Coating metals on cellulose–polypyrrole composites: A new route to self-powered drug delivery system

A self-powered drug delivery system based on cellulose–polypyrrole (PPy) composite film was developed. The cellulose–PPy composite film was prepared by deposition of drug-contained PPy film on the inner and outer surfaces of a porous cellulose film. After coating a thin layer of active metal such as magnesium on the one side of the composite film, the drug stored in the PPy film can be released autonomously upon exposure to the electrolyte solution. It was confirmed that the drug release from the system followed the galvanic cell mechanism. The amount of the drug released and the release rate of drug can be controlled by adjusting the thicknesses and types of the active metals, respectively. Since the cellulose film is biodegradable and the system obtained is flexible and lightweight, it is therefore expected that this drug delivery system can find in vivo applications.     

Biomolecules-carbon nanotubes doped conducting polymer nanocomposites and their sensor application

A simple method for preparing bio-functionalized soluble single-walled carbon nanotubes (SWNTs) is described. Different proteins such as bovine serum albumin (BSA), cytochrome c and horseradish peroxidase (HRP) were used to solubilize low functionality SWNTs in water aided by sonication. The unbound proteins were removed by column chromatography and the SWNT-protein conjugate was used as the sole anionic dopant in electropolymerization of polypyrrole from polymerization solution at pH above the isoelectric point of the protein to provide a negative charge. The morphology of the polypyrrole with SWNT-protein dopant was found to be three-dimensional and fibrous with wide open interlocking pores in contrast to smooth and cauliflower-like for chloride doped polypyrrole. Enhanced sensor performance was demonstrated for hydrogen peroxide detection on polypyrrole/SWCNT-HRP nanocomposites modified electrode. Such nanocomposites can be potentially applied for other biosensor and bio-fuel cell applications.     

A New Technique for Chemical Deposition of Pt Nanoparticles and its Applications on Biosensor Design

A new glucose biosensor design based on glucose oxidase (GOD) immobilized by polypyrrole has been described in this paper. The polymerization of pyrrole was initiated by a hexachloroplatinate which itself was reduced into Pt nanoparticles and thus served as a catalyst for the H₂O₂ oxidation. Properties of the produced GOD modified electrode were examined and the activity of the entrapped enzyme was determined by basic application on the amperometric detection of glucose. Much better results were found comparatively with the enzyme electrode for which the enzyme was entrapped by the electrochemically polymerized polypyrrole. This kind of technique for Pt nanoparticles deposition can be generalized to many cases where polypyrrole is used.     

Synthesis and Characterization of Some N-substituted Polypyrrole Derivatives: Towards Glucose Sensing Electrodes

Synthesis and chemical oxidative polymerization of some N-substituted pyrroles ((N-Py)s) were carried out using Clauson-Kaas method and FeCl₃ in CHCl₃ medium, respectively. The produced polymers, N-(p-benzoic acid)polypyrrole (NpbPPy); N-(o-aminophenyl)polypyrrole (NoaPPy); N-(m-nitrophenyl) polypyrrole (NmnPPy), were characterized by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) analysis. An enzymatic glucose biosensor is fabricated through immobilizing glucose oxidase (GOX) into N-substitued polypyrrole matrixes. The parameters affecting the fabrication and experimental conditions of biosensors were optimized. The best biosensor results were obtained for NpbPPy matrix. The sensitivity of the proposed biosensor permitted the determination of glucose in the concentration range of 0–9.2 M with a detection limit of 1× 10^{? 6}. The apparent Michaelis–Menten constant (K_M ^app) for the sensor was found to be 25.95 mM.     

Amperometric Glucose Biosensor on Layer by Layer Assembled Carbon Nanotube and Polypyrrole Multilayer Film

An amperometric glucose biosensor on layer by layer assembled carbon nanotube and polypyrrole multilayer film has been reported in the present investigation. Homogeneous and stable single wall carbon nanotubes (SWNTs) and polypyrrole (PPy) multilayer films were alternately assembled on platinum coated Polyvinylidene fluoride (PVDF) membrane. Since conducting polypyrrole has excellent anti‐interference ability, protection ability in favor of increasing the amount of the SWNTs on platinum coated PVDF membrane and superior transducing ability, a layer by layer approach of polypyrrole and carbon nanotubes has provided an excellent matrix for the immobilization of enzyme. The layer‐by‐layer assembled SWNTs and PPy‐modified platinum coated PVDF membrane is shown to be an excellent amperometric sensor over a wide range of concentrations of glucose. The glucose oxidase (GOx) was immobilized on layer by layer assembled film by a physical adsorption method by cross linking through Glutaraldehyde. The glucose biosensor exhibited a linear response range from 1 mM to 50 mM of glucose concentration with excellent sensitivity of 7.06 μA/mM.     

