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With the rapid development of modern industry, it is urgently needed to measure the biotoxicity of complex chemicals. Microbial electrochemical biotoxicity sensors are an attractive technology; however, their application is usually limited by their stability and reusability after measurements. Here, we improve their performance by encapsulating the electroactive biofilm with polydopamine (PDA), and we evaluate the improvement by different concentrations of heavy metal ions (Cu2+, Ag+, and Fe3+) in terms of inhibition ratio (IR) and durability. Results indicate that the PDA-encapsulated sensor exhibits a more significant detection concentration than the control group, with a 3-fold increase for Cu2+ and a 1.5-fold increase for Ag+. Moreover, it achieves 15 more continuous toxicity tests than the control group, maintaining high electrochemical activity even after continuous toxicity impacts. Images from a confocal laser scanning microscope reveal that the PDA encapsulation protects the activity of the electroactive biofilm. The study, thus, demonstrates that PDA encapsulation is efficacious in improving the performance of microbial electrochemical biotoxicity sensors, which can extend its application to more complex media. [ABSTRACT FROM AUTHOR]

With the rapid development of modern industry, it is urgently needed to measure the biotoxicity of complex chemicals. Microbial electrochemical biotoxicity sensors are an attractive technology; however, their application is usually limited by their stability and reusability after measurements. Here, we improve their performance by encapsulating the electroactive biofilm with polydopamine (PDA), and we evaluate the improvement by different concentrations of heavy metal ions (Cu2+, Ag+, and Fe3+) in terms of inhibition ratio (IR) and durability. Results indicate that the PDA-encapsulated sensor exhibits a more significant detection concentration than the control group, with a 3-fold increase for Cu2+ and a 1.5-fold increase for Ag+. Moreover, it achieves 15 more continuous toxicity tests than the control group, maintaining high electrochemical activity even after continuous toxicity impacts. Images from a confocal laser scanning microscope reveal that the PDA encapsulation protects the activity of the electroactive biofilm. The study, thus, demonstrates that PDA encapsulation is efficacious in improving the performance of microbial electrochemical biotoxicity sensors, which can extend its application to more complex media.

Microbial fuel cell (MFC)-based biosensor sensing has emerged as an innovative approach to in situ and immediate monitoring of substrate concentration. MFC-biosensor uses bioanode as a sensing element. In this study, the performance of MFC-biosensor, operated with Pb+2, was studied at different hydraulic retention times (HRTs). The HRT ranges were 0.5, 1, and 2 days. The power density generation increased with the decreasing HRT. The highest achievable power density was obtained at HRT of 1 days with the density value of 597 mW/m2. The power density produced in the MFC system was stored in the energy storage system. The computational fluid dynamics (CFD) method simulates detailed three-dimensional flow and heat transfer properties in reactors and provides information about potential reactor design. CFD was chosen to simulate the concentration distribution of the substrate in the MFC in different reactor type and different HRTs. It was observed that there was good turbulence in the reactor in a two day HRT and the reactor volume was used effectively. Life cycle assessment (LCA) was performed at 1 day with the highest power density. An LCA was implemented to the production and operation processes of a microbial fuel cell. According to the results, these two processes caused 4.23 × 10−6 loss of healthy years, extinction of 1.3 × 10−8 species in a year and loss of $ 0.33 source availability. The emissions to air, water, and soil were also calculated. These results showed that MFC-biosensor provided information on the rate of biodegradation processes. [ABSTRACT FROM AUTHOR]

Microbial biosensors can be an excellent alternative to classical methods for toxicity monitoring, which are time-consuming and not sensitive enough. However, bacteria typically connect to electrodes through biofilm formation, leading to problems due to lack of uniformity or long device production times. A suitable immobilisation technique can overcome these challenges. Still, they may respond more slowly than biofilm-based electrodes because bacteria gradually adapt to electron transfer during biofilm formation. In this study, we propose a controlled and reproducible way to fabricate bacteria-modified electrodes. The method consists of an immobilisation step using a cellulose matrix, followed by an electrode polarization in the presence of ferricyanide and glucose. Our process is short, reproducible and led us to obtain ready-to-use electrodes featuring a high-current response. An excellent shelf-life of the immobilised electrochemically active bacteria was demonstrated for up to one year. After an initial 50% activity loss in the first month, no further declines have been observed over the following 11 months. We implemented our bacteria-modified electrodes to fabricate a lateral flow platform for toxicity monitoring using formaldehyde (3%). Its addition led to a 59% current decrease approximately 20 min after the toxic input. The methods presented here offer the ability to develop a high sensitivity, easy to produce, and long shelf life bacteria-based toxicity detectors.

