T. Inagaki

A glucose electrode based on carbon paste chemically modified with a ferrocene-containing siloxane polymer and glucose oxidase, coated with a poly(ester-sulfonic acid) cation-exchanger

Abstract A carbon-paste chemically modified with glucose oxidase and a ferrocene-containing siloxane polymer was further modified by coating the electrode surface with a poly(ester-sulfonic acid) cation-exchanger, Eastman AQ-29D. The polymer is obtained as a homogeneous aqueous dispersion at pH 5–6; when dried, the polymer coating is not water-soluble. The coating was shown not to be detrimental to the enzyme activity but to prevent electrochemically active anionic interferents such as ascorbate and urate from reaching the electrode surface. The polymer coating also prevented glucose oxidase from leaking out of the carbon paste into the contacting solution and protected the electrode surface from fouling agents present in urine and bovine serum albumin. Uncoated electrodes lost some 10-2-15% of their original response to glucose after storage in buffer for three weeks whereas the response of the coated electrodes remained constant. Calibration curves for glucose were strictly linear up to about 5 mM for uncoated and up to 20 mM for coated electrodes. The response current to glucose was not decreased after coating.

Ordered Langmuir-Blodgett films of polypyrrole and analogs

Abstract Ordered mono and multilayers of polypyrrole and its analogs were prepared using a Langmuir-Blodgett film balance. Films could be transferred with facility and were picked up on microscope grids for electron microscopic studies among a number of other investigations. Scanning electron microscopy (SEM) revealed a smooth coverage over a large surface area of the substrate. Electron diffraction from these thin films revealed that the nature of packing is substantially different from bulk grown polypyrrole.

Chemically modified polypyrrole

Abstract Polypyrrole (PPy) films have been systematically modified with electroactive groups in the β-position to design electrode materials with specific electrochemical and surface active properties. Electrochemical copolymerization of pyrrole and 3-(6-ferrocenyl,6-hydroxyhexyl)pyrrole (P-6-Fc) yields a ferrocene functionalized polypyrrole with a controlled amount of ferrocene functionalization. And also, copolymers of pyrrole and 3-(4-(2,5-dimethoxyphenyl)butyl)pyrrole (P-MP) can be made by electrochemical polymerization and converted to the copolymers containing pH dependent electroactive hydroquinone moieties. Derivatized pyrroles have also been incorporated into Langmuir-Blodgett film structures. The surface pressure-area isotherms of 3-(13-ferrocenyl,13-hydroxytridecyl) pyrrole (P-13-Fc) and the mixed monolayer of P-13-Fc and 3-n-hexadecylpyrrole (HDP) are shown.

Electrochemical Polymerization of Pyrrole Derivatives

Abstract Electrochemical copolymerization of pyrrole and 3-(6-ferrocenyl-6-hydroxyhexyl)pyrrole (P-Fc) yields a ferrocene functionalized polypyrrole with a controlled amount of ferrocene functionalization. Similarly, copolymers of pyrrole and 3-(4-(2,5-dimethoxyphenyl)butyl)pyrrole (P-MP) can be made by electrochemical polymerization and converted to the copolymers containing pH dependent electroactive hydroquinone moieties.

Ferrocene-Modified Siloxane Polymers as Electron Relay Systems in Amperometric Glucose Sensors

Abstract This paper describes the design and testing of amperometric glucose sensors in which electrical communication between the flavin redox centers of glucose oxidase and an electrode is achieved via a network of donor-acceptor relays chemically bound to a flexible siloxane polymer backbone. Procedures are discussed for the synthesis of a variety of mediator(ferrocene)-containing siloxane copolymers which differ in flexibility and in the spacing between redox moieties, and for the optimization of the interaction between the flavin redox centers of glucose oxidase and the polymer-bound electron transfer relay system through investigation of these new flexible polymers in glucose sensors.

Orientational behavior of thin films of poly(3-methylthiophene) on platinum: A FTIR and NEXAFS study

Abstract Near edge x-ray absorption fine structure (NEXAFS) and infrared reflection-absorption spectroscopy (IRRAS) have been used to study the orientational behavior of thin films of poly(3-methylthiophene) electrochemically polymerized on a platinum surface. Clear orientational effects, with the thiophene rings predominantly oriented parallel to the platinum surface, were observed when the thickness of the polymer films were within a few hundred A. It was found that more highly ordered films were produced at lower polymerization potential (1.4V vs SCE) than at higher potential (1.8V vs SCE).

Orientational Effects in 3-n-Hexadecylpyrrole Langmuir-Blodgett films

Abstract 3-n-hexadecylpyrrole have been synthesized, and Langmuir-Blodgett films of this compound have been studied by means of transmission and grazing incident reflection FT-IR spectroscopy. A comparison of the spectra at the two different polarizations shows that the hydrocarbon tails are oriented normal to the substrate surface for multilayer LB films. For the single monolayer LB films, the hydrocarbon tails are tilted with respect to the substrate surface possibly due to interactions between the pyrrole head groups and the platinum substrate.

Langmuir-Blodgett films of a pyrrole and ferrocene mixed surfactant system

The Langmuir-Blodgett technique was used to study the molecular organization of a mixed 3-hexadecyl pyrrole (3HDP) and ferrocene-derivatized pyrrole (Fc-Py) surfactant system. It has been determined that stable monolayer films of the mixed system could be formed at the air-water interface. The growth and assembly process led to polypyrrole 2-D lattices with heretofore unsurpassed order. In fact, the process of template polymerization, it appears, leads to a new crystal phase for the polypyrrole component of the thin film structure. Various monolayer and multilayer films were prepared on platinum-coated substrates for surface spectroscopic characterization. Near Edge X-Ray Absorption Fine Structure (NEXAFS) studies revealed that highly ordered multilayer structures are being formed. Electrochemical studies have been initiated to determine the feasibility of these films in molecular electronic device applications.

An Infrared Reflection Spectroscopy Study of Orientational Behavior in Poly(3-methylthiophene) on a Pt Surface

Infrared reflection-absorption spectroscopy (IRRAS) has been used to obtain the vibrational spectra of thin films of poly(3-methylthiophene) electrochemically polymerized on a platinum surface. Clear orientational effects, with the thiophene rings oriented parallel to the platinum surface, were observed when the thickness of the polymer films were within a few hundred Angstroms. 17 refs., 4 figs.

Flavoenzyme-based biosensors with redox polymer electron relays

A description is given of the design and testing of a class of amperometric bioanalytical sensor in which electrical communication between the flavin redox centers of an oxidase and a conventional electrode is achieved by means of a network of donor-acceptor relays chemically bound to a flexible siloxane polymer. Electrochemical results demonstrating this mediated electrical communication are discussed for several polymer/enzyme systems. The molecular weight range for these redox-containing polymeric materials is approximately 2000-10000. Purification of the polymers was achieved by reprecipitation from chloroform solution by dropwise addition to a large excess amount of acetonitrile at room temperature. This reprecipitation was repeated two to three times to ensure that no low-molecular-weight species (which could act as freely diffusing electron transfer mediators) were present. Redox-polymer/glucose-oxidase/carbon-paste electrodes were tested and found to be sensitive to small changes in glucose concentration over a clinically useful range of concentrations.<<ETX>>