Polyvinyl alcohol (PVA) hydrogels modified through radical polymerization under UV irradiation and Ce4+ ion treatment were investigated as a potential platform for developing highly sensitive biosensors for rapid biochemical oxygen demand analysis in water. These modifications enhance PVA physicochemical properties, including mechanical strength, stability, and biocompatibility, making it promising for immobilizing microorganisms in bioanalytical systems. A dual-mediator biosensor system using ferrocene (FC) and neutral red (NR) was developed with yeast Blastobotrys adeninivorans immobilized in modified PVA. The FC+NR-B. adeninivorans-PVA-Ce4+ system exhibited high sensitivity (linear range of 0.1-3.81 mgO2/dm3), selectivity, and operational stability (up to 37 days service life), outperforming existing analogs. Testing with wastewater confirmed strong correlation with standard BOD5, highlighting the potential for monitoring water quality. The described radical modification method is a simple and effective approach for creating sensitive and stable biosensors. It opens up new possibilities for environmental monitoring technology.

This article presents the development of an electrochemical biosensor based on conductive polymers and microorganisms for rapid and sensitive detection of surfactants in aqueous media. The study includes a systematic comparative investigation of several conductive polymers (poly(neutral red) pNR, poly(thionine) pTN, polypyrrole PPy, polyaniline PANI, and PEDOT:PSS) and selection of the optimal conductive polymer (pNR) and microorganism (Pseudomonas putida VKM B-973) as well as investigation of their interaction rates and electrochemical properties. Modification of electrodes with carbon nanomaterials such as single-walled carbon nanotubes (SWCNT) has been shown to significantly improve the sensitivity (lower limit of detectable concentration is 0.061 mg/dm3) and stability (microbial sensor can function for 15 days with relative standard deviation of analytical signal being 5.4 %) of the biosensor. The device is used for detecting anionic surfactant in river water samples and the results obtained are statistically insignificant from those obtained by the conventional method of analysis.

The growing threat of organic pollution to surface waters necessitates the development of rapid and scalable monitoring tools that transcend the limitations of the standard 5-day biochemical oxygen demand (BOD5) test. This study presents a novel approach by developing a highly stable and rapid BOD biosensor based on the microorganism Paracoccus yeei, immobilized within a sol–gel-derived xerogel matrix synthesized on a polyhydroxybutyrate (PHB) substrate. The PHB-supported xerogel significantly enhanced microbial viability and sensor stability. This biosensor demonstrated a correlation (R2 = 0.93) with the standard BOD5 method across 53 diverse water samples from the Tula region, Russia, providing precise results in just 5 min. The second pillar of our methodology involved analyzing multi-year Landsat satellite imagery via the Global Surface Water Explorer to map hydrological changes and identify zones of potential anthropogenic impact. The synergy of rapid ground-truth biosensor measurements and remote sensing analysis enabled a comprehensive spatial assessment of water quality, successfully identifying and ranking pollution sources, with wastewater discharges and agro-industrial facilities constituting the most significant factors. This work underscores the high potential of PHB–xerogel composites as efficient immobilization matrices and establishes a powerful, scalable framework for regional environmental monitoring by integrating advanced biosensor technology with satellite observation.

A biosensor for the determination of glucose, lactate, ethanol and starch in beverages has been developed using enzymes immobilized by a redox-active gel on a screen-printed electrode. A significant improvement proposed for multichannel biosensors, overcoming stability and sensitivity issues by covalently binding phenazine mediators to a biocompatible protein hydrogel, enhancing the packaging of the enzyme. Glucose oxidase (GOx), alcohol oxidase (AOx) and lactate oxidase (LOx) were used as biological materials, as well as a mixture of GOx with γ-amylase (Am). Redox gels were synthesized from bovine serum albumin (BSA) and phenazine derivatives. It was shown that a neutral red-based redox gel combined with single-walled carbon nanotubes is more promising than other substrates for enzyme immobilization. The lower limit of quantification for glucose, ethanol, lactate and starch using these systems is 0.035 mM, 2.3 mM, 15 mM and 2 mg/L, respectively. Biosensors were used to analyze the content of these substances in alcoholic, kvass and fermentation mass. Statistical analysis of the results showed that the values of glucose, ethanol, lactic acid and starch determined using biosensors and obtained by reference methods differ insignificantly. A set of biosensors developed on the basis of specifically selected enzymes is effective for controlling biotechnological processes and can be used as an alternative to classical analytical methods.

