[en] One of the objectives during designing of enzymatic biofuel cells is to avoid using of electron mediators - substances, which mediate electron transfer between the electrode surface and the active centers of enzymes. During this configuration it is not necessary to separate the cathodic and anodic space by membrane, what facilitates the transport of protons from the anode to the cathode while allowing miniaturization of the entire facility effectively. This work presents a biofuel cell based on direct electron transfer of fructose dehydrogenase and bilirubin oxidase immobilized on an electrode modified by gold nanoparticles. The device showed a maximum power of 27.4 mW · cm^-2 at 0.3 V and the value of the potential (without flowing current) 746 mV. Then for this cell an increase of the maximum performance during operation in a reduced volume of electrolyte was detected in accordance with the expected facilitated metabolism and cartridge diffusion. (authors)

[en] Escherichia coli 2260 cells bound to solid carriers (iodo-and bromoacetyl cellulose) were incubated in the Davis mineral medium and changes in respiratory activity, ATP level, ¹⁴C-valine and ¹⁴C-adenine incorporation and the number of bacteria able to multiply were investigated. As compared with suspended cells, no significant changes in the rate and capacity of the metabolic processes studied were recorded. Iodoacetyl cellulose had the smallest effect on the rates of nucleic acids and protein syntheses. (author). 3 figs., 2 tabs., 11 refs

[en] A mixture of heterotrophic bacteria and collection strains of Escherichia coli and Pseudomonas fluorescens were immobilized in calcium alginate or pectate gels. A comparison of respiratory activity, substrate uptake and biosynthetic capacity of immobilized cells showed that both types of carriers permitted a prolonged preservation of metabolic activity but the transfer of substances through the gel was faster in the pectate. Morphological changes included some intracellular structures, partial shrinkage of the plasma membrane of immobilized cells, and transformation of a rod-like cell shape to an oval one. (author). 5 figs., 2 tabs., 19 refs

[en] Glycans and other saccharide moieties attached to proteins and lipids, or present on the surface of a cell, are actively involved in numerous physiological or pathological processes. Their structural flexibility (that is based on the formation of various kinds of linkages between saccharides) is making glycans superb 'identity cards'. In fact, glycans can form more 'words' or 'codes' (i. e., unique sequences) from the same number of 'letters' (building blocks) than DNA or proteins. Glycans are physicochemically similar and it is not a trivial task to identify their sequence, or-even more challenging-to link a given glycan to a particular physiological or pathological process. Lectins can recognise differences in glycan compositions even in their bound state and therefore are most useful tools in the task to decipher the 'glycocode'. Thus, lectin-based biosensors working in a label-free mode can effectively complement the current weaponry of analytical tools in glycomics. This review gives an introduction into the area of glycomics and then focuses on the design, analytical performance, and practical utility of lectin-based electrochemical label-free biosensors for the detection of isolated glycoproteins or intact cells. (author)

[en] The aim of the work was preparation of thin layers of graphene oxide (GO) electrodes from low-viscosity aqueous GO dispersions by rotary coating and subsequent reduction of prepared GO electrodes by low-temperature diffuse coplanar surface barrier discharge plasma (DCSBD) in hydrogen atmosphere. The positive effect of reducing plasma in rGO electrodes resulted in a decrease in the quantitative representation of oxygen bonds and at the same time a decrease in their electrical surface resistance. (authors)

[en] Nanocrystalline powders and ceramics with controlled grain size from 15 to 3000 nm of PbMg_1/3Nb_2/3O₃(PMN) and (PMN)_0.65-(PbTiO₃)_0.35 (PMN-PT35) have been synthesized using the ball milling method. Dielectric experiments have revealed in PMN a disappearance of relaxation below ≅30 nm grain size and combined x-ray and Raman experiments the vanishing of correlations between polar nanoregions (PNRs). A similar study in morphotropic compound PMN-PT35 has shown the appearance of a relaxor state below ≅200 nm, associated to a destruction of the ferroelectric domains state towards PNRs in a paraelectric matrix. These phenomena are discussed in connection with pressure experiments from the literature and on the basis of polar states destabilization by both elastic and electric random fields changes associated with the size reduction

[en] We describe the preparation and characterization of a glassy carbon electrode modified with a bionanocomposite consisting of a hyaluronic acid, dispersed carbon nanotubes, and electrostatically bound toluidine blue. The electrode was used to detect NADH in the batch and flow-injection mode of operation. The electrode was further modified by immobilizing sorbitol dehydrogenase to result in biosensor for D-sorbitol that displays good operational stability, a sensitivity of 10.6 μA mM^-1 cm^-2, a response time of 16 s, and detection limit in the low micromolar range. The biosensor was successfully applied to off-line monitoring of D-sorbitol during its bioconversion into L-sorbose (a precursor in the synthesis of vitamin C) by Gluconobacter oxydans. The sample assay precision is 2.5% (an average RSD) and the throughput is 65 h^-1 if operated in the flow-injection mode. The validation of this biosensor against a reference HPLC method resulted in a slope of correlation of 1.021 ± 0.001 (R² = 0.99997). (author)

[en] An 85 nm-thick morphotropic PbZr_0.52Ti_0.48O₃ (PZT) film grown epitaxially and [001]-oriented onto a SrTiO₃-buffered Si-wafer is investigated using temperature dependent X-ray diffraction. Two phase transitions, at T_rt ∼ 500 K and T_c ∼ 685 K, are evidenced and are attributed to structural phase transitions from monoclinic-like to tetragonal-like phase and from tetragonal to paraelectric phase, respectively. The stronger upper shift of T_rt value with respect to the bulk one and the weakly affected T_c (T_c bulk ∼ 665 K) are explained assuming misfit strain changes when crossing T_rt. This finding opens new perspectives for piezoelectric PZT films in harsh applications.

[en] The β phase stability in poly(vinylidene fluoride/trifluoroethylene) [P(VDF-TrFE)] thin films was studied below 300 K using X-ray diffraction and polarization-electric-field (P-E) hysteresis loops measurements. On as-grown samples, an irreversible partial order-disorder transformation at T_β ∼ 250 K, namely, the β relaxation temperature, was evidenced by the appearance of an additional X-Ray diffraction peak above T_β as well as changes on the P-E loops on heating after the first cooling. This order-disorder-like transformation which is attributed to an all-trans order to helical disorder transition is suggested to take place in defect-rich regions like crystal-amorphous interphases and/or crystalline areas with randomly distributed TrFE defect-like units