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The bioelectrochemical and spectral properties of immobilized Gluconacetobacter sucrofermentas VKPM B-11267 bacteria were studied in the presence and absence of multiwalled carbon nanotubes (MWCNTs). The obtained characteristics were compared with the characteristics of Gluconobacter oxydans, which are phylogenetically close to them and are widely used in bioelectrochemistry. It was shown that modification of the bioelectrode with carbon nanotubes leads to a significant increase in the current level (by 2.5–3 times), as well as to a decrease in the total resistance both in the absence of substrates and in their presence. The potential use of immobilized G. sucrofermentas cells as part of a microbial fuel cell (MFC) was considered. The specific electrical power of an MFC based on immobilized G. sucrofermentas cells was lower than that of an MFC based on G. oxydans cells. Nevertheless, the results obtained indicate that G. sucrofermentas VKPM B-11267 cells can serve as a biocatalyst in MFCs.

A new approach has been developed for the formation of the biosensor recognition elements via the immobilization of microorganisms in layer-by-layer films in order to determine the biochemical oxygen demand (BOD). Bioreceptor elements of BOD-biosensors have been fabricated based on the bacterial microorganisms Paracoccus yeei, Pseudomonas veronii, and Bacillus proteolyticus isolated from activated sludge. The recognition element was formed with via layer-by-layer deposition; each layer contained cells of one species. A similar multilayered recognition element based on yeast cells of Ogataea angusta, Blastobotrys adeninivorans, and Debaryomyces hansenii was created. In both cases, the cells were immobilized in a hydrogel of polyvinyl alcohol modified with N-vinylpyrrolidone. It was found that layer-by-layer immobilization increases the sensitivity of both the yeast- and bacterial cell–based biosensors. It was surmised that this is due to the lack of competition for substrate within the layer and its greater ability to each of the cell layers. The effects of the composition of the assayed samples (pH, ionic strength, heavy metal compounds) on the oxidative activity of the developed recognition elements have been studied. The analytical and metrological characteristics of the biosensors have been defined. The lower limit of the estimated BOD5 values was 0.5 mg О2/dm3 and 0.7 mg О2/dm3 for bacterial- and yeast cell–based biosensors, respectively. BOD5 was detected in water samples with the fabricated recognition elements. It was shown that the use of these two bioreceptors makes it possible to obtain data that strongly agree with those obtained with traditional method and that biosensing analyzers can act as prototype pilot model of the devices

This review deals with the use of the highly conductive polymer PEDOT:PSS in biomedical and bioelectrochemical systems. The examples of toxic effects on living cells, positive effects of PEDOT:PSS on the viability of cells and tissues are given. The properties of the polymer, methods of increasing its electrical conductivity by its modification with various nanoparticles and nanomaterials are discussed. Examples of using PEDOT and its composites in bioelectrochemical devices, such as biosensors and biofuel cells, are considered. Changes in the characteristics of biosensors and biofuel cells under the influence of PEDOT are discussed.

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.

We used conducting redox-active polymers based on chitosan and bovine serum albumin (BSA), covalently bound to mediators ferrocene or Neutral Red, or thionine, modified by carbon nanotubes, as a base of an amperometric biosensor for determining glucose. The structure of the obtained polymers was studied by IR spectroscopy and scanning electron microscopy. Their electrochemical characteristics were studied by cyclic voltammetry. The redox-active polymer based on BSA covalently bound to ferrocene and modified by carboxylated carbon nanotubes demonstrated the most promising characteristics. The biosensor based on the selected hybrid polymer is characterized by high sensitivity, a lower limit of determined concentrations of 0.05 mM, and a high correlation coefficient (R = 0.9919) with the results of determination of glucose in human blood by an alternative method.

A study is made of the effect the aperture and the number of electrode pairs of an interdigital transducer (IDT) have on the characteristics of acoustic signals A1 and SH1 excited in a LiNbO3YX-plate. The obtained dependences of signal intensity on the experimental parameters demonstrate the possibility of miniaturizing integrated sensors consisting of a array of sensors based on delay lines or single IDT resonators.

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.

