Organic-phase biosensors

Ohmic drop, 32, 88, 105, 129 Operational amplifier, 105 Optically transparent electrode, 40 Organic-phase biosensors, 181 Organic solvents, 102 Organosulfur monolayers, 118 Overvoltage, 14, 121 Oxygen, 75, 87, 103, 177, 190, 193... 

Recent applications of nonconducting polymers, such as PPD and overoxidized poly(pyrrole), as permselective and biocompatible membranes hold great promise for the future of biosensors used for in vivo monitoring. Also the suitability of polymeric films (e.g., Eastman AQ 55) for organic-phase biosensors has led to a new opportunity for amperometric detection of analytes in real nonaqueous matrices. Since enzymes are stable in nonaqueous media, many analytes can be detected amperometrically with organic-phase biosensors. 

Iwuoha, E., D. de Villaverde, N. Garcia, M.R. Smyth, and J. Pingarron. 1997. Reactivities of organic phase biosensors. 2. The amperometric behavior of horseradish peroxidase immobilised on a platinum electrode modified with an electrosynthetic polyaniline film. Biosens Bioelectron 12 749. 

E. I. Iwuoha, I. Leister, E. Miland, M. R. Smyth, C. O. Fagain, Reactivities of Organic-Phase Biosensors. 1. Enhancement of the Sensitivity and Stability of Amperometric Peroxidase Biosensors Using Chemically Modified Enzymes. Anal. Chem., 69 (1997) 1674-1681. 

Mousty C, Lepellec A, Cosnier S, Novoa A, Marks RS (2001) Fabrication of organic phase biosensors based on multilayered polyphenol oxidase protected by an alginate coating. Electrochem Commun 3 727-732... 

J. Yu and H.X. Ju, Pure organic phase phenol biosensor based on tyrosinase entrapped in a vapor deposited titania sol-gel membrane. Electroanalysis 16, 1305-1310 (2004). 

A. Ciucu, C. Ciucu and R.B. Baldwin, Organic phase potentiometric biosensor for detection of pesticides, Roum. Biotechnol. Lett., 7 (2002) 625-630. 

Hundeck HG, Weifl M, Scheper T, Schubert F (1993) Calorimetric biosensor for the detection and determination of enantiomeric excesses in aqueous and organic phases. Biosens Bioelectron 8 205-208... 

In biocatalytic systems, catalase is mainly used in immobilized state. High activity of immobilized catalase was achieved on its sorption immobilization on cellulose [6], on silica gel modified with fatty acids or phospholipids [7] as well as on activated carbon fibres and brics/tissues/ [8]. Biocatalytic activity of catalase immobilized on cellulose was also studied in nonaqueous solvents [9,10]. In [9] it was found that unlike the enzyme dissolved in water-dimethylformamide medium, on the oxidation of o-dianisidine in the presence of dimethylfonnamide the immobilized catalase does not show any peroxidase activity. It was used [10] for working out an organic-phase amperometric biosensor by immobilizing the enzyme in a polymeric film on a glass-carbon surface. 

Cross-linking an Os-polymer containing 20 PVP (Fig. 11.5) and GOx on a platinum or glassy carbon electrode (GCE) surface with glutaraldehyde, produces biosensors that are very sensitive and stable in organic phases. The CV of the enzyme electrode shows that complexing the polymer with GOx does not change... 

Similar to the behavior of Nafion, poly(ester sulphonic acid) ionomers selectively exclude anionic species and large particles, but cations and neutral molecules are permeable. Of the three Eastman Kodak AQ 29, AQ 38, and AQ 55 polymers, AQ 55 (see the polymer backbone in Fig. 11.12) is the most studied and most applied in biosensor preparation. Wang and coworkers described have features of this polymer as an electrode material, including strong affinity toward hydrophobic counterions, prevention of electrode fouling from proteins, stability of the polymer film on the electrode, ability to preconcentrate catalysts in the film, and lowering the overpotential of many species difficult to oxidize or reduce. Several workers also showed that this poly(ester sulphonic acid) polymer is very stable as an organic phase electrode material. ... 

Utility of nanomaterials depends on the physical properties for the solubility of ultra pure particles in aqueous phase or organic phase retaining the correct stoichiometric ratio. Aqueous phase soluble nanomaterials are used for biological applications as a biosensor and the particle soluble in organic phase is used for electronic applications as shown in Eigure 14.20. The efficiency of nanoparticles depends on the functionalization, which depends on the microstructural properties with phase selections. The successful application of particles depends on the compatible interaction within the particles or between the particle and the substrates for their self-assembly structures with pre-defined geometry at the nanoscale. 

Cristea C, Mousty C, Cosnier S, Popescu IC (2005) Organic phase PPO biosensor based on hydrophilic films of electropolymerized polypyrrole. Electrochim Acta 50 3713-3718... 

HPLC has been shown as an effective method in the fractionation and preparation of AHLs for structural analysis. Preparation of AHL-containing samples for HPLC analysis requires their extraction with organic solvents such as dichloromethane or ethyl acetate [37]. Usually, C8 reverse-phase columns are employed and samples eluted with either gradient or isocratic mobile phases, e.g. acetonitrile-water. Fractions are analysed for the presence of AHLs using the biosensors described in the previous section. AHLs from active fractions can then be identified using more powerful techniques (see following sections). 

Artificial BLMs offer opportunities for development of chemically selective biosensors [6,7], The essential idea is that a receptor (such as a protein molecule) which can selectively bind to a specific organic or biochemical species (stimulant or analyte) can be incorporated into an ordered lipid membrane assembly such that selective binding events between receptor and stimulant will lead to alterations of the phase structure or electrostatic fields of the membrane (transduction). These perturbations can be monitored electrochemically as changes of transmembrane ion conductivity or as alterations in membrane capacitance. 

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