Bioelectrochemical Response of Polypyrrole Modified Urease Sensor

The preparation method of biological ferment electrode is one of decisive factors that affect its bio-electrochemical responding sign. It demands both suitable indicator electrode and antiwater soluble film that can keep catalytic activity. In this paper,urease was doped into polypyrrole(PPy) film while pyrrole(Py) was polymerized by electrochemical method to formed urease biosensor based on PPy film,then,ferment electrode was combined with CO₂ gas-sensing electrode to assemble a urease biosensor responding to urea.     

Chondroitin/polypyrrole nanocomposite hydrogels for the accurate release of 5-fluorouracil by electrical stimulation

The development of electro-stimulated drug release devices is an innovative approach to attain the drug delivery in accurate doses at target sites in a programmed manner. In this work, novel electroactive nanocomposite hydrogels were prepared by encapsulating green-synthesized polypyrrole (PPy) colloids within chondroitin sulfate (CS) networks during the self-crosslinking of CS via N-ethyl-N′-(3-dimethylaminopropyl) carbodiimide chemistry. The structural and morphological properties of CS/PPy hydrogels were studied by Fourier-transformed infrared spectroscopy, scanning electron microscopy, and swelling kinetic measurements. The chemotherapeutic agent 5-fluorouracil (5-FU) was loaded into CS/PPy samples by hydrogel swelling method, or alternatively, by pre-incubating the drug in polymer mixture before crosslinking. Different electrical stimulations can be used to switch ON and accurately tune the 5-FU delivery from GG/PPy hydrogels. A single pulse potential of 5 V switched on the drug delivery up to 90% from nanocomposite hydrogel, in contrast to the low 5-FU amount released in a passive form (< 20%). PPy electroactive behavior played a determining role as the main driving force in 5-FU release activation. Cytotoxicity of hydrogels with and without 5-FU was examined in normal and cancer cells. Considering the high cytotoxicity of 5-FU, the ON/OFF 5-FU release patterns evidenced the potential of CS/PPy hydrogels for electrically controlled drug delivery in implantable or transdermal drug release devices.     

A self-powered and thermally-responsive drug delivery system based on conducting polymers

A simple self-powered drug delivery system was developed based on the galvanic cell mechanism, involving the direct deposition of a drug-contained polypyrrole (PPy) film on the one side of a titanium foil. After covering the other side with a eicosane-poly(l-lactide) (PLLA) blend film, it is interesting to observe that massive drug release only occurred when the release medium was heated to the body temperature. The methyltetrazolium (MTT) assay indicated that the system had good biocompatibility. Since titanium is one of the most commonly used load-bearing implant materials, it is expected that the present drug delivery system can find applications in titanium-related orthopaedic fields.     

Functionalized polypyrrole nanotube arrays as electrochemical biosensor for the determination of copper ions

A novel electrochemical biosensor based on functionalized polypyrrole (PPy) nanotube arrays modified with a tripeptide (Gly-Gly-His) proved to be highly effective for electrochemical analysis of copper ions (Cu²⁺). The vertically oriented PPy nanotube arrays were electropolymerized by using modified zinc oxide (ZnO) nanowire arrays as templates which were electrodeposited on indium–tin oxide (ITO) coated glass substrates. The electrodes were functionalized by appending pyrrole-α-carboxylic acid onto the surface of polypyrrole nanotube arrays by electrochemical polymerization. The carboxylic groups of the polymer were covalently coupled with the amine groups of the tripeptide, and its structural features were confirmed by attenuated total reflection infrared (ATR-IR) spectroscopy. The tripeptide modified PPy nanotube arrays electrode was used for the electrochemical analysis of various trace copper ions by square wave voltammetry. The electrode was found to be highly sensitive and selective to Cu²⁺ in the range of 0.1–30 μM. Furthermore, the developed biosensor exhibited a high stability and reproducibility, despite the repeated use of the biosensor electrode.     

Biosensor on the base of polypyrrole modified ultramicroelectrode arrays

A novel approach for the construction of a micro biosensor on the base of amperometric enzyme microelectrode arrays is described in this paper. The technique contains the electrochemical deposition of different enzymes in a conducting organic polymer, e.g. polypyrrole, on a transducer built up with the help of microfabrication technology. The electrochemical characteristics of these microelectrode arrays can be compared to conventional microelectrodes with the advantage of higher current outputs. For the first time different model enzymes like glucose oxidase, choline oxidase and lactate oxidase have been tested showing the principal possibility to construct a micro biosensor on the base of ultramicroelectrode arrays.     

