Electrochemical synthesis and optimization of poly(4-methoxyphenol) film as a sensor material

This article describes that electrochemical polymerization of 4-methoxyphenol in the presence of enzyme glucose oxidase produces adherent polymeric films containing the active enzyme onto the surface of platinum electrodes. Polymeric electrodes prepared in this one-step procedure can be operated for the glucose determination. The effects of the electrochemical polymerization parameters (for example, concentrations of monomer, electrolyte, and enzyme; film thickness; and polymerization potential) on the electrode preparation and the effects of amperometric measurement parameters (for example, pH, temperature) on the amperometric responses to the glucose of the prepared electrodes were systematically investigated, and optimal values were determined. Furthermore, glucose specificity and storage stability of the enzyme electrode were investigated. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 1941–1947, 1998     

Preparation and sensor properties of poly (o-toluidine) film

Summary An amperometric biosensor for glucose was constructed in a one-step procedure by the electropolymerization of o-toluidine in the presence of glucose oxidase on Pt substrates in KCl aqueous electrolyte at a potential of 0.5 V vs Ag / AgCl. The amperometric responses of the prepared polymeric biosensor to the glucose were measured at a potential of 0.7 V in PBS solution. Results showed that this polymeric sensor exhibited a fast amperometric response time (4–5 s) and a linear range up to 6 mM glucose with poor stability. Also, it was seen that biosensor responded successfully to glucose injections in the presence of some interfering species such as lactose, sucrose and urea. Received: 27 January 1999/Revised version: 18 May 1999/Accepted: 18 May 1999     

Covalent immobilization of glucose oxidase to poly(O‐amino benzoic acid) for application to glucose biosensor

A biosensor for glucose utilizing glucose oxidase (GOX) covalently coupled to poly(o‐amino benzoic acid) (PAB; a carboxy‐group‐functionalized polyaniline) is described. Amperometric response measurements conducted via unmediated and mediated (with ferrocene carboxylic acid and tetrathiafulvalene) reoxidation of GOX show that glucose can be detected over a wide range of concentrations. An enzyme‐conducting polymer‐mediator model provides for better charge transport in a biosensor. The optimal response, obtained at pH 5.5 and 300 K, lies in the 1–40 mM range. A kinetic plot yields the value of the apparent Michaelis–Menten constant, K_m^app. The operational stability of the PAB‐based glucose biosensor was experimentally determined to be about 6 days. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 662–667, 2000     

New application of cross-linked poly(N-bromoacrylamide) and poly(N-bromosuccinimide) as highly efficient and chemoselective heterogeneous polymeric catalysts for deprotection of 1,3-dithianes and 1,3-dithiolanes under mild conditions

Cross-linked poly(N-bromoacrylamide) (PNBA) and poly(N- bromosuccinimide) as the mild and efficient heterogeneous polymeric catalysts were applied for selective deprotection of 1,3-dithianes and 1,3-dithiolanes to their corresponding carbonyl compounds. They were also effective as a reagent in aqueous media. These methods are very simple and the polymer catalysts could be recycled several times. Deprotection of thioacetal and thioketal without enolizable hydrogens proceeded very well to give only the corresponding aldehyde and ketone in high to excellent yield. Nevertheless, in the case of thioketals carrying enolizable hydrogens, deprotection accompanied with the formation of a minor ring-expanded product is observed. However, using the PNBA/H₂O system, ring expansion of these thiolketals with enolizable hydrogen was not detected. These methods provide advantages, such as chemoselectivity, easy preparation, simple work up, excellent yields, and the ability to recycle the catalyst, which makes this method more useful compared to other known methodologies.     

Ultrasound‐accelerated dehydrogenation of poly(1,3‐cyclohexadiene): efficient synthesis of poly(para‐phenylene)

