Electropolymerization, biosensor electrodes

Entrapment of biochemically reactive molecules into conductive polymer substrates is being used to develop electrochemical biosensors (212). This has proven especially useful for the incorporation of enzymes that retain their specific chemical reactivity. Electropolymerization of pyrrole in an aqueous solution containing glucose oxidase (GO) leads to a polypyrrole in which the GO enzyme is co-deposited with the polymer. These polymer-entrapped GO electrodes have been used as glucose sensors. A direct relationship is seen between the electrode response and the glucose concentration in the solution which was analyzed with a typical measurement taking between 20 to 40 s. 

Z. Zhang, H. Liu, and J. Deng, A glucose biosensor based on immobilization of glucose oxidase in electropolymerized o-aminophenol film on platinized glassy carbon electrode. Anal. Chem. 68, 1632-1638 (1996). 

X. Xu, J.Q. Zhao, D.C. Jiang, J.L. Kong, B.H. Liu, and J.Q. Deng, Ti02 sol-gel derived amperomet-ric biosensor for H202 on the electropolymerized phenazine methosulfate modified electrode. Anal. Bioanal. Chem. 374, 1261-1266 (2002). 

F. Palmisano, R. Rizzi, D. Centonze and P.G. Zambonin, Simultaneous monitoring of glucose and lactate by an interference and cross-talk free dual electrode amperometric biosensor based on electropolymerized thin films, Biosens. Bioelectron., 15(9-10) (2000) 531-539. 

R. Garjonyte and A. Malinauskas, Glucose biosensor based on glucose oxidase immobilized in electropolymerized polypyrrole and poly(o-phe-nylenediammine) films on a Prussian blue-modified electrode, Sens. Actuators B, 63 (2000) 122-128. 

Geise RJ, Adams JM, Barone NJ, Yacynych AM. Electropolymerized films to prevent interferences and electrode fouling in biosensors. Biosensors Bioelectronics 1991, 6, 151-160. 

Electropolymerized films have been used to prevent interferences and fouling in biosensors constructed from reticulated vitreous carbon and platinum disk electrodes (14,15). A biosensor constructed using electropolymerized films can have significantly improved diffusional properties due to the thinness of the film. By engineering the components and properties of a biosensor on a microscopic scale, rather than using "bulk-technology" and physically assembling discrete macroscopic components, as is the conventional practice, an all-chemical method of construction can be achieved. All-chemical methods of construction would... 

Procedure-Electron-Mediated Biosensor. 1,3-DAB was electropolymerized onto the graphite from a 3 mM solution in phosphate buffer using cyclic voltammetry. The potential was cycled from 0.00 V to +0.80 V and back to 0.00 V (vs SCE) at 5 mV/s for twelve scans. l,r-dimethylferrocene (1,1 -DMF) was adsorbed onto an inverted electrode. Three successive drops of a saturated solution (10 pL each) were added to the surface and each was allowed to air dry before applying the next drop. The electrode was rinsed with water after application of each drop. 

Through the combination of SPR with a - poten-tiostat, SPR can be measured in-situ during an electrochemical experiment (electrochemical surface plasmon resonace, ESPR). Respective setups are nowadays commercially available. Voltammetric methods, coupled to SPR, are advantageously utilized for investigations of - conducting polymers, thin film formation under influence of electric fields or potential variation, as well as - electropolymerization, or for development of -> biosensors and - modified electrodes. Further in-situ techniques, successfully used with SPR, include electrochemical - impedance measurements and -+ electrochemical quartz crystal microbalance. 

Their biosensor consisted in a Pt wire on which GOD was immobilized by the electropolymerization of m-phenylenediamine. The advantage of this type of immobilization consists in creating an effective barrier against electrochemical interference due to the polymer formed onto the electrode. Moreover, an extended linearity for the glucose sensor was also obtained, and this was a requisite for the direct measurement of the subcutaneous glucose at diabetic levels, since in practice an extremely low dilution of the subcutaneous fluid was realized. 

Applications. A biotinylated GOX-based biosensor was developed based on a new electropolymerized material consisting of a pol3rp3uidyl complex of ruthenium(II) functionalized with a pyrrole group [90]. Because histidine, lysine and arginine functions also coordinate Os /Os , biosensors based on co-electrodeposited GOX, HRP, soybean peroxidase (SBP) and laccase with redox Os /Os polymer have been developed [89]. A metal chelate formed by nickel and nitrilotriacetic acid was used to modify a screen-printed electrode surface. The functionalized support allowed stable attachment of acetylcholinesterase and the resulting biosensor was used for sensitive detection of organophosphorus insecticides [91]. This method is attractive because it ensures a controlled and oriented enzyme immobilization, considerably improving the sensitivity and the detection limit. 

This section discusses the reactivities and biosensor applications of functionalized electrosynthetic polyanilines prepared by (i) electropolymerization and (ii) chemical polymerization of aniline on the surfaces of Au, glassy carbon or Pt disk electrodes. Four such polyaniline or substituted composite polyaniline films developed by our research group are (a) nanofibrillar polyaniline-polyvinyl sulfonate (PANI-PVS), (b) poly(2,5-... 

One successful strategy to improve ET rates between enzyme and electrode is the modification of conducting polymers with redox mediators in order to obtain reagentless biosensors [11, 270, 271, 292-299]. The drawback of electropolymerization of conducting polymers is that the reaction is sensitive to oxygen, which complicates fabrication at the industrial scale. 

Using Electropolymerized Films to Form Enzyme Electrode Biosensors. . 402... 

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