Natural and modified clay minerals are widely used in environmental technologies to remove a wide range of toxic substances from aquatic and soil ecosystems. This study assessed the toxicity of synthesized organoclays compared to pure bentonite using microbiological, phytotoxic, and instrumental (biosensor) methods. Organoclay containing lauramine oxide (a non-ionic surfactant) was found to have an increased toxic effect on all test organisms analyzed. Based on the phytotesting parameters, radish was found to be the most sensitive test organism in these experiments, as it was significantly affected by toxic substances, demonstrating noticeable changes in its morphology and morphometry. Minimal toxicity was demonstrated for organoclay containing alkyl polyglucoside (a non-ionic surfactant), which was used in all tests. Furthermore, organoclay containing disodium cocoamphodiacetate (an amphoteric surfactant) also exhibited minimal toxicity in phytotesting, including germination assessment (radish) and evaluation of morphometric characteristics using a biosensor method. The study confirms that the type of organic modifier significantly impacts the biocompatibility of organoclays. Using fewer toxic surfactants can improve the environmental acceptability of these materials for use in cleaning up contaminated ecosystems.

Microbial biosensors are bioanalytical devices that can measure the toxicity of pollutants or detect specific substances. This is the greatest advantage of microbial biosensors which use whole cells of microorganisms as powerful tools for measuring integral parameters of environmental pollution. This review explores the core principles of microbial biosensors including biofuel devices, emphasizing their capacity to evaluate biochemical oxygen demand (BOD), toxicity, heavy metals, surfactants, phenols, pesticides, inorganic pollutants, and microbiological contamination. However, practical challenges, such as sensitivity to environmental factors like pH, salinity, and the presence of competing substances, continue to hinder their broader application and long-term stability. The performance of these biosensors is closely tied to both technological advancement and the scientific understanding of biological systems, which influence data interpretation and device optimization. The review further examines cutting-edge developments, including the integration of electroactive biofilms with nanomaterials, molecular biology techniques, and artificial intelligence, all of which significantly enhance biosensor functionality and analytical accuracy. Commercial implementations and improvement strategies are also discussed, providing a comprehensive overview of the state-of-the-art in this field. Overall, this work consolidates recent progress and identifies both the potential and limitations of microbial biosensors, offering valuable insights into their future development for environmental monitoring.

A biosensor for the determination of the phenol index in water bodies has been developed using enzymes immobilized on the redox-active polymer surface of a graphite paste electrode. Tyrosinase, laccase, and bacterial cell membrane fractions were used as biological materials. Redox polymers based on bovine serum albumin (BSA) and various electron transport mediators were synthesized for immobilization. It has been shown that a redox polymer based on ferrocene (FC) combined with single-walled carbon nanotubes (SWCNTs) is more promising for use in biosensors than a polymer based on safranin (SAF) based on electrochemical and analytical parameters. The best results were obtained with the “BSA-FC-SWCNT-tyrosinase” bioanalytical system, which has a lower limit of detectable concentrations of 1 × 10⁻³ mg/L, indicating the possibility of monitoring water environments with a phenol concentration corresponding to the maximum permissible concentration (MPC). The maximum analytical signal was generated at a temperature of 30 °С and a pH of 6.8. The biosensor was stable at concentrations of heavy metal ions up to 100 times the MPC, as well as at NaCl concentrations up to 5

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.