The Gluconacetobacter sucrofermentas bacterial cells are immobilized in a chitosan gel on the surface of an electrode obtained by matrix printing. The nature of the change in the bioelectrochemical parameters of the immobilized bacteria under the influence of multiwalled carbon nanotubes (MWCNTs) are studied. We studied the electrochemical signals of cells upon the introduction of substrates (glucose, ethanol) by three methods: chronoamperometry, cyclic voltammetry, and impedance spectroscopy. The introduction of ethyl alcohol at a concentration of 1 mM leads to a decrease in the total resistance of the electrode by a factor of ~40. Modification of the electrode using MWCNTs leads to an increase in the current (by factors of 8 to 10) and an additional decrease in the total electrode resistance by a factor of ~10. These effects are similar to the effects of substrates and MWCNTs on the phylogenetically related Gluconobacter oxydans cells. The formation of bacterial cellulose (BC) membrane cells during the growth does not fundamentally change the effects of the substrates and MWCNTs.

In this review, we consider the trend in the development of biosensors (BSs) that manifests itself in the transition from macro- to micro- and nanodevices. In the successful interaction of biochemical/biotechnological and microelectronic technologies, the use of nanomaterials is accelerating this process. A similar trend is taking place in the development of biofuel elements. Despite the fact that the BS’s dimensions are not subject to accurate quantitative assessment and are not of paramount importance, it is important to pay attention to them when planning the practical application of analytical equipment. The most effective examples are used to illustrate the reduction in the physical size of BSs since their creation in the early 1960s to the present day.

Along with traditional methods for the determination of environmental pollution, biosensors have become widely used in recent years. The review surveys modern microbial biosensors for determining pesticide residues in the environment. A microbial biosensor is a complex analytical device in which a microorganism is a sensitive element that responds to the presence of a pesticide in the test sample and the analytical signal depends on the concentration of the compound to be determined. The basic principles of the formation of these biosensors and their advantages and disadvantages are described. Methods of the immobilization of microorganisms as the constituents of a biosensor and various types of signal transducers are presented. The future prospects for this line of inquiry are considered.

The creation of implantable devices that support the functioning of the body is an important area in the field of medical technology. Many of these devices require a power supply, and it is desirable that such sources work during the entire period of implantation, even in the case of a lifelong implant installation. The published data on energy sources for powering implantable and wearable medical devices is reviewed. A comparative assessment of the characteristics of biofuel cells as the most developed version of an implantable energy source with other renewable sources of electric energy based on thermo-, piezo-, electrostatic (ES), magneto-, and photo-converters is given. Particular attention is paid to the use of implantable devices that can serve as a source of energy for low-power systems: micropumps, pacemakers, neuroimplants, etc.

The characteristics of biosensors based on screen-printed electrodes containing glucose oxidase, alcohol oxidase, lactate oxidase, and a mixture of glucose oxidase and γ-amylase are studied. The enzymes have been immobilized in a conductive hydrogel of cross-linked bovine serum albumin modified with carbon nanotubes. The developed biosensors are applicable for the quantification of glucose, ethanol, lactic acid, and starch in fermentation media. The analytical and metrological characteristics of these biosensors are determined. The developed biosensor system allows for quantification of glucose, ethanol, lactate, and starch in the concentration range of 0.1–2.7, 1–27, 0.02–73 mM, and 0.6–21 g/L, respectively. Samples of alcoholic and fermented milk products, kvass, and fermentation mass have been analyzed. Statistical analysis of the assay results shows that glucose, ethanol, lactic acid, and starch concentrations determined by biosensors insignificantly differ from those determined by the reference methods. The developed set of biosensors based on specifically selected enzymes can be used for effective monitoring of biotechnological processes as an alternative to the conventional analytical methods.

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.

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.

By their geometric dimensions, biosensors can be arranged into a sequence of macro-, micro- and nanodevices. From this perspective, the present chapter considers mainly electrochemical biosensors and biofuel cells; attention is also paid to other, e.g. chemical, types of sensors that can be prototypes of developed biosensor devices. One of the moving forces of miniaturization is finding conditions when the least amount of material is used. Miniature devices can play the role of biosensors and represent electrodes for biofuel systems. Due to the broad use of the enzyme glucose oxidase (GOD), which acts as a model protein or the base of existing devices, we discuss in detail the planar technology of forming a multichannel nanobiochip based on the immobilized GOD. The prospects of micro/nanostructures are primarily determined by their miniature size, the feasibility of easy duplication and—in production—a combined application of molecular electronics technology and biochemical methods of manipulations with biological material.

