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.

Microbial Biofilms: Features of Formation and Potential for Use in Bioelectrochemical Devices.

Microbial biofilms present one of the most widespread forms of life on Earth. The formation of microbial communities on various surfaces presents a major challenge in a variety of fields, including medicine, the food industry, shipping, etc. At the same time, this process can also be used for the benefit of humans-in bioremediation, wastewater treatment, and various biotechnological processes. The main direction of using electroactive microbial biofilms is their incorporation into the composition of biosensor and biofuel cells This review examines the fundamental knowledge acquired about the structure and formation of biofilms, the properties they have when used in bioelectrochemical devices, and the characteristics of the formation of these structures on different surfaces. Special attention is given to the potential of applying the latest advances in genetic engineering in order to improve the performance of microbial biofilm-based devices and to regulate the processes that take place within them. Finally, we highlight possible ways of dealing with the drawbacks of using biofilms in the creation of highly efficient biosensors and biofuel cells.

Conductive Polymers and Their Nanocomposites: Application Features in Biosensors and Biofuel Cells.

Conductive polymers and their composites are excellent materials for coupling biological materials and electrodes in bioelectrochemical systems. It is assumed that their relevance and introduction to the field of bioelectrochemical devices will only grow due to their tunable conductivity, easy modification, and biocompatibility. This review analyzes the main trends and trends in the development of the methodology for the application of conductive polymers and their use in biosensors and biofuel elements, as well as describes their future prospects. Approaches to the synthesis of such materials and the peculiarities of obtaining their nanocomposites are presented. Special emphasis is placed on the features of the interfaces of such materials with biological objects.

Nanomaterials in bioelectrochemical devices: on applications enhancing their positive effect.

Electrochemical biosensors and biofuel cells are finding an ever-increasing practical application due to several advantages. Biosensors are miniature measuring devices, which can be used for on-the-spot analyses, with small assay times and sample volumes. Biofuel cells have dual benefits of environmental cleanup and electric energy generation. Application of nanomaterials in biosensor and biofuel-cell devices increases their functioning efficiency and expands spheres of use. This review discusses the potential of nanomaterials in improving the basic parameters of bioelectrochemical systems, including the sensitivity increase, detection lower-limit decrease, detection-range change, lifetime increase, substrate-specificity control. In most cases, the consideration of the role of nanomaterials links a certain type of nanomaterial with its effect on the bioelectrochemical device upon the whole. The review aims at assessing the effects of nanomaterials on particular analytical parameters of a biosensor/biofuel-cell bioelectrochemical device.

Microbial Biosensors for Rapid Determination of Biochemical Oxygen Demand: Approaches, Tendencies and Development Prospects.

One of the main indices of the quality of water is the biochemical oxygen demand (BOD). A little over 40 years have passed since the practical application of the first microbial sensor for the determination of BOD, presented by the Japanese professor Isao Karube. This time span has brought new knowledge to and practical developments in the use of a wide range of microbial cells based on BOD biosensors. At present, this field of biotechnology is becoming an independent discipline. The traditional BOD analysis (BOD5) has not changed over many years; it takes no less than 5 days to carry out. Microbial biosensors can be used as an alternative technique for assessing the BOD attract attention because they can reduce hundredfold the time required to measure it. The review examines the experience of the creation and practical application of BOD biosensors accumulated by the international community. Special attention is paid to the use of multiple cell immobilization methods, signal registration techniques, mediators and cell consortia contained in the bioreceptor. We consider the use of nanomaterials in the modification of analytical devices developed for BOD evaluation and discuss the prospects of developing new practically important biosensor models.

Modification of thermally expanded graphite and its effect on the properties of the amperometric biosensor.