This review analyzes the main methods for cleaning up oil pollution in natural ecosystems, with a particular focus on the synergy between chemical and microbiological techniques for environmental remediation. While biological methods are a green and inexpensive soil remediation technique, they have a major limitation in their inability to clean up high concentrations of toxic contaminants. The poor performance of chemical methods stems from the high cost of chemicals and concerns over their negative and toxic effects on the environment. Physical methods also have high costs due to energy consumption and the need for additional treatment of gases generated during decontamination, making them ineffective for soil remediation. The main principle of bioremediation is based on microorganisms’ ability to degrade complex organic compounds, such as petroleum. This process is described in this review. This combination of methods allows for a higher level of decontamination of soil and water ecosystems, even against pollutants that are usually resistant to degradation, such as oil derivatives. While existing methods for cleaning oil-contaminated ecosystems are highly effective, they require significant material costs to implement. Additionally, the review discusses how the joint use of current and future biotechnology techniques can lead to the development of an effective set of strategies to protect soil and water systems from oil pollution. The reviewed studies show that a hybrid biotechnological approach is the most effective remediation method. When biological decontamination methods are adopted, the optimized combination of different remediation strategies can overcome the limitations of each technique, allowing efficiencies of even more than 70% to be achieved, given that the choice still depends on the type of contaminant, its concentration, and the properties of the receiving substrate.

This work proposes a new method for forming a biosensor based on a nanopillar copper electrode and microorganisms for rapid assessment of the biochemical oxygen demand (BOD) index. Heterogeneous electron transfer constants were obtained for water-soluble and insoluble redox-compounds, and single-mediator and dual-mediator bioelectrochemical systems were formed taking into account the obtained values. It was shown that the yeast Debaryomyces hansenii is not susceptible to the toxic effect of copper and could be effectively used with a nanostructured electrode in the ferrocene-methylene blue dual-mediator system. Paracoccus yeei bacteria are susceptible to the toxic effect of copper ions, therefore, their immobilization on the nanostructured electrode was carried out using the redox-active polymer poly(neutral red), which protects microorganisms from negative effects and allows effective conjugation of microorganisms with the surface. The developed bioelectrochemical measuring systems have high sensitivity (the lower limit of determined BOD5 values is 2.0 mg dm(-3)) and high correlation with the standard method for BOD measurement in surface water samples (R-2 > 0.98). Thus, the work demonstrated for the first time the successful use of a metal nanopillar electrode as a substrate for the biosensor, and the created biosensor systems could serve as prototypes of commercially available miniature sensors for rapid assessment of water quality. The cost of the biosensor of the developed bioelectrochemical measuring systems was estimated: for a two-mediator system based on D. hansenii microorganisms and ferrocene-methylene blue mediators, the cost of one bioelectrode was 4.28 USD, and for a system based on P. yeei microorganisms and poly(neutral red) - 3.91 USD.

Amperometric biosensors have emerged as a cutting-edge technology in clinical diagnostics, thanks to their high level of sensitivity, rapid analytical results, compact size, and ability to monitor health parameters non-invasively and continuously using flexible and wearable sensors. This review explores the latest developments in the field of amperometric biosensing for medical applications. It discusses the materials used to construct these sensors and pays particular attention to biosensors designed to measure glucose, lactate, cholesterol, urea, and uric acid levels. The review also addresses the technological limitations and drawbacks of these devices. Furthermore, it presents the current status and identifies future trends in the development of flexible, wearable biosensors capable of providing continuous monitoring of a patient's health status.