A novel, simple and ‘green’ electrochemical exfoliation method was used to prepare a graphene (GR) dispersion. The as-obtained GR was characterized using HR-TEM, which confirmed the exfoliation of a few layers of graphene from graphite sheets. Furthermore, the GR film was coated on a glassy carbon electrode (GCE) surface via drop-casting. Then, electro-polymerization was carried out using the GR-modified electrode in acetonitrile solution (ACN) containing 10 μM 3,4-ethylenedioxythiophene (EDOT) and 100 mM lithium perchlorate (LiClO4). The electro-polymerized PEDOT (poly(3,4-ethylenedioxythiophene)) on the GR film-modified electrode was analyzed using FE-SEM and Raman spectroscopy, which confirmed the successful incorporation of PEDOT on the GR surface. The electrochemical characterization of PEDOT/GR/GCE was carried out by electrochemical impedance spectroscopy (EIS) in 0.1 M KCl containing 5 mM [Fe(CN)6]3−/4−. The electrochemical measurements revealed that our proposed PEDOT/GR film exhibited a high active surface area, redox currents and high charge transfer rate (Ks). Under optimized conditions, PEDOT/GR/GCE showed a higher oxidation peak current for nicotine at +0.91 V (vs. Ag/AgCl) in 0.1 M phosphate buffer solution (PBS; pH 7). Furthermore, PEDOT/GR/GCE responded linearly for nicotine detection from 0.5 to 1000 μM with a limit of detection at 47 nM. The selectivity and sensitivity of the electrochemical sensor (PEDOT/GR/GCE) were determined in the presence of important interfering molecules. In addition, the stability and reproducibility of the PEDOT/GR/GCE sensor were tested. Finally, the PEDOT/GR-based sensor was successfully applied to detect nicotine in tobacco samples with high accuracy.

Self-powered biosensors use the principle of a; an assayed substance in them also serves as the source of electric energy required for the device to operate. This makes it possible to simplify the design and avoid using external power supply sources. Self-powered biosensors were developed for medical analysis of compounds such as lactate, ethanol, glucose, thrombin, acetylcholine, and others. These devices can find wide application not only in medicine but also in fields like ecological monitoring. This will solve several tasks simultaneously: the cleanup of the environment, assessment of the number of contaminants, and generation of electric energy. This chapter considers the recent achievements in the field of autonomous power-supply biosensors and their advantages/drawbacks as compared with other types of biosensors.

Biosensors became one of the promising technologies in recent years. Wide applications and active development of related technologies lead to rising number of biosensors-related publications. A lot of them focused on the implantable biosensors that can help to operate future implantable medical devices. One of the main issues for implantable biosensors became power supply. In this chapter, several perspective approaches for the development of self-power biosensors are discussed. We have presented an overview of power generation approaches that can be applied in the case of implantable biosensors applications. It is worth mentioning that bioelectrochemical systems can be very powerful, but their influence on the organism is still not fully clear. Also, an overview of recent research in the field of electroconductive materials for implantable bioelectrochemical systems, with both biofuel cells and biosensors application, is presented. Moreover, a variety of approaches for material development from carbon nanomaterials to the polymeric systems have been described; and finally, some novel approaches for self-powered implantable systems are discussed.

Blood glucose analysis is currently an important issue both for ordinary people wishing to monitor their health and for patients suffering from various diseases, especially diabetes mellitus. This chapter considers nano- and microsized devices based on biological receptors for glucose level measurements. As attention is largely paid to non-invasive techniques, we also touch upon the existing glucose assays for other fluids of the organism that require no skin-cover integrity to be disturbed. We present data on the development of continuous blood glucose level monitoring to provide a true picture of glycemic changes over large periods of time. The advantages and limitations of using enzyme electrochemical biosensors for glucose detection are discussed. A part of the work deals with specific features of using carbon and metal nanoparticles in biosensors to improve their properties. The current fundamental research in the development of biosensors and available commercial devices is also discussed.