The work considered the properties of a biosensor based on a novel nanomaterial-modified thermally expanded graphite (TEGM). The main focus was on whether the procedure of additional graphite thermal expansion would affect the electrochemical properties of biosensors based on membrane fractions of acetic acid bacteria Gluconobacter oxydans. Raman spectroscopy, scanning electron microscopy and electrochemical analysis were used for the study. Raman spectra showed that the formation of TEGM led to its stratification into smaller particles and a better orderly layered structure with high "graphenization" degree. Modification of TEG led to the formation of additional cavities into which bacterial cells or bacterial membrane fractions could be immobilized and affect the electrical conductivity of the biosensors positively. Calculation of the heterogeneous charge transfer constants showed that processes occurring on the electrodes are quasi-reversible. The limiting stage of these processes is the transfer of an electron from a biological component on the electrode surface, not the diffusion of the analyte from the solution to the active centers of the enzyme. We showed the possibility of developing third-generation mediator-free biosensors for glucose detection based on TEGM, as well as of second-generation mediator biosensors for glucose, ethanol and glycerol detection.

The Use of Diethoxydimethylsilane as the Basis of a Hybrid Organosilicon Material for the Production of Biosensitive Membranes for Sensory Devices.

Biomembranes based on an organosilica sol-gel matrix were used to immobilize bacteria Paracoccus yeei VKM B-3302 as part of a biochemical oxygen demand (BOD) biosensor. Diethoxydimethylsilane (DEDMS) and tetraethoxysilane (TEOS) were used as precursors to create the matrix in a 1:1 volume ratio. The use of scanning electron microscopy (SEM) and the low-temperature nitrogen adsorption method (BET) showed that the sol-gel matrix forms a capsule around microorganisms that does not prevent the exchange of substrates and waste products of bacteria to the cells. The use of DEDMS as part of the matrix made it possible to increase the sensitivity coefficient of the biosensor for determining BOD by two orders of magnitude compared to a biosensor based on methyltriethoxysilane (MTES). Additionally, the long-term stability of the bioreceptor increased to 68 days. The use of such a matrix neutralized the effect of heavy metal ions on the microorganisms' catalytic activity in the biosensor. The developed biosensor was used to analyze water samples from water sources in the Tula region (Russia).

Gluconobacter Oxydans-Based MFC with PEDOT:PSS/Graphene/Nafion Bioanode for Wastewater Treatment.

Microbial fuel cells (MFCs) are a variety of bioelectrocatalytic devices that utilize the metabolism of microorganisms to generate electric energy from organic matter. This study investigates the possibility of using a novel PEDOT:PSS/graphene/Nafion composite in combination with acetic acid bacteria Gluconobacter oxydans to create a pure culture MFC capable of effective municipal wastewater treatment. The developed MFC was shown to maintain its activity for at least three weeks. The level of COD in municipal wastewater treatment was reduced by 32%; the generated power was up to 81 mW/m2 with a Coulomb efficiency of 40%. Combining the MFC with a DC/DC boost converter increased the voltage generated by two series-connected MFCs from 0.55 mV to 3.2 V. A maximum efficiency was achieved on day 8 of MFC operation and was maintained for a week; capacitors of 6800 µF capacity were fully charged in ~7 min. Thus, G. oxydans cells can become an important part of microbial consortia in MFCs used for treatment of wastewaters with reduced pH.

Nanotechnology-based promising strategies for the management of COVID-19: current development and constraints.

INTRODUCTION: COVID-19 pandemic has been declared as a global emergency by the World Health Organization which has mounted global pressure on the healthcare system. The design and development of rapid tests for the precise and early detection of infection are urgently needed to detect the disease and also for bulk screening of infected persons. The traditional drugs moderately control the symptoms, but so far, no specific drug has been discovered. The prime concern is to device novel tools for rapid and precise diagnosis, drug delivery, and effective therapies for coronavirus. In this context, nanotechnology offers novel ways to fight against COVID-19. AREA COVERED: This review includes the use of nanomaterials for the control of COVID-19. The tools for diagnosis of coronavirus, nano-based vaccines, and nanoparticles as a drug delivery system for the treatment of virus infection have been discussed. The toxicity issues related to nanoparticles have also been addressed. EXPERT OPINION: The research on nanotechnology-based diagnosis, drug delivery, and antiviral therapies is at a preliminary stage. The antiviral nanomedicine therapies are cost-effective and with high quality. Nanoparticles are a promising tool for prevention, diagnosis, antiviral drug delivery, and therapeutics, which may open up new avenues in the treatment of COVID-19.

Use of PEDOT:PSS/Graphene/Nafion Composite in Biosensors Based on Acetic Acid Bacteria.