Biofilms based on bacteria Pseudomonas veronii (Ps. veronii) and Escherichia coli (E. coli) and yeast Saccharomyces cerevisiae (S. cerevisiae) were used for novel biosensor creation for rapid biochemical oxygen demand (BOD) monitoring. Based on the electrochemical measurement results, it was shown that the endogenous mediator in the matrix of E. coli and Ps. veronii biofilms and ferrocene form a two-mediator system that improves electron transport in the system. Biofilms based on Ps. veronii and E. coli had a high biotechnological potential for BOD assessment; bioreceptors based on such biofilms had high sensitivity (the lower limits of detectable BOD5 concentrations were 0.61 (Ps. veronii) and 0.87 (E. coli) mg/dm3) and high efficiency of analysis (a measurement time 5–10 min). The maximum biosensor response based on bacterial biofilms has been observed in the pH range of 6.6–7.2. The greatest protective effect was found for biofilms based on E. coli, which has high long-term stability (151 days for Ps. veronii and 163 days for E. coli). The results of the BOD5 analysis of water samples obtained using the developed biosensors had a high correlation with the results of the standard 5-day method (R2 = 0.9820, number of tested samples is 10 for Ps. veronii, and R2 = 0.9862, number of tested samples is 10 for E. coli). Thus, biosensors based on Ps. veronii biofilms and E. coli biofilms could be a novel analytical system to give early warnings of pollution.

This work proposes an approach to the formation of receptor elements for the rapid diagnosis of the state of surface waters according to two indicators: the biochemical oxygen demand (BOD) index and toxicity. Associations among microorganisms based on the bacteria P. yeei and yeast S. cerevisiae, as well as associations of the yeasts O. polymorpha and B. adeninivorans, were formed to evaluate these indicators, respectively. The use of nanocomposite electrically conductive materials based on carbon nanotubes, biocompatible natural polymers—chitosan and bovine serum albumin cross-linked with ferrocenecarboxaldehyde, neutral red, safranin, and phenosafranin—has made it possible to expand the analytical capabilities of receptor systems. Redox polymers were studied by IR spectroscopy and Raman spectroscopy, the contents of electroactive components were determined by atomic absorption spectroscopy, and electrochemical properties were studied by electrochemical impedance and cyclic voltammetry methods. Based on the proposed kinetic approach to modeling individual stages of bioelectrochemical processes, the chitosan–neutral red/CNT composite was chosen to immobilize the yeast association between O. polymorpha (ks = 370 ± 20 L/g × s) and B. adeninivorans (320 ± 30 L/g × s), and a bovine serum albumin (BSA)–neutral composite was chosen to immobilize the association between the yeast S. cerevisiae (ks = 130 ± 10 L/g × s) and the bacteria P. yeei red/CNT (170 ± 30 L/g × s). After optimizing the composition of the receptor systems, it was shown that the use of nanocomposite materials together with associations among microorganisms makes it possible to determine BOD with high sensitivity (with a lower limit of 0.6 mg/dm3) and detect the presence of a wide range of toxicants of both organic and inorganic origin. Both receptor elements were tested on water samples, showing a high correlation between the results of biosensor analysis of BOD and toxicity and the results of standard analytical methods. The results obtained show broad prospects for creating sensitive and portable bioelectrochemical sensors for the early warning of environmentally hazardous situations based on associations among microorganisms and nanocomposite materials.

For many decades, natural and modified clay minerals have been used as adsorbents to clean up aquatic and soil ecosystems contaminated with organic and inorganic pollutants. In this study, organoclays based on bentonite and various amphoteric and nonionic surfactants were synthesized and tested as effective sorbents for lead ions. The maximum values of R were obtained when describing the sorption processes using the Langmuir model, which ranged from 0.97 to 0.99. The adsorption of lead ions by these organoclays was investigated using different sorption models including the Langmuir, Freundlich, and BET. It was found that, according to the values of limiting adsorption to the Langmuir equation, the synthesized organoclays formed an increasing series: organoclay with cocamide diethanolamine < bentonite < organoclay with lauramine oxide < organoclay with sodium cocoiminodipropionate < organoclay with disodium cocoamphodiacetate < organoclay with alkyl polyglucoside. The Gibbs energy for all of the analyzed samples was calculated and found to be negative, indicating the spontaneity of the cation adsorption process in the forward direction. The maximum value of the adsorption capacity of lead cations on organoclay-based bentonite with alkyl polyglucoside was 1.49 ± 0.05 mmol/g according to the Langmuir model, and 0.523 ± 0.003 mmol/g as determined by the BET model. In the process of modifying bentonite, there was an increase in negative values of the zeta potential for organoclays compared to the initial mineral, which clearly enhanced their electrostatic interactions with the positively charged lead ions. It was hypothesized, based on the physicochemical principles, that exchange adsorption is the main mechanism for lead absorption. Based on chemical approaches, organoclays based on amphoteric surfactants absorb lead mainly through the mechanisms of electrostatic attraction, ion exchange, and complexation as well as the formation of insoluble precipitates. Organoclays based on nonionic surfactants, on the other hand, absorb lead through mechanisms of complexation (including chelation) and the formation of insoluble chemical precipitates. The comparison of isotherms from different models allows us to find the most accurate match between the model and the experimental data, and to better understand the nature of the processes involved.