The effect of ultrasonication on the dehydrogenation of poly(1,3‐cyclohexadiene) (PCHD) with benzoquinones was examined with the aim of improving the rate of reaction at moderate temperature. The type of solvent and the ultrasound treatment strongly affected the dehydrogenation of PCHD. The rate of reaction of the dehydrogenation of PCHD with 2,3‐dichloro‐5, 6‐dicyano‐1,4‐benzoquinone (DDQ) or 3,4,5,6‐tetrachloro‐1,2‐(o)‐benzoquinone (TOQ) was markedly improved by the use of ultrasound, and poly(para‐phenylene) (PPP) and PPP–TOQ complex, respectively, were successfully obtained. The electron drift mobility for PPP was of the order of 10^?4 cm² V^?1 s^?1 with a negative slope, while that for PPP–TOQ complex was of the order of 10^?3 to 10^?4 cm² V^?1 s^?1 with a negative slope. The dehydrogenation of PCHD with benzoquinones under ultrasonication is thus an effective method to obtain soluble PPP with a well‐defined polymer chain structure. Copyright © 2010 Society of Chemical Industry     

Comparative study of poly(vinyl alcohol)‐based support materials for the immobilization of glucose oxidase

BACKGROUND: The performances of four types of glucose oxidase (GOD) immobilization materials based on poly(vinyl alcohol) (PVA) were compared. The matrices of interest were chemically‐linked PVA, freeze‐thawed PVA cryogel, tetramethoxysilane (TMOS) sol‐gel‐PVA hybrid material, and alumina sol‐gel‐PVA hybrid material. RESULTS: Overall, the membranes showed good sensitivity except for the chemically cross‐linked PVA. However, the main differences with the enzyme immobilization methods were enzyme leakage and values of K_m^app. CONCLUSION: Freeze‐thawed PVA‐GOD membranes and TMOS‐PVA, which showed satisfactory sensitivity and adequate value of K_m^app, were quite promising as support materials for immobilizing GOD. Copyright © 2007 Society of Chemical Industry     

Chitosan‐grafted poly(hydroxyethyl methacrylate‐co‐glycidyl methacrylate) membranes for reversible enzyme immobilization

Epoxy group‐containing poly(hydroxyethyl methacrylate/glycidyl methacrylate), p(HEMA/GMA), membrane was prepared by UV initiated photopolymerization. The membrane was grafted with chitosan (CH) and some of them were chelated with Fe(III) ions. The CH grafted, p(HEMA/GMA), and Fe(III) ions incorporated p(HEMA/GMA)‐CH‐Fe(III) membranes were used for glucose oxidase (GOD) immobilization via adsorption. The maximum enzyme immobilization capacity of the p(HEMA/GMA)‐CH and p(HEMA/GMA)‐CH‐Fe(III) membranes were 0.89 and 1.36 mg/mL, respectively. The optimal pH value for the immobilized GOD preparations is found to have shifted 0.5 units to more acidic pH 5.0. Optimum temperature for both immobilized preparations was 10°C higher than that of the free enzyme and was significantly broader at higher temperatures. The apparent K_m values were found to be 6.9 and 5.8 mM for the adsorbed GOD on p(HEMA/GMA)‐CH and p(HEMA/GMA)‐CH‐Fe(III) membranes, respectively. In addition, all the membranes surfaces were characterized by contact angle measurements. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3084–3093, 2007     

Electropolymerization of 4-nitro-1,2-phenylenediamine and electrochemical studies of poly(4-nitro-1,2-phenylenediamine) films

In this work, we report the anodic electropolymerization of 4-nitro-1,2-phenylenediamine (4NoPD) in different supporting electrolytes at different pH. The feasibilities of forming the polymer poly(4-nitro-1,2-phenylenediamine) (P4NoPD) on gold and glassy carbon electrodes (GCE) were shown. The P4NoPD films were generated by continuous potential cycling between −0.15 V and +1.10 V (versus Ag|AgCl, saturated KCl). The pH of the electropolymerization medium, the nature of the background electrolyte and the number of cycles used were found to influence strongly the amount of polymer deposited. The reduction of nitro-groups of the P4NoPD films was also found to be dependent on solution conditions, especially pH.     

Preparation,characterization and biodegradable characteristics of poly(1,3-trimethylene carbonate-co-glycolide)

Poly(1,3-trimethylene carbonate-co-glycolide) (PGCA) has been synthesized by ring-opening polymerization of 1,3-trimethylene carbonate (CA) and glycolide (GA) with stannous octoate as catalyst. The copolymers were characterized by ¹H nuclear magnetic resonance (NMR), ¹³C NMR and differential scanning calorimetry. Water content and static contact angle of distilled water on the polymer surface were used to evaluate the hydrophobicity of the copolymers. There was no apparent difference in hydrophobicities of copolymers containing up to 30 mol% GA. The biodegradation of PGCA was conducted in phosphate buffer solution at 37°C and in rats. The results indicated that the degradation rates of PGCA were higher than that of PCA and depended on the GA fraction in the copolymers. Furthermore, degradation occurred in the bulk when the GA content exceeded 20 mol%. With less GA units the degradation became a surface reaction both in vitro and in vivo. These properties of PGCA may be useful in protein delivery systems.     