Immobilization of the biocomponent is one of the most important stages in the development of microbial biosensors. In this study, we examined the electrochemical properties of a novel PEDOT:PSS/graphene/Nafion composite used to immobilize Gluconobacter oxydans bacterial cells on the surface of a graphite screen-printed electrode. Bioelectrode responses to glucose in the presence of a redox mediator 2,6-dichlorophenolindophenol were studied. The presence of graphene in the composite reduced the negative effect of PEDOT:PSS on cells and improved its conductivity. The use of Nafion enabled maintaining the activity of acetic acid bacteria at the original level for 120 days. The sensitivity of the bioelectrode based on G. oxydans/PEDOT:PSS/graphene/Nafion composite was shown to be 22 µA × mM-1 × cm-2 within the linear range of glucose concentrations. The developed composite can be used both in designing bioelectrochemical microbial devices and in biotechnology productions for long-term immobilization of microorganisms.

Direct Bioelectrocatalytic Oxidation of Glucose by Gluconobacter oxydans Membrane Fractions in PEDOT:PSS/TEG-Modified Biosensors.

Recent years have witnessed an ever-increasing interest in developing electrochemical biosensors based on direct electron transfer-type bioelectrocatalysis. This work investigates the bioelectrocatalytic oxidation of glucose by membrane fractions of Gluconobacter oxydans cells on screen-printed electrodes modified with thermally expanded graphite and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS). Electrooxidation of glucose was shown to occur without the presence of electron transport mediators. Chronoamperometric and cyclic voltametric characteristics showed an increase of anodic currents at electrode potentials of 0-500 mV relative to the reference electrode (Ag/AgCl). The direct electron transfer effect was observed for non-modified PEDOT:PSS as well as for PEDOT:PSS linked with crosslinkers and conductive fillers such as polyethylene glycol diglycidyl or dimethyl sulfoxide. Bioelectrodes with this composite can be successfully used in fast reagent-free glucose biosensors.

Electrochemical assessment of the interaction of microbial living cells and carbon nanomaterials.

This work considers the effects of various carbon nanomaterials and fibres on bioelectrocatalytic and respiratory activity of bacterial cells during the oxidation of ethanol in the presence of an electron transport mediator. Gluconobacter oxydans sbsp. industrius VKM B-1280 cells were immobilised on the surfaces of graphite electrodes and had an adsorption contact with a nanomaterial (multi-walled carbon nanotubes, thermally expanded graphite, highly oriented pyrolytic graphite, graphene oxide, reduced graphene oxide). The electrochemical parameters of the electrodes (the polarisation curves, the value of generated current at the introduction of substrate, the impedance characteristics) were measured in two-electrode configuration. Modification by multi-walled carbon nanotubes led to the increase of microbial fuel cell (MFC) electric power by 26%. The charge transfer resistance of modified electrodes was 47% lower than unmodified ones. Thermally expanded and pyrolytic graphites had a slight negative effect on the electrochemical properties of modified electrodes. The respiratory activity of bacterial cells did not change in the presence of nanomaterials. The data can be used in the development of microbial biosensors and MFC electrodes based on Gluconobacter cells.

Multiwalled Carbon Nanotubes and the Electrocatalytic Activity of Gluconobacter oxydans as the Basis of a Biosensor.

This paper considers the effect of multiwalled carbon nanotubes (MWCNTs) on the parameters of Gluconobacter oxydans microbial biosensors. MWCNTs were shown not to affect the structural integrity of microbial cells and their respiratory activity. The positive results from using MWCNTs were due to a decrease in the impedance of the electrode. The total impedance of the system decreased significantly, from 9000 kOhm (G. oxydans/chitosan composite) to 600 kOhm (G. oxydans/MWCNTs/chitosan). Modification of the amperometric biosensor with nanotubes led to an increase in the maximal signal from 65 to 869 nA for glucose and from 181 to 1048 nA for ethanol. The biosensor sensitivity also increased 4- and 5-fold, respectively, for each of the substrates. However, the addition of MWCNTs reduced the affinity of respiratory chain enzymes to their substrates (both sugars and alcohols). Moreover, the minimal detection limits were not reduced despite a sensitivity increase. The use of MWCNTs thus improved only some microbial biosensor parameters.