In this study, we introduce an efficient approach to cross-disciplinary glucose biosensor technology through the development of hybrid nanocomposite materials. These materials were crafted from redox-active polymers embedded in silica sol-gel matrices, intricately linked with phenazine mediators and reinforced with carbon nanotubes. By leveraging advanced analytical techniques, including NMR spectroscopy, scanning electron microscopy, and confocal microscopy, we characterized the structures of these redox-active polymers. Our investigation further addressed their electrochemical behaviors by employing cyclic voltammetry and impedance spectroscopy to elucidate their distinctive properties. Employing a complex analytical strategy and a computational approach, this study identified an optimal redox-active system that shows synergy between multiwalled nanotubes and engineered redox-active polymers. This polymer, which is composed of (3-aminopropyl)triethoxysilane and tetraethoxysilane at an optimized ratio of 20:80 vol %, is seamlessly integrated with a covalently bonded neutral red mediator. The resulting biosensor is capable of detecting glucose across a range of 0.01-0.92 mM with a low detection limit of 0.003 mM. Its operational stability is 1.9%, coupled with an unparalleled selectivity that holds promise for further enhancement through machine learning techniques. This machine learning breakthrough represents a significant leap forward in the accurate quantification of glucose in diverse samples, achieving a high degree of correlation with established methods. The composite material revealed in this research has implications for further applications in biosensing technology. The biocompatibility, nontoxicity, stability, and superior conductivity of the material underscore its potential in the field, opening possibilities for the development of blood glucose measurement techniques.

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.

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.

The possibility of using the microorganisms Pseudomonas sp. 7p-81, Pseudomonas putida BS394(pBS216), Rhodococcus erythropolis s67, Rhodococcus pyridinivorans 5Ap, Rhodococcus erythropolis X5, Rhodococcus pyridinivorans F5 and Pseudomonas veronii DSM 11331T as the basis of a biosensor for the phenol index to assess water environments was studied. The adaptation of microorganisms to phenol during growth was carried out to increase the selectivity of the analytical system. The most promising microorganisms for biosensor formation were the bacteria P. putida BS394(pBS216). Cells were immobilized in redox-active polymers based on bovine serum albumin modified by ferrocenecarboxaldehyde and based on a composite with a carbon nanotube to increase sensitivity. The rate constants of the interaction of the redox-active polymer and the composite based on it with the biomaterial were 193.8 and 502.8 dm3/(g·s) respectively. For the biosensor created using hydrogel bovine serum albumin-ferrocene-carbon nanotubes, the lower limit of the determined phenol concentrations was 1 × 10−3 mg/dm3, the sensitivity coefficient was (5.8 ± 0.2)∙10−3 μA·dm3/mg, Michaelis constant KM = 230 mg/dm3, the maximum rate of the enzymatic reaction Rmax = 217 µA and the long-term stability of the bioanalyzer was 11 days. As a result of approbation, it was found that the urban water phenol content differed insignificantly, measured by creating a biosensor and using the standard photometric method.