Poly(2,5‐dimethoxyaniline) films on mild steel for application to glucose biosensor

Poly(2,5‐dimethoxyaniline) (PDMA) films were electrochemically synthesized on mild steel from an aqueous oxalic acid solution using galvanostatic mode. These films were characterized by potential–time curve, UV‐visible absorption spectroscopy, Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM). The enzyme glucose oxidase (GOx) was entrapped into the PDMA film by a physical adsorption method. The resulting PDMA–GOx films were characterized by UV‐visible absorption spectroscopy, FTIR, and SEM. The amperometric response of the PDMA–GOx films was measured as a function of glucose concentration in phosphate buffer solution (pH 7.3). The PDMA–GOx films exhibit a fast and linear amperometric response in the range of 2–20 mM glucose. The maximum current density and Michaelis–Menten constant of PDMA/GOx films are found to be ～483 μA/cm² and 1.12 mM, respectively. The shelf stability and thermal stability of these films were also investigated. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

Crosslinked poly(vinyl alcohol) supports for the immobilization of a lipolytic enzyme

Different esters of crosslinked poly(vinyl alcohol) (PVA) were synthetized. They were developed for protein fractionation and immobilization. PVA was crosslinked with epichlorohydrin (CL‐PVA) and esterified with linear fatty acids of different length (Cn‐CL‐PVA). A characterization of the obtained products was made. The swelling behavior, the solubility, and the percentage of esterification were examined. Values of equilibrium water content of about 81% were reached for CL‐PVA samples. The polymers' stability and morpholgy were also investigated. Thermal analysis showed an increase in matrices stability, while SEM data showed the superficial development due to crosslinking and esterification reactions. Moreover, evident morphological inhomogeneities, mainly in the commercial and crosslinked products rather than in the final polymer, were present. Finally, immobilization experiments with a commercial crude of Candida rugosa were performed. Experiments showed a greater affinity of the protein for carbon chain length ranging from 8 to 12. Data indicated that compared to Celite 545, C8‐CL‐PVA was a better support for enzyme immobilization by physical adsorption, confirming the fact that microbial lipases prefer hydrophobic supports. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 1881–1889, 1999     

Insulin release dynamics from poly(diethylaminoethyl methacrylate) hydrogel systems

Novel glucose‐sensitive systems for the release of insulin from poly(diethylaminoethyl methacrylate) (PDEAEM) microparticles and nanoparticles decorated with glucose oxidase and catalase enzymes have been developed. The effect of polymer composition and loading conditions on the insulin loading efficiency and release was studied. The optimal conditions for loading insulin into PDEAEM microparticles were found to be at a loading pH of 5.6, particle to insulin mass ratio of 7:1, a concentration of 1.0 mg/mL insulin, and a collapsing pH of approximately 9.5. Microparticles exhibited a responsive (pH) or intelligent (glucose) release of insulin from a stimulus. Microparticles that had a nominal crosslinking ratio of 10% released a third of the insulin payload after a single stimulus, compared to nearly 70% for microparticles with a 3% crosslinking ratio. PDEAEM microparticles of 150 μm diameter showed promise as components of a system of automated, intelligent delivery method for insulin to type I diabetics. © 2013 American Institute of Chemical Engineers AIChE J, 59: 3578–3585, 2013     

一株聚乙烯醇降解酶产生菌的产酶条件优化

枯草芽胞杆菌WSH-062在摇瓶培养中能产生胞外的PVA降解酶。通过单因素及正交实验对其进行了发酵条件的优化。研究结果表明:该菌产生的PVA降解酶为诱导型酶;2 g/L的复合氮源(NaNO3和酵母粉的配比为1∶1)就能满足细胞生长和产酶的营养需要。正交实验分析得到最优的发酵培养基为:PVA 30 g/L,酵母粉12.2 g/L,NaNO3 10.1 g/L,MgSO4.7H2O 0.35 g/L,KH2PO4 3 g/L,pH值7.2。优化之后的PVA降解酶酶活达到5.00 U/mL,比优化前提高了4.75倍,并且重复性较好。     