Abstract Electroactive biofilms (EABs) have recently attracted considerable research interest for their possible use as amperometric biosensors in environmental or bioprocess monitoring, for example for in situ detection of toxic compounds. Almost exclusively, corresponding research has focused on heterotrophic, anodic EABs. These biofilms require sufficiently high organic loads and anoxic conditions to deliver a stable baseline current. Conversely, electroautotrophic O 2 -reducing EABs have recently been proposed to monitor toxic shocks in oxic solutions that are poor or devoid of organic substrate. This was done in optimal media and only assessed for formaldehyde as a model toxic compound. Here we show that O 2 -reducing EABs can grow in unamended tap water on carbon electrodes at + 0.2 V vs. Ag/AgCl. They retained substantial electroactivity for at least eight months without adding exogenous compounds. The most represented operational taxonomic units were assigned to the phylum Gammaproteobacteria (25 ± 15%, n = 5 electrodes). Cyclic voltammograms showed a reproducible nernstian behavior for O 2 reduction with a mid-wave potential at + 0.27 V and variable plateau current densities ranging from – 1 to – 22 µA cm−2 (n = 10 electrodes). The biocatalytic current was substantially impacted by the addition of either of three tested heavy metals (Hg(II), Cr(VI) or Pb(II)) or by organic pollutants (formaldehyde, 2,4-dichlorophenol, benzalkonium chloride), with limits of detection ranging from 0.5 to 10 mg L−1 (2.5–61 µmol L−1). Response times were typically around 1 min. Comparison with previous reports suggests that O 2 -reducing microbial cathodes may be more sensitive to toxic shocks than anodic, heterotrophic EABs. Highlights • Electroactive biofilms electroreducing O 2 at high potential could grow in tap water. • Microbially-induced current generated for more than 8 months in unamended tap water. • Toxic shocks monitored amperometrically for 6 heavy metals and organic pollutants. • Results suggest that cathodic biofilms are more sensitive than anodic to toxicants. [ABSTRACT FROM AUTHOR]

The US Army's need for a reliable and field-portable drinking water toxicity sensor was the catalyst for the development and evaluation of an electric cell-substrate impedance sensing (ECIS) device. Water testing technologies currently available to soldiers in the field are analyte-specific and have limited capabilities to detect broad-based water toxicity. The ECIS sensor described here uses rainbow trout gill epithelial cells seeded on fluidic biochips to measure changes in impedance for the detection of possible chemical contamination of drinking water supplies. Chemicals selected for testing were chosen as representatives of a broad spectrum of toxic industrial compounds. Results of a US Environmental Protection Agency (USEPA)-sponsored evaluation of the field portable device were similar to previously published US Army testing results of a laboratory-based version of the same technology. Twelve of the 18 chemicals tested following USEPA Technology Testing and Evaluation Program procedures were detected by the ECIS sensor within 1 h at USEPA-derived human lethal concentrations. To simplify field-testing methods further, elimination of a procedural step that acclimated cells to serum-free media streamlined the test process with only a slight loss of chemical sensitivity. For field use, the ECIS sensor will be used in conjunction with an enzyme-based sensor that is responsive to carbamate and organophosphorus pesticides. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

[Display omitted] • Real-time measuring unit of input stream toxicity to bioreactors was developed. • The automatic sensing unit is based on viability assay using bacillus subtilis. • The sensing unit was integrated with a photocatalytic reactor. • An autonomous control of the work-load of a photocatalytic reactor was achieved. • The approach can be utilized to any AOP-biotreatment tandem configuration. Wastewater streams contain a large number of contaminants, part of which can be quite toxic for the working bacteria in bioreactors, thus hampering its efficiency. In such cases, pretreatment by an Advanced Oxidation Process (AOP) might be needed. Since, in general, biotreatment is more economic than AOP, it is sensible to design the integrated system in a manner that would reduce the load on the AOP as much as possible. This is a very challenging task, since the type and the concentration of the toxic compounds constantly varies over time. The problem is aggravated by lack of inexpensive and fast technologies that are able to evaluate the toxicity under conditions in which the nature of the toxic compounds is unknown. Here we report on the developing of a unit that automatically measures the extent by which polluted water might put at risk a biological treatment unit. The sensing unit monitors in real time the viability of the reporting bacteria Bacillus Subtilis , using resazurin. The toxic compounds were modelled by three antibiotics (chloramphenicol, tetracycline and ciprofloxacin). The potential of embedding the sensing unit in a multi-technology system (AOP-biological) was demonstrated by connecting the sensing unit to a photocatalytic reactor and controlling the number of operating lamps in the photocatalytic reactor autonomously according to predetermined toxicity setpoint. The approach can be easily applied to almost any AOP-biotreatment tandem system, while altering any controllable parameter (residence time, light, etc.) of the AOP unit according to needs. [ABSTRACT FROM AUTHOR]