Flexible energy storage devices have received great interest due to the increasing demand for wearable and flexible electronic devices with high-power energy sources. Herein, a novel hybrid flexible hexagonal boron nitride integrated graphene paper (BN/GrP) is fabricated from 2D hexagonal boron nitride (h-BN) nanosheets integrated with graphene sheets dispersion via a simple vacuum filtration method. FE-SEM indicated that layered graphene nanosheets tightly confined with h-BN nanosheets. Further, the Raman spectroscopy confirmed successful integration of BN with graphene. As-prepared BN/GrP free-standing flexible conductive paper showed high electrical conductivity of 5.36 × 104 S m−1 with the sheet resistance of 8.87 Ω sq−1. However, after 1000 continuous bending cycles, the BN/GrP sheet resistance increased just about 8.7% which indicated good flexibility of the paper. Furthermore, as-prepared BN/GrP showed excellent specific capacitance of 321.95 F g−1 at current density of 0.5 A g−1. In addition, the power and energy densities were obtained as 3588.3 W kg−1, and 44.7 W h kg−1, respectively. The stability of the prepared flexible electrode was tested in galvanostatic charge/discharge cycles, where the results showed the 96.3% retention even after 6000 cycles. These results exhibited that the proposed BN/GrP may be useful to prepare flexible energy-storage systems.

This work proposes a method of forming a microorganism–mediator(s) receptor system, in which the rates of separate stages of mediator bioelectrocatalysis are used as the basis for the development of biosensors for the biochemical oxygen demand (BOD) rapid assay. In the presence of a ferrocene mediator, the yeast Blastobotrys adeninivorans was shown to enable oxidation of a larger range of substrates as compared with other investigated microorganisms—bacteria Escherichia coli and yeast Ogataea polymorpha. The rate constants of the interaction of the yeast B. adeninivorans with nine compounds, electron transfer mediators, were determined; the best mediator for these microorganisms was found to be neutral red (k(int) = 0.681 ± 0.009 dm(3)/g s). Neutral red possesses a high rate of interaction with the ferrocene mediator (14,200 ± 100 dm(3)/mol s) shown earlier to be the most promising acceptor of electrons at a carbon paste electrode (0.4 ± 0.1 cm/s). These features enabled the formation of a two-mediator ferrocene–neutral red system to be used in a biosensor. A two-mediator-based biosensor had a higher sensitivity (the lower limit of detected BOD concentrations, 0.16 mg/dm(3)) than that of a one-mediator system based on neutral red and ferrocene. Analysis of ten samples from surface water reservoirs showed the combination of ferrocene, neutral red and the yeast B. adeninivorans to enable the data that highly correlated (R = 0.9693) with those of the standard method.

This work investigated the use of redox-active polymers based on bovine serum albumin and chitosan, covalently bound to mediators neutral red and ferrocene and containing carbon nanotubes, for immobilization of Paracoccus yeei VKM B-3302 bacteria. The structures of produced polymers were studied by IR spectroscopy and scanning electron microscopy. Cyclic voltammetry and impedance spectroscopy found the electrochemical characteristics of the investigated systems: the heterogeneous electron transfer rate constant, the constant of the rate of interaction with P. yeei bacteria and the impedance. The systems containing carbon nanotubes and ferrocene-based redox-active polymer proved to be the most promising. Biosensors formed using the hybrid polymers had a high sensitivity with the lower boundary of 0.1 mg/dm3 of the detected BOD5 concentrations and a high correlation (R = 0.9916) with the standard BOD assay of surface water samples.

Three bacterial strains (SPB1, SPB2, and SPB3) isolated from the activated sludge of treatment facilities most efficiently oxidized (as compared to other strains) a model solution based on glucose and glutamic acid in the presence of a ferrocene mediator. The possible use of isolated strains as a basis for a mediator-type amperometric BOD biosensor was studied. Analysis of 16S rRNA genes demonstrated that the SPB1, SPB2, and SPB3 strains are 99.79–100% similar to the Paracoccus yeei BAA-599T, Pseudomonas veronii DSM 11331T, and Bacillus proteolyticus TD42T strains, respectively. It was established that the bioreceptor element based on the P. yeei SPB1 strain possessed the best characteristics. It was stable in storage at 4°С for 22 days, and the lower limit of detectable concentrations was 1.3 mg О2/dm3. In order to search for the most efficient electron transfer mediator for this strain, nine compounds, including ferrocene, thionine, methylene blue, potassium hexacyanoferrate(III), and 2,6-dichlorophenolindophenol, were screened. The mediator electron transfer signals were obtained for each of them. Ferrocene was the most efficient in terms of sensitivity and the amount of substrate oxidation that can be registered in the presence of the mediator. An analysis of ten samples of wastewater (before and after purification) and the rivers of Tula oblast demonstrated that the use of ferrocene and P. yeei SPB1 strain cells made it possible to obtain data with a high correlation (R = 0.9934) with the results of the standard method.