A new metal chelate sorbent for glucose oxidase: Cu(II)- and Co(II)-chelated poly(N-vinylimidazole) gels

Poly(N-vinylimidazole) (PVIm) gels were prepared by irradiating a binary mixture of N-vinylimidazole (VIm)–water in a ⁶⁰Co-γ source having 4.5 kGy/h dose rate. In the glucose oxidase (GOx) adsorption studies, affinity gels with a swelling ratio of 1100% for PVIm and 40 and 55% for Cu(II)- and Co(II)-chelated PVIm gels, respectively, at pH 6.5 in phosphate buffer were used. FTIR spectra were taken for PVIm and Cu(II)- and Co(II)-chelated PVIm, and glucose oxidase adsorption on these gels, to characterize the nature of the interactions in each species. The results show that PVIm–glucose oxidase interaction is mainly electrostatic and metal ion–chelated PVIm gel–glucose oxidase interaction is of coordinate covalent nature. Cu(II) and Co(II) ions were chelated within the gels via amine groups on the imidazole ring of the gel. Different amounts of Cu(II) and Co(II) ions [maximum 3.64 mmol/g dry gel for Cu(II) and 1.72 mmol/g dry gel for Co(II)] were loaded on the gels by changing the initial concentration of Cu(II) and Co(II) ions at pH 7.0. GOx adsorption on these gels from aqueous solutions containing different amounts of GOx at different pH was investigated in batch reactors. GOx adsorption capacity was further increased when Cu(II) and Co(II) ions were attached [up to 0.53 g GOx/g dry Co(II)-chelated PVIm gels]. More than 90% of the adsorbed GOx was desorbed in 5 h in desorption medium containing 1.0M KSCN at pH 7.0 for plain gel and 0.05M EDTA at pH 4.9 for metal-chelated gel. Nonspecific glucose oxidase adsorption on/in the metal ion–chelated PVIm gel was investigated using 0.02M of phosphate buffer solution. The nonspecific GOx adsorption was determined to be about 18% for PVIm and 8% for the metal ion–chelated PVIm gels. The ionic strength effect was investigated both on PVIm and on the metal ion–chelated PVIm gels for the glucose oxidase adsorption. It was found that ionic strength was more effective on the PVIm gel because of the electrostatic interaction between protonated gel and the deprotonated glucose oxidase side chain. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 446–453, 2001     

Crystallization of polyformals: 1. Crystallization kinetics of poly(1,3-dioxolane)

Poly(1,3-dioxolane) fractions ranging in molecular weight from 8800 to 120 000 have been isothemally crystallized in the temperature range 25–41°C. From the dilatometric isotherms, the Avrami exponent is an integral number, 3, and is independent of temperature and molecular weight. The level of crystallinity is dependent on molecular weight and there is a change from ～55% for the highest molecular weight fraction to ～80% for the lowest molecular weight fraction. The overall crystallization rate temperature coefficient was studied using two dimensional nucleation theory and it was found that the interfacial free energies do not change with molecular weight. However, the usual plots are nonlinear in the whole range of crystallization temperatures. For the high crystallization temperatures the slope is about twice the low crystallization temperature slope, this change being related to a morphological transition.     

Application of poly(<Emphasis Type="Italic">o</Emphasis>-phenylenediamine) in rechargeable cells

The electrochemical synthesis of poly(o -phenylenediamine) (PoPD) from an aqueous medium was suitably modified by controlling the switching potential to enhance the growth of the polymer. The charge–discharge data for the cell Zn/1 M ZnSO₄ (pH 4)/PoPD are presented. The polymer was modified by incorporating Pt microparticles into its matrix during electropolymerization. The PoPD-Pt composite electrode was also characterized as a cathode active material in aqueous cells.     