Abstract: We report the fabrication and use of electrodes constructed from single walled carbon nanotubes (SWCNTs) chemically assembled on a carbon surface and functionalised with an osmium(II) bipyridine complex (Osbpy). The ability of the electrodes to transduce biologically generated currents from Proteus vulgaris has been established. Our investigations show that there are two contributions to the current: one from electroactive species secreted into solution and another from cell redox sites. The modified electrode can be used to monitor cell metabolism, thereby acting as a whole cell biosensor. The biosensor was used in a 1-h assay to investigate the toxicity of ethanol, sodium azide and the antibiotic ampicillin and gave quantitative data that were closely correlated with standard cell plate viability assays. The results provide proof of principle that the whole cell biosensor could be used for high throughput screening of antimicrobial activity. One of the modified electrodes was used for approximately 1000 measurements over four months demonstrating the robustness of the system. [ABSTRACT FROM AUTHOR]

The article presents a study which improves toxicant responsiveness and field portability of bovine pulmonary artery endothelial cell (BPAEC) monolayer electrical impedance with electric cell-substrate impedance sensing (ECIS). The study screens several cells for sensitivity to 12 waterborne industrial chemicals. The result shows that bovine lung microvessel endothelial cell (BLMVEC) monolayers and iguana heart (IgH-2) cell monolayer detect nine wateborne industrial chemicals.

Abstract: Comprehensive identification of chemical contaminants in Army field water supplies can be a lengthy process, but rapid analytical methods suitable for field use are limited. A complementary approach is to directly measure toxicity instead of individual chemical constituents. Ten toxicity sensors utilizing enzymes, bacteria, or vertebrate cells were tested to determine the minimum number of sensors that could rapidly identify toxicity in water samples containing one of 12 industrial chemicals. The ideal sensor would respond at a concentration just exceeding the Military Exposure Guideline (MEG) level for the chemical (an estimated threshold for adverse effects) but below the human lethal concentration. Chemical solutions were provided to testing laboratories as blind samples. No sensors responded to deionized water blanks, and only one sensor responded to a hard water blank. No single toxicity sensor responded to more than six chemicals in the desired response range, and one chemical (nicotine) was not detected by any sensor with the desired sensitivity. A combination of three sensors (Microtox, the Electric Cell Substrate Impedance Sensing (ECIS) test, and the Hepatocyte low density lipoprotein (LDL) uptake test) responded appropriately to nine of twelve chemicals. Adding a fourth sensor (neuronal microelectrode array) to the test battery allowed detection of two additional chemicals (aldicarb and methamidophos), but the neuronal microelectrode array was overly sensitive to paraquat. Evaluating sensor performance using a standard set of chemicals and a desired sensitivity range provides a basis both for selecting among available toxicity sensors and for evaluating emerging sensor technologies. Recommendations for future toxicity sensor evaluations are discussed. [Copyright &y& Elsevier]

Microbial fuel cell (MFC) sensor exhibits attractive prospects for online monitoring of water toxicity as an early warning device. However, the accumulation of dead cells in anode biofilm might decrease the sensing sensitivity of MFC during long term operation. In addition, with repeated exposure to toxins, the microbial community of anode biofilm would also adjust to build up higher endurance to environmental toxicity. In this study, the long term sensing sensitivity of MFC sensor and the microbial community changes were characterized with Pb2+ as the target toxin. The results show that newly formed biofilm with higher live/dead cell ratio exhibited higher sensitivity than mature biofilm. Modification of anodic biofilm via high current stimulation was applied to increase the ratio of live cells, which led to enhanced sensing sensitivity of MFC with mature anode biofilm. However, the enhancement was relatively limited for biofilm that was previously exposed to repeated Pb2+ shocks. Microbial community analysis revealed that the proportions of microbial species possessing higher environmental robustness, such as Hyphomicrobiaceae and Cloacibacillus , significantly increased in the anode biofilm after long term repeated Pb2+ shocks. • Long term performance of MFC based Pb2+ shock sensor was evaluated. • Newly formed biofilm exhibited higher sensitivity than mature biofilm. • High current stimulation was able to enhance sensing sensitivity of MFC sensor. • Increased robustness of anode biofilm observed under long term repeated Pb2+ shocks. [ABSTRACT FROM AUTHOR]