Investigation of SPR and electrochemical detection of antigen with polypyrrole functionalized by biotinylated single-chain antibody: A review

An electrochemical label-free immunosensor based on a biotinylated single-chain variable fragment (Sc-Fv) antibody immobilized on copolypyrrole film is described. An efficient immunosensor device formed by immobilization of a biotinylated single-chain antibody on an electropolymerized copolymer film of polypyrrole using biotin/streptavidin system has been demonstrated for the first time. The response of the biosensor toward antigen detection was monitored by surface plasmon resonance (SPR) and electrochemical analysis of the polypyrrole response by differential pulse voltammetry (DPV). The composition of the copolymer formed from a mixture of pyrrole (py) as spacer and a pyrrole bearing a N-hydroxyphthalimidyl ester group on its 3-position (pyNHP), acting as agent linker for biomolecule immobilization, was optimized for an efficient immunosensor device. The ratio of py:pyNHP for copolymer formation was studied with respect to the antibody immobilization and antigen detection. SPR was employed to monitor in real time the electropolymerization process as well as the step-by-step construction of the biosensor. FT-IR demonstrates the chemical copolymer composition and the efficiency of the covalent attachment of biomolecules. The film morphology was analyzed by electron scanning microscopy (SEM).Results show that a well organized layer is obtained after Sc-Fv antibody immobilization thanks to the copolymer composition defined with optimized pyrrole and functionalized pyrrole leading to high and intense redox signal of the polypyrrole layer obtained by the DPV method. Detection of specific antigen was demonstrated by both SPR and DPV, and a low concentration of 1 pg mL⁻¹ was detected by measuring the variation of the redox signal of polypyrrole.     

Fabrication of organic phase biosensors based on multilayered polyphenol oxidase protected by an alginate coating

We describe herein, the creation of an organic phase enzyme electrode (OPEE) via avidin–biotin interactions built over an electrogenerated polymer. Multilayered polyphenol oxidase (PPO) assemblies were transferred into an organic solvent (chloroform) for the catechol detection at −0.2 V. In conjunction with an alginate gel, as a hydrophilic additive, the biosensor performance was widely enhanced. The effects of biotinylated polypyrrole film and alginate gel on the diffusion process through the biosensor coating are studied by rotating disk electrode experiments carried out in chloroform with hydroquinone as electroactive permeant.     

Multi-wall carbon nanotubes (MWCNTs)-doped polypyrrole DNA biosensor for label-free detection of genetically modified organisms by QCM and EIS

In this paper, we describe DNA electrochemical detection for genetically modified organism (GMO) based on multi-wall carbon nanotubes (MWCNTs)-doped polypyrrole (PPy). DNA hybridization is studied by quartz crystal microbalance (QCM) and electrochemical impedance spectroscopy (EIS). An increase in DNA complementary target concentration results in a decrease in the faradic charge transfer resistance (R_ct) and signifying “signal-on” behavior of MWCNTs-PPy-DNA system. QCM and EIS data indicated that the electroanalytical MWCNTs-PPy films were highly sensitive (as low as 4 pM of target can be detected with QCM technique). In principle, this system can be suitable not only for DNA but also for protein biosensor construction.     

Conducting polymer-based impedimetric aptamer biosensor for in situ detection

We have successfully developed the first prototype of an electrochemical protein biosensor using polypyrrole as the substrate and doped aptamer as the probe. The sensitivity for a specific target is 10 ng/ml. Two targets, platelet-derived growth factor and immunoglobulin E, have been tested. In both cases the sensor exhibited high specificity and the signal was found to increase as the target concentration increased.     

A stability indicating HPLC method for the determination of electrochemically controlled release of risperidone

A rapid stability indicating reversed-phase high-performance liquid chromatography (HPLC) method is developed for the determination of the electrochemically controlled risperidone release from a novel drug delivery system, based on the intrinsically conducting polymer (ICP), polypyrrole. The chromatographic separation was carried out on a C(18) column using acetonitrile-potassium dihydrogen phosphate (45:55, v/v, pH 6.5; 0.05 M) as the mobile phase. The isocratic flow is at 1.0 mL/min, with a runtime of 6 min, and the UV detection is at 237 nm. This provided a calibration curve linear over the range of 1-100 μg/mL. Intra-day and inter-day accuracy range between 98.4% and 102.6%, and the RSD for precision is <1.43%. The limit of detection and quantitation were determined to be 0.001 μg/mL and 0.01 μg/mL, respectively. The analytical method confirmed risperidone is stable for the oxidizing electric potential and the acidic environment involved during the manufacture and operation of the novel drug delivery system. The rate of risperidone release from polypyrrole depended on electrical stimulation applied to the polymer. This HPLC method is significantly faster than previously published methods and is the first to investigate the effect of an oxidizing potential on risperidone stability, which is essential for the evaluation of controlled delivery from an ICP-based system.     