Comparative Study of Electrochemical Sensors Based on Enzyme Immobilized into Polyelectrolyte Microcapsules and into Chitosan Gel.

The characteristics of an electrochemical biosensor based on a Prussian-blue screen-printed electrode containing glucose oxidase incorporated into polyelectrolyte microcapsules (PMC) are considered. PMC with the embedded enzyme were formed using sodium polystyrene sulfonate and poly(allylamine hydrochloride). The characteristics were compared with those of the enzyme immobilized in chitosan gel. We assessed the dependences of biosensor signals on the composition of the buffer solution, on the glucose concentration; the operational and long-term stabilities. The enzyme immobilized in PMC proved to be more sensitive to buffer molarity at a maximum within 35 - 40 mM. The apparent Michaelis constants were 1.5 and 4.1 mM at the immobilization in, respectively, chitosan and PMC. The developed biosensors were used to assay commercial juices. The biosensors' data on the glucose contents were shown to have a high correlation with the standard spectrophotometric assay (0.92 - 0.95%), which implies a possible application of the fabricated biosensors in foodstuff analysis.

Bioelectrochemical Properties of Enzyme-Containing Multilayer Polyelectrolyte Microcapsules Modified with Multiwalled Carbon Nanotubes.

This work investigated changes in the biochemical parameters of multilayer membrane structures, emerging at their modification with multiwalled carbon nanotubes (MWCNTs). The structures were represented by polyelectrolyte microcapsules (PMCs) containing glucose oxidase (GOx). PMCs were made using sodium polystyrene sulfonate (polyanion) and poly(allylamine hydrochloride) (polycation). Three compositions were considered: with MWCNTs incorporated between polyelectrolyte layers; with MWCNTs inserted into the hollow of the microcapsule; and with MWCNTs incorporated simultaneously into the hollow and between polyelectrolyte layers. The impedance spectra showed modifications using MWCNTs to cause a significant decrease in the PMC active resistance from 2560 to 25 kOhm. The cyclic current-voltage curves featured a current rise at modifications of multilayer MWCNT structures. A PMC-based composition was the basis of a receptor element of an amperometric biosensor. The sensitivity of glucose detection by the biosensor was 0.30 and 0.05 µA/mM for PMCs/MWCNTs/GOx and PMCs/GOx compositions, respectively. The biosensor was insensitive to the presence of ethanol or citric acid in the sample. Polyelectrolyte microcapsules based on a multilayer membrane incorporating the enzyme and MWCNTs can be efficient in developing biosensors and microbial fuel cells.

Effects of Polymer Matrices and Carbon Nanotubes on the Generation of Electric Energy in a Microbial Fuel Cell.

The anode of a microbial fuel cell (MFC) was formed on a graphite electrode and immobilized Gluconobacter oxydans VKM-1280 bacterial cells. Immobilization was performed in chitosan, poly(vinyl alcohol) or N-vinylpyrrolidone-modified poly(vinyl alcohol). Ethanol was used as substrate. The anode was modified using multiwalled carbon nanotubes. The aim of the modification was to create a conductive network between cell lipid membranes, containing exposed pyrroloquinoline quinone (PQQ)-dependent alcoholdehydrogenases, and the electrode to facilitate electron transfer in the system. The bioelectrochemical characteristics of modified anodes at various cell/polymer ratios were assessed via current density, power density, polarization curves and impedance spectres. Microbial fuel cells based on chitosan at a matrix/cell volume ratio of 5:1 produced maximal power characteristics of the system (8.3 µW/cm²) at a minimal resistance (1111 Ohm cm²). Modification of the anode by multiwalled carbon nanotubes (MWCNT) led to a slight decrease of internal resistance (down to 1078 Ohm cm²) and to an increase of generated power density up to 10.6 µW/cm². We explored the possibility of accumulating electric energy from an MFC on a 6800-µF capacitor via a boost converter. Generated voltage was increased from 0.3 V up to 3.2 V. Accumulated energy was used to power a Clark-type biosensor and a Bluetooth transmitter with three sensors, a miniature electric motor and a light-emitting diode.