Novel Conductive Polymer Composite PEDOT:PSS/Bovine Serum Albumin for Microbial Bioelectrochemical Devices

A novel conductive composite based on PEDOT:PSS, BSA, and Nafion for effective immobilization of acetic acid bacteria on graphite electrodes as part of biosensors and microbial fuel cells has been proposed. It is shown that individual components in the composite do not have a significant negative effect on the catalytic activity of microorganisms during prolonged contact. The values of heterogeneous electron transport constants in the presence of two types of water-soluble mediators were calculated. The use of the composite as part of a microbial biosensor resulted in an electrode operating for more than 140 days. Additional modification of carbon electrodes with nanomaterial allowed to increase the sensitivity to glucose from 1.48 to 2.81 μA × mM-1 × cm-2 without affecting the affinity of bacterial enzyme complexes to the substrate. Cells in the presented composite, as part of a microbial fuel cell based on electrodes from thermally expanded graphite, retained the ability to generate electricity for more than 120 days using glucose solution as well as vegetable extract solutions as carbon sources. The obtained data expand the understanding of the composition of possible matrices for the immobilization of Gluconobacter bacteria and may be useful in the development of biosensors and biofuel cells.

Vitamin B6-based fluorescence chemosensor for selective detection of F- ions: design, synthesis, and characterization

The present paper reports on the synthesis and characterization of a new chemosensor for fluoride ions, a hydrazone derived from pyridoxal 5'-phosphate and benzothiazole. The structure of the chemosensor was confirmed using 1H and 13C NMR, FT-IR and mass spectroscopy. The conformational diversity of the chemosensor influencing the sensor activity was studied by the quantum chemistry methods on the B3LYP/6-311++G(d, p) (H, C, N, O, P, S) level, and the optimal structure of the chemosensor was chosen. The selective capability of detecting F- in the aqueous solution, which also contains Cl-, Br-, I-, NCS-, ClO4-, HSO4-, and NO3- was demonstrated. The detection limit (LOD) for fluoride ions was 0.22 µM as determined by the 3σ method. The turn-on effect in the presence of fluoride ions is based on the deprotonation of the chemosensor and its subsequent aggregation in DMSO. In addition, the chemosensor was used for the detection and estimation of F- in real samples using fluorescence spectroscopy.

A Two-Mediator System Based on a Nanocomposite of Redox-Active Polymer Poly(thionine) and SWCNT as an Effective Electron Carrier for Eukaryotic Microorganisms in Biosensor Analyzers

Electropolymerized thionine was used as a redox-active polymer to create a two-mediated microbial biosensor for determining biochemical oxygen demand (BOD). The electrochemical characteristics of the conducting system were studied by cyclic voltammetry and electrochemical impedance spectroscopy. It has been shown that the most promising in terms of the rate of interaction with the yeast B. adeninivorans is the system based on poly(thionine), single-walled carbon nanotubes (SWCNT), and neutral red (kint = 0.071 dm3/(g·s)). The biosensor based on this system is characterized by high sensitivity (the lower limit of determined BOD concentrations is 0.4 mgO2/dm3). Sample analysis by means of the developed analytical system showed that the results of the standard dilution method and those using the biosensor differed insignificantly. Thus, for the first time, the fundamental possibility of effectively using nanocomposite materials based on SWCNT and the redox-active polymer poly(thionine) as one of the components of two-mediator systems for electron transfer from yeast microorganisms to the electrode has been shown. It opens up prospects for creating stable and highly sensitive electrochemical systems based on eukaryotes.

[Properties of streptokinase included in polyetylenglycol microcapsules]

Thrombolytic therapy by high doses of streptokinase (SK) that are stipulated by its rapid clearance is accompanied by side effects. In this work for the purpose of lifetime prolongation in bloodstream and decrease in side effects SK was included in microcapsules from water-soluble polyethyleneglygol (PEG) using the double emulsification method. By variation of the emulsification conditions, molecular weight of PEG (20 or 40 kDa) and PEG/SK ratio (12 or 8 mg PEG/1000 IU SK) it was obtained four preparations of PEG-microcapsules with high percent of SK inclusion (approximately 90-91%), which has completely preserved its fibrinolytic activity and released from microcapsules with different rates. The time of SK full release from obtained PEG-microcapsules was varied from 45 to 90 min (pH 7.4; 37 degrees C). The comparative in vitro study ofthrombolytic and side effects of free SK and SK*PEG-microcapsules was conducted. It was found that at equal doses (500 IU/mL) the lysis rates of human plasma clots under the action of encapsulated preparations of SK (with the exception of a small lag period) were equal to the lysis rate induced by free SK. Besides, SK*PEG-microcapsules caused a less exhaustion of plasminogen and fibrinogen in plasma than free SK.