This work investigated the properties of Paracoccus yeei VKM B-3302 bacteria isolated from activated sludge and immobilized in an N-vinylpyrrolidone-modified poly(vinyl alcohol) matrix. The developed hydrogel formed a network structure to enable the entrapment of microbial cells with their viability and biocatalytic properties preserved, which ensured the technological possibility of replicating expendable biosensor receptor elements. A new ratio of the components for the synthesis selected in this work enabled producing a copolymer of an earlier undescribed chemical structure, which can be efficiently used for immobilization of highly sensitive P. yeei bacteria. A biological oxygen demand (BOD) biosensor with these bacteria and matrix was shown to possess a long-time stability exceeding that described earlier, to have a broad substrate specificity and to exceed approximately tenfold the nearest analogues by its sensitivity and the lower boundary value of 0.05 mg/dm(3). The biosensor enabled assays of water samples initially attributed to pure samples (the BOD range, 0.05–5.0 mg/dm(3)). BOD assays of water samples from various sources showed the use of the receptor element of this composition to enable the data that closely correlated with the standard method (R(2) = 0.9990).

Electropolymerized neutral red, thionine, and aniline were used as part of hybrid nanocomposite conductive polymers, to create an amperometric reagent-less biosensor for glucose determination. The structure of the obtained polymers was studied using infrared (IR) spectroscopy and scanning electron microscopy. Electrochemical characteristics were studied by cyclic voltammetry and impedance spectroscopy. It was shown that, from the point of view of both the rate of electron transfer to the electrode, and the rate of interaction with the active center of glucose oxidase (GOx), the most promising is a new nanocomposite based on poly(neutral red) (pNR) and thermally expanded graphite (TEG). The sensor based on the created nanocomposite material is characterized by a sensitivity of 1000 ± 200 nA × dm3/mmol; the lower limit of the determined glucose concentrations is 0.006 mmol/L. The glucose biosensor based on this nanocomposite was characterized by a high correlation (R2 = 0.9828) with the results of determining the glucose content in human blood using the standard method. Statistical analysis did not reveal any deviations of the results obtained using this biosensor and the reference method. Therefore, the developed biosensor can be used as an alternative to the standard analysis method and as a prototype for creating sensitive and accurate glucometers, as well as biosensors to assess other metabolites.

The anode of a microbial fuel cell was used to determine the index of biochemical oxygen demand. The fuel cell was developed with an activated graphite electrode modified with polyvinyl alcohol containing N-vinylpyrrolidone. The combination of polyvinyl alcohol with N-vinylpyrrolidone was used to immobilize Gluconobacter oxydans bacteria. The application of this matrix made it possible to obtain a microbial fuel cell possessing a high sensitivity and a minimal time for a single measurement of the BOD5 index, which were 8.3 mV dm3/mg O2 and 30 min, respectively. The lower limit of the determined values of biochemical oxygen demand was 0.34 mg O2/dm3. The determination of the wastewater BOD5 indicated that these results agreed with the data of the standard method (the correlation coefficient was 0.99). The studied biosensor model exceeded the described analogs in such characteristics as the lower limit of detection and the minimal time for a single measurement.

This work deals with the creation of an enzyme biosensor based on electrochemical impedance spectroscopy (EIS) and the possibility of applying EIS in the quantitative determination of glucose using the screen-printed electrodes modified by glucose oxidase.

Four types of carbon fiber materials (CFMs) obtained by electrospinning polyacrylonitrile solutions are considered. The CFMs intertwine with cells of Gluconobacter oxydans or with their membrane fractions (MFs). Bioelectrochemical characteristics of the electrodes (chrono- and voltamperometric, as well as impedance spectra) are studied. Electrodes are considered a model of the anode of the microbial biofuel cell (MFC). Ethyl alcohol is the oxidized substrate. MALDI-TOF MS demonstrates that MFs retain the protein structure of whole cells and therefore can be used as analogues of whole cells. It is shown that the MFC based on carbon fiber material obtained after 30-min treatment at 1000°C has the highest power and stability. When MFs are used as a biocatalyst, nonmediated charge transfer is observed for all studied CFMs. These results can be successfully used for the design of biosensors and MFCs.