MFC toxicity sensor has major hindrances that limit its practical application, such as the poor concentration-response relationship and inferior recovery capability after high toxicity shock. Till now, the direct influence of intrinsic properties on the performance of MFC toxicity sensor has not been well understood. Quorum sensing (QS) is a cell-to-cell communication strategy that indirectly affects the intrinsic properties of electroactive biofilms. In this work, commercially available QS autoinducers (AHLs) were applied to MFC toxicity sensor to manipulate anode biofilm for better sensing performance. The results showed that the addition of AHLs (C6-HSL, 3-OXO-C12-HSL) led to higher sensing linearity to a wider range of Pb2+. The voltage of MFC sensors with AHLs addition fully recovered even after 10 mg/L Cu2+ shock, indicating an enhanced recovery capability of MFC toxicity sensor. It was found that higher live/dead cells ratio and increased exoelectrogen Geobacter abundance were responsible for the superior sensing linearity and recovery capability of MFC toxicity sensor. Our work presented a novel and effective way to advance the process of MFC toxicity sensor application from the perspective of EABs. Image 1 • The influence of QS on MFC sensing performance was studied for the first time. • Enhanced QS increased the sensing linearity of MFCs to Pb2+ sensing. • MFCs with enhanced QS had better recovery capability to high toxicity Cu2+ shock. [ABSTRACT FROM AUTHOR]

Microbial biosensors can be an excellent alternative to classical methods for toxicity monitoring, which are time-consuming and not sensitive enough. However, bacteria typically connect to electrodes through biofilm formation, leading to problems due to lack of uniformity or long device production times. A suitable immobilisation technique can overcome these challenges. Still, they may respond more slowly than biofilm-based electrodes because bacteria gradually adapt to electron transfer during biofilm formation. In this study, we propose a controlled and reproducible way to fabricate bacteria-modified electrodes. The method consists of an immobilisation step using a cellulose matrix, followed by an electrode polarization in the presence of ferricyanide and glucose. Our process is short, reproducible and led us to obtain ready-to-use electrodes featuring a high-current response. An excellent shelf-life of the immobilised electrochemically active bacteria was demonstrated for up to one year. After an initial 50% activity loss in the first month, no further declines have been observed over the following 11 months. We implemented our bacteria-modified electrodes to fabricate a lateral flow platform for toxicity monitoring using formaldehyde (3%). Its addition led to a 59% current decrease approximately 20 min after the toxic input. The methods presented here offer the ability to develop a high sensitivity, easy to produce, and long shelf life bacteria-based toxicity detectors., (© 2020 The Author(s).)

Bioluminescence of isolated enzymes is a perspective phenomenon for biosensors development due to simplicity of registration of a physiological parameter - light intensity. Enzyme-based bioluminescent assay is widely used to evaluate a decrease in biochemical toxicities. Also the enzyme-based assay is used for the direct biochemical monitoring of oxidative toxicity. This work considers antioxidant properties of fullerenols, water-soluble polyhydroxylated derivatives of fullerenes and perspective pharmaceutical agents, in solutions of model inorganic and organic toxicants of oxidative type – K 3 [Fe(CN) 6 ] and 1,4-benzoquinone. Two fullerenol preparations were used: C 60 O 2-4 (OH) 20-24 and mixture of two types of fullerenols C 60 O 2-4 (OH) 20-24 +C 70 O 2-4 (OH) 20-24 . The enzyme-based assays showed the peculiarities of the detoxification processes: ultralow concentrations of fullerenols were active ( ca 10 -17 -10 -5 g/L); no monotonic dependence of detoxification efficiency on fullerenol concentrations was observed, and detoxification of organic oxidizer solutions was more effective than that of the inorganic oxidizer. The antioxidant effects of highly diluted fullerenol solutions were attributed to hormesis phenomenon; the detoxification was concerned with stimulation of adaptive cellular response under low-dose exposures. [ABSTRACT FROM AUTHOR]

Microbial fuel cells (MFCs) is a highly promising bioelectrochemical technology and uses microorganisms as catalyst to convert chemical energy directly to electrical energy. Microorganisms in the anodic chamber of MFC oxidize the substrate and generate electrons. The electrons are absorbed by the anode and transported through an external circuit to the cathode for corresponding reduction. The flow of electrons is measured as current. This current is a linear measure of the activity of microorganisms. If a toxic event occurs, microbial activity will change, most likely decrease. Hence, fewer electrons are transported and current decreases as well. In this way, a microbial fuel cell-based biosensor provides a direct measure to detect toxicity for samples. This paper introduces the detection of antibiotics, heavy metals, organic pollutants and acid in MFCs. The existing problems and future application of MFCs are also analyzed.