Electrochemical biosensors based on dendrimers

© 2015, Pleiades Publishing, Ltd. The main features of work of electrochemical biosensors including dendrimers of various structures in the biosensing layer are considered. The role and importance of dendrimers as matrixes for the immobilization of biological components of biosensors and an increase in the density of receptors and mediators of electron transfer are revealed. Examples of application of various types of biosensors based on enzymes, immunochemical reagents, and nucleic acids are presented

Molecular receptors and electrochemical sensors based on functionalized calixarenes

The approaches to the design of molecular receptors based on functionalized calixarenes aimed at recogni- tion of ions and neutral organic compounds are considered; such receptors can serve as the basis for potentiometric and amperometric sensors. The application of the receptors is exemplified and analytical characteristics of the sensors are discussed. Particular attention is paid to the factors affect- ing the efficiency of recognition and selectivity and sensi- tivity of the developed sensors. The bibliography includes 173 references. © 2010 Russian Academy of Sciences and Turpion Ltd

Effect of metal ions on the colorimetric determination of irreversible cholinesterase inhibitors

Colorimetric tests based on cholinesterase preparations stabilized by N-phthalylchitosan were developed. They determine organophosphorus irreversible inhibitors in the concentration range n × 10-8-n × 10-7 M (Diazinon, Zolone, Carbophos, Co-ral, and Metaphos) or n × 10-7-n × 10-5 M (DDVP) with the use of an AKI-Ts-01 analyzer. Test characteristics depend on the nature of the substrate (butyrylcholine iodide or indophenyl acetate) and on the presence of reversible effectors (copper and aluminum salts), which impair the inhibiting effect of organophosphorus compounds. N-Phthalylchitosan affects the sensitivity of cholinesterase to reversible and irreversible inhibitors. This effect may be associated with the formation of stabilizer-metal or stabilizer-enzyme-metal complexes. © 1997 MAEe cyrillic signK Hayκa/Interperiodica Publishing

The Application of Cholinesterase Potentiometric Biosensor for Preliminary Screening of the Toxicity of Waste Waters

The application of cholinesterase biosensor for preliminary testing of total pollution of domestic and industrial discharges has been investigated. The results indicate that biosensor-based testing is more sensitive than paramecia bioassay. For numerous samples tested, the inhibition degree of biosensor response exceeds the appropriate value of acute toxicity on Paramecium caudatum. Electrochemical oxidation of the samples, before the biosensor testing readily removes oxidizable compounds which do not effect a real risk of environmental pollution. Simultaneous determination of inhibitory effect, acute toxicity and biochemical (chemical) oxygen demand makes it possible to infer a possible source of contamination of waters

Electrochemical sample preparation for the enzymatic determination of cholinesterase inhibitors

An electrochemical sample preparation procedure for the enzymatic determination of thione organophosphorus pesticides has been examined. This procedure is based on the galvanostatic electrolysis of thione pesticides in the presence of chlorides or bromides, in which the pesticides are oxidized to oxygen analogs. The efficiency of sample preparation depends on the halogen nature. The kinetic studies have shown that, in the case of bromides, the subsequent determination with a native enzyme (colorimetric detection) is complicated by the mixed character of inhibition. The presence of a reversible component is caused by the presence of the residual unoxidized pesticide. With the use of cholinesterase immobilized on paper (a potentiometric biosensor), only the effect of an irreversible inhibitor (the major product of electrochemical pesticide oxidation) is observed, regardless of the nature of the oxidants generated. © 1997 MAEe cyrillic signK Hayκa/Interperiodica Publishing

A cholinesterase sensor based on a graphite electrode modified with 1,3-disubstituted calixarenes

New cholinesterase sensors based on screen-printed graphite and graphite/epoxy electrodes modified with 1,3-disubstituted calix[4]arenes were developed for the detection of compounds that form host-guest complexes (using copper(II) and oxalate ions as an example). The effect of calix[4]arenes on the biosensor signal was studied under homogeneous and heterogeneous conditions. It was found that the effect of the studied compounds was due to changes in the electrostatic interactions and mobility of enzyme effectors in the electrode layer. Procedures were developed for the determination of Cu(II) by its activating effect in the concentration range 0.05-4.0 mM and of oxalate ions by their inhibiting effect in the concentration range 0.5-20 mM

Detection of aptamer-protein interactions using QCM and electrochemical indicator methods

Electrochemical indicator methylene blue and differential pulse voltammetry allowing to determine charge transfer from electrode surface to the thrombin bounded on a DNA aptamer and thus to detect thrombin (1) with high selectivity in comparison with nonspecific binding caused by human IgG (2) or human serum albumin (HSA) (3). We report novel method of detection thrombin-aptamer interaction based on measurement the charge consumption from the electrode covered by DNA aptamers to an electrochemical indicator methylene blue (MB), that is bounded to a thrombin. The binding of thrombin to an aptamers has been detected also by QCM method in flow measuring cell. We showed that using MB it is possible to detect thrombin with high sensitivity and selectivity. © 2004 Elsevier Ltd. All rights reserved

Solid-Contact Potentiometric Sensor Based on Polyaniline and Unsubstituted Pillar[5]Arene

© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. A novel potentiometric sensor based on screen-printed carbon electrode covered with electropolymerized polyaniline (PANI) and unsubstituted pillar[5]arene as ionophore has been developed and tested in potentiometric measurements of pH and metal ions. The introduction of pillar[5]arene improved the reversibility of the pH response in the range from 2.0 to 9.0 with the slope of 45mV/pH. Among metal cations, the response to Fe3+ and Ag+ ions was referred to PANI redox conversion whereas the signal toward Cu2+ in the range from 1.0×10-6 to 1.0×10-2M (limit of detection (LOD) 3.0×10-7M) to specific interaction with the macrocycle

Choline esterase inhibitors and synthetic oxalic acid receptors based on calix[4]arene derivatives

New reversible butyrylcholine esterase inhibitors based on calix[4]arene derivatives were suggested. A series of new distally disubstituted calix[4]arenes were prepared in 60-80% yields. Some of these compounds showed properties of reversible choline esterase effectors, activating it at low concentrations and inhibiting at high concentrations. The macrocycles prepared were tested in extraction of d,l-tartaric, glycolic, d,l-mandelic, d,l-glutamic, malonic, oxalic, and succinic acids and of sodium acetate. Oxalic acid is efficiently transferred through a liquid impregnated membrane under the action of calix[4]arenes with nitrogen-containing substituents. ©2005 Pleiades Publishing, Inc

Affinity biosensors based on disposable screen-printed electrodes modified with DNA

Simple and sensitive DNA sensors have been developed on a base on graphite screen-printed electrodes modified with DNA and enzymes. Cholinesterase and peroxidase immobilized by treatment with glutaraldehyde were used for the detection of human DNA antibodies of systemic lupus erythematosus and bronchial asthma patients. The amperometric signal was measured at +680mV versus Ag/AgCl for DNA-cholinesterase sensor and -150mV for DNA-peroxidase sensor 5min after the injection of acethylthiocholine and hydroquinone, respectively. The addition of serum samples results in the sharp decrease of the signal due to the formation of DNA-antibody adducts followed by the suppression of the access of substrate to the enzyme active site. Sulfonamide medicines suppress the DNA-antibody interaction due to the competitive binding along DNA minor grooves. DNA sensor labeled with peroxidase showed the linear calibration range of 5×10-9 to 7×10-5moll-1 of sulfamethoxazole and of 5×10-8 to 1×10-4moll-1 of sulfathiazole. © 2002 Elsevier Science B.V. All rights reserved