Amperometric biosensor based on denatured DNA for the study of heavy metals complexing with DNA and their determination in biological, water and food samples

Amperometric biosensor (BS) has been elaborated based on the stationary mercury-film electrode (SMFE) with silver support and cellulose nitrate (CN) membrane containing immobilized single-stranded DNA (ssIDNA). The sorption isotherms and ssDNA-heavy metal binding constants have been obtained with the BS. According to these data, the chosen heavy metals form the following series of binding strength with ssIDNA: Pb(II)>Fe(III)>Cd(II). It has been found that upon the competitive adsorption, there exists practically simultaneous sorption of different ions at ssIDNA containing membrane. The method of the determination of heavy metals based on preconcentration of metal ions on the BS followed by the destruction of DNA-metal complexes with ethylenediamine tetraacetate (EDTA) and voltammogram recording has been proposed. The lower limits of detectable contents are 1.0×10-10, 1.0×10 -9 and 1.0×10-7 mol l-1 for Pb(II), Cd(II) and Fe(III), respectively. Heavy metals have been assayed in natural and drinking water, milk and blood serum samples even under simultaneous presence with a selectivity factor of 1:10. The effect of matrix components has been estimated. © 2004 Elsevier B.V. All rights reserved

Determination of pharmaceuticals based on indole alkaloids with amperometric DNA-sensors and enzyme immunoassay test-system

Bioaffine methods were developed for determining indole-containing alkaloids ajmaline and vincristine. These methods are based on the proposed amperometric DNA-sensors and on immunoenzyme test-system with a spectrophotometric indication of the analytical signal. The complexing between ajmaline and immobilized native DNA (n-IDNA) allows effective preliminary concentration from test solutions on the biosensor. The time of analysis is 25-30 min, limit of detection (LOD) for ajmaline is 1.0×10-10 M. The test-system utilized the immunological reaction of ajmaline with its antibodies and the enzyme marker, horseradish peroxidase, LOD is 1.5×10-9 M. Anti-cancer vincristine interaction with immobilized renatured DNA (r-IDNA) was studied and determination was carried out using an amperometric DNA-sensor. Bioaffine membrane drug concentration and reactivation of the sensor was performed. The affinity binding constant Kbind for vincristine-r-IDNA complex calculated by Scatchard's method was found to be high enough [(5.0±0.4)×105 ll mol] confirming high specificity of the complexing with r-IDNA. The duration of the assay is 40 min. The developed method is characterized with an LOD of 1.1×10-9 M, with the lack of the need for long sample processing. The pharmaceuticals were determined by those methods in model solutions of blood serum and in tablets and solutions for injections. © Taylor & Francis Group, LLC

Extraction polarography and its analytical applications

The review is devoted to extraction polarography as a method for the determination of microelements. The possibilities of polarography in combination with a preliminary chemical separation of the elements by extraction are discussed. The types of extraction-polarographic systems known at present are described. It is shown that the selectivity of extraction separations increases if the reagents form complexes with the ions to be determined, which are manifested by effects on the polarisation curves at different potentials. The influence of extracting and ionising solvents on the analytical signal is examined from the standpoint of modern ideas of the chemistry of coordination compounds in non-aqueous media. Examples of the use of extraction polarography for the determination of microelements are presented. © 1980 IOP Publishing Ltd

Suppression of activity of Candida Albicans proteinases by cobalt chloride

Influence of cobalt (II) chloride on the system of Candida albicans proteinase (SAP C. alb.) (both in solution and immobilized on a surface of nitrocellulose membranes) has been investigated. In solution cobalt chloride inactivated inducible but not constitute enzyme. In the heterogenous sytem proteolitical effect of the cobalt ion on inductible proteinase was also observed

Bioaffine methods for determining ajmaline using an amperometric DNA-sensor and an immunoenzyme spectrophotometric test system

Bioaffine methods are developed for determining indole-containing alkaloid ajmaline, which has a cytostatic effect and is used as a cardiac drug. These methods are based on the proposed amperometric DNA-sensor and on immunoenzyme test system with the spectrophotometric indication of the analytical signal. The complex formation between ajmaline and immobilized native DNA allows ajmaline to be efficiently preconcentrated on the biosensor from test solutions. Optimum conditions for preconcentrating ajmaline and those for reactivating the biosensor for its repeated use are found. The time of analysis is 25-30 min, the determination limit for ajmaline is 3.0 × 10-10 M (RSD = 33%). In the test system, the immunological reaction of ajmaline with its antibodies and the enzyme marker, horseradish peroxidase, are used. The determination limit is 4.0 × 10-9 M (RSD = 33%). Ajmaline is determined by the two methods in model solutions of blood serum and in tablets and solutions for injections. © 2009 Pleiades Publishing, Ltd

