilized polypyrrole membrane; (4) GOD-immobilized LB film coated on a GOD-polypyrrole-modified electrode. It was shown that the quality of the biosensor was apparently improved in case (4) with respect to both the detectable concentration range of glucose and the lifetime over which it could be used. The number of layers of the LB film has a marked influence on the sensitivity of the biosensor, an optimum number of layers existing for the best response. The mechanism of such an improvement is discussed.     

An Amperometric Glucose Biosensor With Enhanced Measurement Stability and Sensitivity Using an Artificially Porous Conducting Polymer

A conducting polymer [polypyrrole (PPy)]-based amperometric biosensor fabricated on a platinum-coated nanoporous alumina electrode has been described. This fabricating process introduced artificial porosity into the PPy film, and the template pore sizes were carefully chosen to match the size of the glucose oxidase (GOx) molecule. The $hbox{PF}_{6}^{-}$-doped PPy film was synthesized with 0.05 M pyrrole and 0.1 M $hbox{NaPF}_{6}$ at a current density of 0.3 $hbox{mA/cm}^{2}$ for 90 s. Immobilization was done by physically adsorbing 5 $muhbox{L}$ of GOx on the nanoporous PPy film. Glutaraldehyde (0.1 wt.%, 5 $muhbox{L}$) was used for cross-linking. The synthesized films were characterized by using an electrochemical technique and scanning electron microscopy (SEM). Amperometric responses were measured as a function of different concentrations of glucose at 0.4 V. Nanoporous electrodes lead to high enzyme loading, whereas the use of a cross-linking agent increased stability, sensitivity, reproducibility, repeatability, and shelf life.      

吡咯浓度对聚吡咯涂层棉复合材料吸波性能的影响

随着手机、电脑、电视等广泛应用于生活和工作中,电磁辐射日益严重,而电磁辐射危害人体健康且影响精密电子设备的运行.为了解决上述问题,以棉机织物为基布,以吡咯为单体,采用原位聚合法制备具有良好吸波性能的柔性聚吡咯涂层棉复合材料,探讨了吡咯浓度对复合材料介电常数实部、虚部、损耗角正切、表面电阻的影响,并对其外观形貌进行了研究.研究表明:吡咯浓度对聚吡咯涂层棉复合材料介电常数实部、虚部、损耗角正切、表面电阻影响较大;吡咯浓度为0.6 mol/L时,聚吡咯涂层棉复合材料的介电常数实部和虚部均最大,吡咯浓度为0.4 mol/L时,聚吡咯涂层棉复合材料损耗角正切值最大.     

聚吡咯涂层织物的介电性能研究

采用原位聚合法以棉机织物、尼龙为基布,以吡咯为单体,制备了具有良好介电性能的柔性聚吡咯涂层棉织物和聚吡咯涂层尼龙织物,探讨了掺杂剂种类、掺杂剂浓度对聚吡咯涂层棉织物、聚吡咯涂层尼龙织物介电性能和表面电阻的影响.结果表明,掺杂剂对聚吡咯复合材料的介电性能和表面电阻的影响较大.所制备的聚吡咯涂层棉织物、聚吡咯涂层尼龙织物均具备良好的介电性能和导电性,为最终开发出较为实用的多功能吸波复合材料奠定了基础.     

V2O5/polypyrrole core-shell nanotubes for gas sensor

V2O5/polypyrrole core-shell nanotubes have been synthesized through an in situ polymerization of pyrrole monomers in the presence of prepared vanadium oxide nanotubes. Formation of polypyrrole in core-shell structure was endorsed by FTIR spectral analyses. Transmission electron microscopy images revealed that one dimensional morphology of vanadium oxide nanotubes remained undisturbed upon coating of polypyrrole, and polypyrrole was uniformly coated on the surface of vanadium oxide nanotubes, with a thickness of 30 nm. XRD suggested certain synergetic interaction existed in the core-shell structure, probably resulting in the enhanced thermal stability of polypyrrole coatings. The gas tests showed that the core-shell structure exhibited a high response, good stability and a short response/recovery time in the detection of different concentrations of ethanol at room temperature, implying its potential application for gas sensors. The enhanced gas sensing properties due to the synergic interaction between intimately contacted polypyrrole and vanadium oxide nanotubes lead to the formation of a hetero p-n junction with a depletion region, which is similar to a field effect transistor. The gas effects a change of the depletion region and thus modulates the conductivity of the junction.     

支化聚吡咯甲烷的制备与光学性能

聚吡咯的溶解性较差,为其光学性能研究带来了诸多困难.将吡咯类和苯甲醛类单体通过缩聚反应可制备出具有较好溶解性的聚吡咯甲烷发光材料.以吡咯和对二甲氨基苯甲醛为原料,对苯二甲醛为支化单体,采用溶液共缩聚法制备了不同原料比的支化聚吡咯甲烷,并对其光学性能进行了研究.结果 表明,支化聚吡咯甲烷的热稳定性较好,高于300℃后出现...     

Amperometric immunosensor for the detection of anti-West Nile virus IgG

An amperometric immunosensor for the detection of West Nile virus (WNV) IgG was developed. This device was based on the immobilization of T7 phages, which were modified by an additional peptide sequence taken from the virus and used as antigen. The electropolymerization of a phage-amphiphilic pyrrole ammonium mixture previously adsorbed on the electrode surface provided an efficient entrapment of phages in a polypyrrole film. After incubation with a secondary peroxidase-labeled antibody, the immunosensors were applied to the quantitative amperometric determination of WNV-antibody at 0 V vs Ag/AgCl via the reduction of the enzymically generated quinone in the presence of hydroquinone and H2O2. The optimum immunosensor configuration detected low WNV-antibody dilutions down to a titer of 1:10(7) with an excellent regeneration of the immunosensor response by glycine treatment.     

Increasing surface capacity for on-probe affinity capture MALDI-MS via gold particle attachment to allyl amine plasma polymers

In this study, we demonstrate that the protein binding capacity of a surface modified matrix-assisted laser desorption/ionization (MALDI) target can be increased significantly by architecturing the surface of the MALDI probe using gold microparticles. In the present approach, a MALDI target, initially modified via pulsed rf plasma deposition of an allyl amine polymer thin film, is subsequently architectured via reaction with 2-iminothiolane and surface attachment of gold microparticles. The modified probe is then exposed to thiolated biotin to introduce an avidin binding element on the surface of the gold beads. The protein binding capacity of this architectured target is compared with a similarly plasma polymer modified MALDI target that is directly biotinylated. Application of various surface concentrations of avidin to the two probes and MALDI-MS analysis of avidin contained in the solution removed from the probe reveals that saturation of the gold-particle architectured target occurs at a factor of 15-30 higher applied surface concentration, as compared with the unarchitectured target. Furthermore, MALDI-MS analysis of the avidin retained on the two probes reveals that the limit of detection is lowered by a factor of 15-20 on the gold-particle architectured target as compared with the unarchitectured target.