Poly(Pyrrole)-Poly(N-Methylpyrrole) Composite Matrix for Amperometric Biosensor Design

Electrochemical copolymerization of pyrrole–N-methyl pyrrole has been carried out galvanostatically on platinum substrate. The polypyrrole–poly (n-methylpyrrole) composite films were subjected to electrical, spectral and morphological characterizations. Glucose biosensor was further fabricated based on the immobilization of glucose–oxidase in the composite films by crosslinking via glutaraldehyde. The effect of phosphate and acetate buffer was investigated. The biosensor exhibited an excellent linear response for a wide range of glucose concentration from 0 mM to 50 mM in both the buffers at pH 7.4. However, the sensitivity of the developed biosensor in the presence of a phosphate buffer was found to be higher.     

Electrochemical immobilization of ascorbate oxidase in poly(3,4‐ethylenedioxythiophene)/multiwalled carbon nanotubes composite films

Immobilization of ascorbate oxidase (AO) in poly(3,4‐ethylenedioxythiophene) (PEDOT)/multiwalled carbon nanotubes (MWCNTs) composite films was achieved by one‐step electrochemical polymerization. The PEDOT/MWCNTs/AO modified electrode was fabricated by the entrapment of enzyme in conducting matrices during electrochemical polymerization. The PEDOT/MWCNTs modified electrodes were investigated by cyclic voltammetry and electrochemical impedance spectroscopy. The experimental results showed that the composite films exhibited better mechanical integrity, electrochemical activity, higher electronic and ionic conductivity, and larger redox capacitance compared with pure PEDOT films, which would be beneficial to the fabrication of PEDOT/MWCNTs/AO electrochemical biosensors. The scanning electron microscopy studies revealed that MWCNTs served as backbone for 3,4‐ethylenedioxythiophene (EDOT) electropolymerization. Furthermore, the resulting enzyme electrode could be used to determine L ‐ascorbic acid successfully, which demonstrated the good bioelectrochemical catalytic activity of the immobilized AO. The results indicated that the PEDOT/MWCNTs composite are a good candidate material for the immobilization of AO in the fabrication of enzyme‐based biosensor. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Electrochemical synthesis of poly(methylsilyne) and investigation of the effects of parameters on the synthesis

This study aims to synthesize poly(methylsilyne) by electrochemical reduction of methyltrichlorosilane at a constant potential of ?6 V, while investigating the effects of parameters such as the nature of the electrode, solvent and supporting electrolyte, the monomer/solvent ratio, and the reaction time on the properties of the products. The polymer was characterized by ¹H‐NMR (Proton Nuclear Magnetic Resonance Spectroscopy), FTIR (Fourier Transform Infrared Spectroscopy), UV‐Visible Spectroscopy, and TGA (Thermogravimetry Analysis). Copper (Cu) electrodes were used as stainless steel introduced impurities into the system. In an electrolytic media consisting of acetonitrile (AN), sodium dodecyl sulfate (SDS), and Cu electrodes, increasing the monomer/solvent ratio and the reaction time affected the system negatively based on the purity of poly(methylsilyne) in the final product. Reproducible results were only achieved in an electrolytic media containing 1,2‐dimethoxyethane (DME) and tetrabutylammonium perchlorate (TBAP). In this system, the purity of the products was less dependent on monomer/solvent ratio and reaction time. The color and the ¹H‐NMR, FTIR, and UV‐Visible spectra proved that the product is poly(methylsilyne). In addition, the significantly high‐average decomposition temperature obtained from TGA results revealed that the polymer is a good candidate as an additive for improving thermal stability and flame retardancy in thermoplastics. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

One‐step synthesis of bis‐macromonomers of poly(1,3‐dioxolane) catalyzed by Maghnite‐H+

Telechelic poly(1,3‐dioxolane) (PDXL) bis‐macromonomers bearing methyl methacrylate end groups were prepared by cationic ring‐opening polymerization of 1,3‐dioxolane (DXL), in the presence of methacrylic anhydride, catalyzed by Maghnite‐H⁺ (Mag‐H⁺), in bulk and in solution. Maghnite is a montmorillonite sheet silicate clay, which exchanged with protons to produce Mag‐H⁺. The influence of the amount of Mag‐H⁺, monomer (DXL), and methacrylic anhydride on monomer conversion was studied. The polymerization yield and the molecular weight of α,ω‐bis‐unsaturated PDXLs prepared depend on the amount of Mag‐H⁺ used and the reaction time. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006