M. E. Khlupova

Biocatalytic synthesis of conducting polymers and prospects for its application

Enzymatic methods of synthesis of conducting polymers, physicochemical properties of the resulting products, and mechanisms of the reactions are considered. The enzymes involved in oxidative polymerization of monomers are briefly characterized. Examples of practical application of enzymatically synthesized conducting polymers are given.

Intact and permeabilized cells of the yeast Hansenula polymorpha as bioselective elements for amperometric assay of formaldehyde

Intact and permeabilized yeast cells were tested as the biorecognition elements for amperometric assay of formaldehyde (FA). For this aim, the mutant C-105 (gcr1 catX) of the methylotrophic yeast Hansenula polymorpha with a high activity of AOX was chosen. Different approaches were used for monitoring FA-dependent cell response including analysis of their oxygen consumption rate by the use of a Clark electrode, as well as assay of oxidation of redox mediator at a screen-printed platinum electrode covered by cells entrapped in Ca-alginate gel. It was shown that oxygen consumption rate of permeabilized cells reached its saturation at 4mM of FA (23 degrees C). The detection limit was found to be 0.27mM. In the presence of redox mediator 2,6-dichlorophenolindophenol (DCIP), the screen-printed platinum band electrode covered by permeabilized cells did not show any current output to FA. In contrast, well-pronounced amperometric response to FA was observed in the case of intact yeast cells in the presence of DCIP. It was shown that current output reached its maximum at 7mM concentration of FA. The detection limit was found to be 0.74mM. Obviously, it is necessary to perform a directed genetic engineering of the yeast cells to improve their bioanalytical characteristics in the corresponding biosensors.

Laccase-catalyzed synthesis of aniline oligomers and their application for the protection of copper against corrosion

A new method for the enzymatic synthesis of oligoaniline soluble in organic solutions is developed. The high-redox potential laccase from the fungus Trametes hirsuta is used as a biocatalyst and atmospheric oxygen serves as oxidant. Aniline oligomers showed a high inhibition of copper corrosion in aqueous HCl and NaCl solutions.

Enzymatic polymerization of dihydroquercetin using bilirubin oxidase

Dihydroquercetin (or taxifolin) is one of the most famous flavonoids and is abundant in Siberian larch (Larix sibirica). The oxidative polymerization of dihydroquercetin (DHQ) using bilirubin oxidase as a biocatalyst was investigated and some physicochemical properties of the products were studied. DHQ oligomers (oligoDHQ) with molecular mass of 2800 and polydispersity of 8.6 were obtained by enzymatic reaction under optimal conditions. The oligomers appeared to be soluble in dimethylsulfoxide, dimethylformamide, and methanol. UV-visible spectra of oligoDHQ in dimethylsulfoxide indicated the presence of highly conjugated bonds. The synthesized oligoDHQ was also characterized by FTIR and 1H and 13C NMR spectroscopy. Comparison of NMR spectra of oligoDHQ with DHQ monomer and the parent flavonoids revealed irregular structure of a polymer formed via the enzymatic oxidation of DHQ followed by nonselective radical polymerization. As compared with the monomer, oligoDHQ demonstrated higher thermal stability and high antioxidant activity.

Aniline Polymerization on Multiwall Carbon Nanotubes with Immobilized Laccase

A composite material consisting of electrically conductive polyaniline deposited on the surface of multiwall carbon nanotubes has been synthesized. Enzymatic synthesis was carried out in the presence of Trametes hirsuta laccase immobilized on the nanotube surface. The obtained composite was morphologically uniform, and its electrochemical capacity and stability were much higher than those of a composite synthesized according to the conventional chemical procedure.

Enhanced performance of a flexible supercapacitor due to a combination of the pseudocapacitances of both a PANI/MWCNT composite electrode and a gel polymer redox electrolyte

In this paper, a combination of the pseudocapacitances of both an enzymatically synthesized polyaniline/multi-walled carbon nanotube (PANI/MWCNT) composite with a core shell structure and a gel polymer redox electrolyte was used to improve the specific characteristics of a supercapacitor (SC). The gel of polyvinyl alcohol in sulfuric acid containing sodium 1,2-naphthoquinone-4-sulfonate (PVA/H2SO4/NQS) was used as a gel polymer redox electrolyte. Electrochemical studies have shown that the redox behavior of NQS is a diffusion-controlled and quasi-reversible process. The PANI/MWCNT composite in 13 mM NQS solution had a high specific capacitance of ca. 1100 F g−1 at a scan rate of 5 mV s−1 (three electrode cell configuration). The symmetrical flexible SC device based on the PANI/MWCNT composite and the PVA/NQS gel redox electrolyte had a power density of 1.8 kW kg−1 and an energy density of 23.3 W h kg−1. After 3000 cycles of potential scanning, the specific capacitance of the SC device decreased by less than 7%.

Biocatalytic approach as alternative to chemical synthesis of polyaniline/carbon nanotube composite with enhanced electrochemical properties

A new approach is proposed to biocatalytical synthesis of a thin homogeneous layer of conducting polyaniline (PANI) on the surface of MWCNTs using the laccase Trametes hirsuta. Aniline dimer, an enhancer of laccase-catalyzed aniline polymerization, has been adsorbed on MWCNTs. Phytic acid has been used as acidic dopant and gelator. The PANI/MWCNT composite has a core shell structure and shows a high specific capacitance of 554 F g−1 and long-term cycling stability. The approach enables the production of nanostructured composite conducting hydrogel.

Laccase-Catalyzed Heterocoupling of Dihydroquercetin and p-Aminobenzoic Acid: Effect of the Reaction Product on Cultured Cells

Derivatization of the natural flavonoid dihydroquercetin with p-aminobenzoic acid was carried out in an ethyl acetate/citric buffer biphasic system using laccase from the fungus Trametes hirsuta. The main reaction product yield was ~68 mol %. The product was characterized by 1H NMR, 13C NMR, and liquid chromatography-mass spectroscopy, and its structure was elucidated. The reaction product affected viability of cultured human rhabdomyosarcoma cells (RD cell line) in a dose-dependent manner and, therefore, can be of interest to pharmaceutical industry.

Dihydroquercetin polymerization using laccase immobilized into an ionic liquid

It was shown that the laccase (LC) included into hydrophobic ionic liquid (IL) can be reused for the biotransformation of dihydroquercetin (DHQ). The physicochemical characteristics of DHQ oligomers synthesized using LC/IL did not differ from the characteristics of the oligomers obtained with native laccase. The synthesized oligomers have a number average molecular weight of 1050 g/mol and a polydispersity index of 1.41. Oligomers possess higher antioxidant activity than the monomer.