The modification of an electrode produced by a matrix printing head with the use of glucose oxidase (GOD), single-walled carbon nanotubes (SWCNTs), and thermoexpanded graphite (TEG) has been studied. During glucose oxidation, modification by SWCNTs leads to the effect of direct electron transfer. Both nanomaterials increase the magnitude of the sensitivity coefficient (SC) from 0.11 to 0.24 mA M–1 in the case of glucose oxidase–and ferrocene-based electrodes when modification is done with the addition of TEG and up to 0.62 mA M–1 when modification is done with the addition of SWCNTs. A comparison of the characteristics of the biosensors with ferrocene and nanomaterials with those of the mediator-free biosensors based on SWCNTs and GOD shows that the biosensor provides higher sensitivity detection; the magnitude of sensitivity coefficient is 1.5 mA M–1. The higher magnitude of the SC can be explained by the occurrence of more effective electron transfer from active centers of the enzyme to the electrode. Voltammetric measurements demonstrate that electron transfer in a mediator-free biosensor is not complicated by a chemical reaction and is carried out under the control of diffusion factors. After testing the mediator-free biosensor in practice, it is possible to talk about the applicability of such a biosensor in detecting glucose in different environments, including the fermentation industry.

The effects of stress factors (drying, low temperature, and long-term storage) on the survival of the actinobacteria Gordonia polyisoprenivorans 135, which is used as a biosensor receptor to detect sodium benzoate in water solutions, were studied, as well as the effects of these factors on the biodegradation of aromatic compounds. The cells remained viable after starvation and subsequent long-term storage in suspension. Immobilization of G. polyisoprenivorans 135 cells prevented the loss of the viability when they were dried prior to storage. The immobilized cells, which were used as a biosensor receptor element, were active in relation to benzoate for more than 9 months. Storage of the receptor at 4°C for four months led to a sensor response to 10–4 and 10–3 M benzoate at a level of 69 and 79% of the maximum, respectively, while the response was 58 and 51% (70 pA/s and 140 pAs), respectively, after 9 months of storage. These results suggest that actinobacterial cells can survive an adverse environment and can be used to create highly stable and sensitive bioreceptors.

The mediators ferrocene, 1,1'-dimethylferrocene, ferrocene carboxaldehyde, ferrocene acetonitrile, neutral red, 2,6-dichlorophenolindophenol, thionine, methyl blue, and potassium ferricyanide were used in combination with Debaryomyces hansenii yeast cells to create a biosensor receptor for biochemical oxygen demand (BOD) assays. In this eukaryote, ferrocene and neutral red were observed to efficiently transfer electrons. The biosensor based on ferrocene was characterized by long-term stability (39 days) and a wide range of substrate specificity. The lower detected concentration boundary was 25.2 mg O2/dm3. A high correlation (R = 0.9971) was observed between the results obtained with water samples by this approach and the standard method. This is the first attempt to create a combination of yeast cells and a mediator. The biosensor can be employed for further research on the possibilities of its conventional use.

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.

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.

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.

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&ndash, 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 &mu, A/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.

The maximal rates and effective constants of 2,6-dichlorphenolindophenol and oxygen reduction by bacterim Gluconobacter oxydans in bacterial fuel cells under different conditions were evaluated. In an open-circuit mode, the rate of 2,6-dichlorphenolindophenol reduction coupled with ethanol oxidation under oxygen and nirogen atmospheres were 1.0 and 1.1 μM s–1 g–1, respectively. In closed-circuit mode, these values were 0.4 and 0.44 μM s–1 g–1, respectively. The initial rate of mediator reduction with the use of membrane fractions of bacteria in oxygen and nitrogen atmospheres in open-circuit mode were 6.3 and 6.9 μM s–1 g–1, whereas these values in closed-circuit mode comprised 2.2 and 2.4 μM s–1 g–1, respectively. The oxygen reduction rates in the presence and absence of 2,6-dichlorphenolindophenol were 0.31 and 0.32 μM s–1 g–1, respectively. The data obtained in this work demonstrated independent electron transfer from bacterial redox centers to the mediator and the absence of competition between the redox mediator and oxygen. The results can make it possible to reduce costs of microbial fuel cells based on activity of acetic acid bacteria G. oxydans.