Electrochemical properties of metal complexes of dithio-acid derivatives and their application in extraction polarography

Metal complexes with dithiocarbamic (dtc), xanthic (xan) and dithiophosphoric (dtp) acids give rise to one or more polarographic waves in dimethylformamide and in mixtures of extracting solvents and ethanol. The electrons are found to be transferred stepwise in the case of unfilled d-shell metal complexes. The shift of half-wave potential depends on the ligand, increasing in the order dtp < xan < dtc. In solvents with low solvation power the electrode processes are more reversible. The linear dependence of the limiting current on the chelate concentration has been used for determining the metal in the organic phase without re-extraction. Pb(II), Bi(III) and As(III) have been separated with dtp as extractant, and the concentrations of Co(II), Ni(II) and Zn(II) complexes (simultaneously extracted) have been determined polarographically. © 1978

Amperometric DNA biosensor for the determination of auto-antibodies using DNA interaction with Pt(II) complex

A method of denatured DNA immobilisation on cellulose nitrate film has been developed. A modified film of uniform and stable surface has been used as a bio-sensitive part of amperometric DNA biosensor based on the stationary mercury-film covered silver electrode. The biosensor has been used to devise a new variant of solid-phase immunoassay of auto-antibodies (Ab) in blood serum without separation of components. The content of auto-Ab was monitored by measuring the currents of catalytic hydrogen evolution (with potentials of -1.2 and -1.4V) resulting from the complexing of Pt(II) with DNA or auto-Ab respectively. The determination has been performed within a wide concentration area of 5.0×10-10 to 7.0×10-8M. The limit of detection is 3.0×10-10M. The affinity constants for the immunoreaction of DNA-antibodies have been found to be 1.25×10 9 and 2.50×108M-1, which confirms the specificity of the interaction. The protocol of the immunoassay has been proposed and the procedure of diagnosing Aleutian mink disease (AMD) has been described here. © 2003 Elsevier B.V. All rights reserved

Detection of DNA autoantibodies using a novel amperometric biosensor on the basis of platinum(II) complex with DNA | Opredelenie autoantitel k DNK s pomoshch'iu novogo amperometricheskogo biosensora na osnove kompleksa platiny(II) s DNK.

A biochemical biosensor was developed on the basis of a steady-state Hg-film electrode and either DNA molecules or antibodies to DNA immobilized in a cellulose nitrate film. This biosensor is designed to measure the concentration of DNA (or antibodies to DNA), and it can be used in the diagnosis of autoimmune diseases. Electric current of catalytic H2 evolution caused by complexing between DNA (antibodies to DNA) and Pt(II) was used as an analytical signal. The detection sensitivity threshold for DNA and antibodies to DNA was 10 and 0.075 microgram/ml, respectively

Electrochemical reduction of bifunctional organic compounds Communication 5. Kinetics of the rearrangement of endiols in the reduction of paradiacetylbenzene and terephthalic aldehyde

1. The kinetics of the rearrangement of endiols to a monocarbonyl compound in the reduction of p-diacetylbenzene and terephthalic aldehyde was studied. 2. The equilibrium constants of the preceding reaction of hydration of terephthalic aldehyde was measured. © 1972 Consultants Bureau, a division of Plenum Publishing Corporation

Stripping-voltammetric determination of some amino acids on a carbon-paste electrode modified by crown ethers

A method for detecting sulfur-containing amino acids on a carbon-paste electrode modified by dibenzo-18-crown-6 or dibromodibenzo-18-crown-6 ethers is developed. The selectivity of the method is accounted for by a specific interaction between crown ethers (modifying agents) and protonated amino groups of organic molecules of the analyte adsorbed by the surface of the modified electrode as a host-guest complex. The determination limits (clim) of cysteine, homocysteine, and glutathione are equal to (2-5) x 10-8 M. © 1997 MAEe Cyrillic signK Hayκa/Interperiodica Publishing