Development of a platinized and ferrocene-mediated cholesterol amperometric biosensor based on electropolymerization of polypyrrole in a flow system.

The preparation of a cholesterol amperometric biosensor using a platinized Pt electrode as a support for the electropolymerization of a polypyrrole film, in which cholesterol oxidase and ferrocene monocarboxylic acid (electron-transfer mediator) were co-entrapped, is described. All the biosensor preparation steps (platinization and electropolymerization) and the cholesterol determination take place in the same flow system. The presence of the mediator enhances the sensitivity and selectivity of the platinized biosensor without modifying the dynamic parameters of the response, and the platinized layer improves the operational lifetime of the mediated sensor. The sensitivity obtained was 88.51 nA mM(-1) and the limit of detection was 12.4 microM of cholesterol. The analytical properties of the biosensor for the flow-injection determination of cholesterol were studied and compared with those of other more simple amperometric biosensor configurations.     

Direct Visualization and Semi‐Quantitative Analysis of Payload Loading in the Case of Gold Nanocages

Upon incubation with Au nanocages, pyrrole (Py) molecules can enter the cavities by diffusing through the porous walls and then be polymerized to generate a polypyrrole (PPy) coating on the inner surface. The thicknesses of the PPy coating can serve as a direct indicator for the amount of Py molecules that diffuse into the cavity. Py molecules are able to diffuse into the cavities throughout the polymerization process, while a prolonged incubation time increases the amount of Py accumulated on both inner and outer surfaces of the nanocages. Furthermore, it is demonstrated that the dimensions of the cavity and the size of the pores in the wall are not critical parameters in determining the loading efficiency, as they do not affect the thickness of the PPy coating on the inner surface. These findings offer direct evidence to support the applications of Au nanocages as carriers for drug delivery and controlled release.     

A Neural Network Model in the Calibration of Glucose Sensor Based on the Immobilization of Glucose Oxidase into Polypyrrole Matrix

The immobilization of enzymes on an electrode surface is of great importance in bioelectrochemistry. The entrapment of enzymes into a polymer matrix is simple and a speedy technique for the production of biosensors. This procedure of enzyme immobilization by electropolymerization has a great significance in fabrication of micro sensors in the preparation of multiplayer devices. In current study, glucose oxidase enzyme that is specific for the glucose determination was entrapped into polypyrrole matrix containing p‐benzoquinone in PIPES buffer and glucose sensitivity of the biosensor was investigated. Then, artificial neural network analysis was done for the nonlinear calibration plot. This implementation can be used for the sensor failure detection, as well. The estimation power of the neural network used in the direct and inverse calibration modelling was examined by statistical methods. It presented the good performance for the estimation power.     

纳米级微带金电极上葡萄糖氧化酶的固定.性质及应用

实现了葡萄糖氧化酶以及葡萄糖氧化酶和电子传递媒体Fe(CN)^3^-~6同时在纳米级微带电极上的固定,用红外光谱和循环伏安对GOD/PPy微电极进行了表征, 研究了微带金电极上聚吡咯恒电位形成过程的动力学及葡萄糖氧化酶对其动力学过程的影响,探讨了微酶电极GOD/Fe(CN)^3^-~6/PPy对葡萄糖氧化的催化作用, 考察了PPy膜厚度和溶液中氧的存在对GOD/Fe(CN)^3^-~6/PPy微电极测定葡萄糖的影响.     

电活性导电聚合物在生物医学中的应用

以聚吡咯、聚噻吩和聚苯胺为代表的电活性导电聚合物(electroactive conducting polymers,ECP)已成为生物材料、组织工程及临床医学领域关注的焦点.目前研究主要集中在生物相容性、细胞及组织工程、蛋白质分离、DNA吸附修复、可控药物释放、生物传感器、神经探针等方面.ECP在神经细胞、脑细胞、心肌干细胞再生和功能调节,定向诱导组织器官的再生修复方面具有潜在的应用前景.本文主要综述了聚吡咯(PPy)和聚苯胺(PANi)在生物医学领域的研究进展,和电刺激对细胞生长和干细胞分化的影响,并建议了一些前景可观的相关研究方向.