The effect of carbon nanomaterials (carbon nanotubes, thermally expanded and pyrolytic graphite) on the bioelectrochemical activity of Gluconobacter oxydans bacterial cells was studied during sorption contact with nanomaterials. For bacterial immobilization, the surface of a working bioelectrode was modified via the application of bacterial suspension in the studied nanomaterial and chitosan. The bioelectrochemical electrode characteristics (the amplitude of generated potential, cyclic volt–ampere characteristics, resistance) were estimated before and in the process of bacterial interaction with ethanol (3-electrode measurement scheme). Modification of the spectral graphite electrode by carbon nanotubes allowed a decrease in the resistance of the charge transfer by 48% and an increase in the oxidation current on cyclic volt—ampere characteristics at a voltage of 200 mV by 21% as compared with nonmodified electrode. The thermally expanded and pyrolytic graphite increased the bioelectrode resistance to 4050 and 8447 Ohm cm2, respectively. Mathematical modeling demonstrated that from 75 to 100% of biomaterial (depending on the used nanomaterial) were involved in the process of electricity generation with the selected method of the bacterial immobilization. The use of data obtained during the development of microbial biosensors and electrodes of biofuel cells is discussed.

We have studied the properties of a bioelectrode formed by the immobilization of Gluconobacter oxydans bacterial cells on carbon superfine materials (CSMs). We use three types of CSMs (as adopted by the working classification CSM 1–3) with different carbonization rates. The bioelectrode is formed by covering the surface of the CSM suspension of bacteria in a chitosan gel. The properties of samples are evaluated by measuring the physiological state of the bacteria immobilized: (a) recording the intensity of cellular respiration, (b) for measuring the charge transport characteristics of electrode (bioelectrocatalysis), and (c) by measuring the electrode impedance. Measurements (b) and (c) are made on two and three-electrode circuits in the oxidation of ethanol in the presence of 2,6-dichlorophenol bacteria electron transport mediator. For CSMs 1 and 2 the electron transport by the oxidation of the substrate is not registered, while for CSM 3 the current generation occurs. The resistance of CSM 3 bioelectrode is below the resistance of CSMs 1 and 2 both before (39.6 kΩ/cm2 for CSM 3, 630 Ω/cm2 for CSM 2, and 1329 Ω/cm2 for CSM 1) and after the addition of the substrate (2.9 kΩ/cm2 for CSM 3, 45 kΩ/cm2 for CSM 2, and 58 kΩ/cm2 for CSM 1). The bioelectrode made of CSM 3 has a capacitance of 196 μF/cm2—greater than two orders of magnitude of the bioelectrode capacity of CSMs 1 and 2 (0.51 and 0.58 μF/cm2, respectively). It is important to further study the properties of the CSM class of materials, which are promising as the basis of mechanically flexible electrodes with controlled parameters.

The process of template-free DNA synthesis was detected in two ways: by measuring the pH of the solution by a semiconductor sensor and by measuring the conductivity in the recording of impedance spectra. Synthesis was carried out without using template DNA, with only two enzymes being involved in the reaction: DNA polymerase and nicking endonuclease (nickase) in the presence of deoxynucleotide triphosphates. Previously, Purushothaman et al., by applying the recording of the results of template-directed synthesis with a pH-sensitive field-effect transistor, showed that protons are released into solution in the incorporation of nucleotides [4]. Regarding this, it was important to establish that the same release of protons into solution occurred in the template-free synthesis as in the template-directed synthesis and to identify the changes by measuring the conductivity of the solution using impedance spectra. It was found that the template-free synthesis was accompanied by the generation of protons (ΔpH is ~1.5 pH at an initial concentration of deoxynucleotide triphosphates of 150 µM) and a decrease in the value of active impedance component by ~25% of the initial value. The effect of a decrease in the active impedance component was explained as being due to an increasing conductivity of medium due to a growth in the concentration of protons.

Neurodegenerative diseases are now the most debilitating disorders affecting the human population. In recent times, neurodegenerative diseases have become the fourth leading cause of death after heart disease, cancer, and stroke. Neurodegenerative diseases affect the thinking, skilled movements, feelings, cognitive behavior, and memory of a person, resulting in short-term and long-term impairment and disabilities. Neurodegenerative diseases include serious disorders like Alzheimer’s disease, Parkinson’s disease, dementia, and other rare disorders like amyotrophic lateral sclerosis, Huntington’s disease, and prion diseases. Although a century has passed since the discovery of neurodegenerative diseases, there is still a need for more diagnostic approaches and effective cure. The emerging field of nanotechnology promises new techniques to solve some of the challenges in this field. Nanotechnological tools enable drugs to cross the blood–brain barrier and target the site of action in a specific manner. The new generation nanoparticles could also be useful in the treatment of brain diseases. In the present chapter, we explain the way ahead for nanotechnology for the treatment of neurodegenerative disorders.