P.V. Rodionov

Properties and analytical applications of the self-assembled complex {peroxidase-chitosan}.

A novel promising approach to the improvement of analytical properties of horseradish peroxidase based on its inclusion into self-assembled structures of chitosan is discussed. It is shown that the reasonable choice of a polyelectrolyte, a detailed investigation of its interaction with the enzyme and the conditions of the {peroxidase-polyelectrolyte} complex formation allow for stabilizing the biocatalyst in aqueous and aqueous-organic media without a substantial loss in its activity and developing corresponding analytical procedures and biosensors. The latter provides highly selective determination of a number of organic compounds and sensitive determination of heavy metal ions that becomes possible due to the specific interactions of the analytes with the polymer matrix. Besides, the application of the proposed analytical systems and biosensors provides the expansion of the range of the compounds, and poorly water soluble and slowly oxidized substrates of peroxidase as well, which could be determined and real samples which could be analyzed by enzymatic methods. Analytical performance of the developed spectrophotometric indicator procedures and biosensors based on the self-assembled complex {peroxidase-chitosan} is demonstrated in the determination of metal ions (Hg(II), Cd(II), and Pb(II)), phenothiazines (promazine, chloropromazine, and trifluoroperazine), phenolic compounds (phenol, hydroquinone, catechol, pyrogallol, quercetin, rutin, and esculetin), organic peroxides (tert-butyl peroxide, 2-butanone peroxide, and benzoyl peroxide) in various samples, including water-insoluble matrices.

A solid-phase fluorescent biosensor for the determination of phenolic compounds and peroxides in samples with complex matrices

A solid-phase fluorescent biosensor for the determination of phenolic compounds (simple substituted phenols and catecholamines) and peroxides has been developed. The biosensor has a simple construction and the analytical signal is measured directly in a biosensitive layer {peroxidase-chitosan} on the sensor surface. This approach allowed analyzing samples with complex matrices (including water-insoluble samples and nontransparent solutions) without their preliminary pretreatment. Two novel fluorescent indicator reactions for the determination of the above-mentioned analytes in wide concentration ranges (from nmol l−1 to mm l−1) which provided an analytical signal registration on a solid phase were proposed. The developed sensor was applied successfully for the analysis of urine, cosmetics, pharmaceuticals preparations, etc.

Determination of hydrogen peroxide and organic peroxides in micellar and aqueous–organic media using a spectrophotometric biosensor based on horseradish peroxidase

The expedience of the target-specific control of the properties of a medium (using micellar and aqueous–organic media), in which an indicator process providing the background for the operation of a spectrophotometric sensor based on a polyelectrolyte complex (horseradish peroxidase–chitosan) is conducted, is shown experimentally and proved by calculations of kinetic parameters of the enzymatic reaction. The application of the sensor ensures an increase in the sensitivity of the determination of peroxides of different nature and structures (e.g., hydrogen and urea peroxides, benzoyl peroxide, 2-butanone peroxide and tertbutyl hydroperoxide) in complex matrixes. The proposed approach allows the analyst not only to regulate the performance characteristics of the developed procedures for the determination of peroxides depending on the analytical task, but also to extend the range of test samples (including those insoluble in water) analyzed with no sample preparation.

Approaches to increasing the sensitivity of the determination of phenolic compounds using chitosan-based solid-phase optical biosensors

It was shown that the sensitivity of the determination of phenolic compounds using chitosan-based optical biosensors could be increased by varying the sorption conditions of products of enzymatic oxidation of phenolic compounds. Sorption isotherms of oxidation products of phenolic compounds by a chitosan film were studied according to Langmuir and Freundlich models. Quantitative characteristics of the sortpion process, such as maximum sorption capacity, the Langmuir isotherm constants, and the Gibbs free energy were determined.

Optical sensors for determining phenolic compounds with different structures

The literature data published in 1993–2012 on the development and application of optical sensors for the determination of phenolic compounds of various structures are summarized. The design, analytical characteristics, and advantages and disadvantages of the existing optical sensors are reviewed, and some examples of using optical sensors in the analysis of real samples, including those from field experiments, are considered in detail.