Water Toxicity Detection Research Articles

Instant water toxicity detection based on magnetically-constructed electrochemically active biofilm

Water toxicity determination with electrochemically active bacteria (EAB) is promising in the early warning of water pollution. However, limited by tedious biofilm formation, natural EAB biofilms are uncapable of the instant detection of water toxicity, resulting in the failure for the emergency monitoring of water pollution. To solve this problem, a novel method for the rapid construction of EAB biofilms using magnetic adsorption was established, and the performance of instant water toxicity detection with magnetically-constructed EAB biofilm was investigated. The results demonstrate that EAB biofilms were magnetically constructed in less than 30 min, and magnetically-constructed EAB biofilm generated stable currents even under continuous flow conditions. Magnetically-constructed EAB biofilms realized instant water toxicity detection, and the sensitivity increased with the decrease of magnetic field intensity. Low magnetic field intensity resulted in a loose biofilm structure, which is conducive to toxic pollutant penetration. The detection limit for Cu2+, phenol, and Cd2+ achieved 0.07 mg/L with optimal magnetic field intensity, and the detection time was less than 30 min. This study broadens the application of water toxicity determination with EAB, and establishes a foundation for the instant and continuous detection of water toxicity with EAB.

Innovative electrochemical biosensor with nitrifying biofilm and nitrite oxidation signal for comprehensive toxicity detection in Tuojiang River

Water toxicity detection, as a valuable supplement to conventional water quality measurement, is an important method for evaluating water environmental quality standards. However, the toxicity of composite pollutants is more complicated due to their mixture effects. This study developed a novel, rapid and interference-resistant detection method for water toxicity based on an electrochemical biosensor using peak current from nitrite oxidation as a signal. Toxicants could weaken the characteristic peak current of nitrite to indicate the magnitude of toxicity. The proof-of-concept study was first conducted using a synthetic water sample containing trichloroacetic acid (TCAA), and then the results were compared with those of the traditional toxicity colorimetric method (CCK-8 kit) and laser confocal microscopy (CLSM). The accuracy of the biosensor was further verified with water samples containing individual pollutants such as Cd2+ (50–150 μg/L), Cr6+ (20–80 μg/L) mixture, triclosan (TCS; 0.1–1.0 μg/L) and TCAA (10–80 μg/L), or a mixture of the above. The viability of the sensor was further validated with the actual water sample from the Tuojiang River. The results demonstrated that although the concentration of a single conventional pollutant in water did not exceed the discharge standard for surface water, the comprehensive toxicity of natural water should not be ignored. This method could be a beneficial supplement to conventional water quality detection to understand the characteristics of the water, and thus contribute to the next stage of water treatment.

Construction of a high power-density microbial fuel cell based on lipopolysaccharide-lectin interactions and its application for detecting heavy metal toxicity

• A Con A/AuNPs/CC electrode was facilely fabricated and used as novel anode material. • The interactions between Con A and bacterial lipopolysaccharide enable fast bacteria inoculation. • The interactions between Con A and bacterial lipopolysaccharide increase the bacterial loading capacity. • The proposed MFC can produce a maximal power density of 3362 mW cm -2 . • The MFC is used as a self-powered biosensor for heavy metal toxicity detection. Herein, we report the short startup time and high power density of a microbial fuel cell (MFC) based on lipopolysaccharide (LPS)-lectin interactions and its application for the detection of heavy metal toxicity. Concanavalin A (Con A) as a typical lectin is immobilized on a carbon cloth (CC) electrode with Au nanoparticles (AuNPs) as the bridge. The interactions between Con A and bacterial LPS can not only accelerate the inoculation speed of Shewanella putrefaciens but also increase the loading capacity of Shewanella putrefaciens on the anode. In addition, AuNPs on the Con A/AuNPs/CC anode can promote the direct extracellular electron transfer. Using the Con A/AuNPs/CC anode, the MFC produces a maximal power density of 3362 ± 120 mW m 2 , which is an order of magnitude higher than a CC anode based MFC. Taking Hg 2+ as an example, the MFC is used as a self-powered biosensor for toxicity detection in water. The output current density of the MFC decreases linearly with the increase of Hg 2+ concentration from 0.2 to 3 ppm, with a low detection limit of 0.05 ppm.

Application study of RGB color extraction in water toxicity detection

In this work, a colorimetric biosensor based on the rapid color change of Escherichia coli DH 5α (E. coli) and p-benzoquinone (BQ) was introduced to evaluate water toxicity. Here, dark brown quinhydroquinone (QHQ) was obtained from the reaction between E. coli and BQ. The inhibition ratios were calculated by RGB (red, green, blue) values of samples or oxidation current of hydroquinone (HQ). Here, RGB technology was used for biotoxicity assessment for the first time. The results suggested that the biosensor-based RGB has an obvious dose-dependent response. The IC20 values of Hg2+ and Cu2+ obtained based on RGB values were 1.0 and 1.5 mg L-1, respectively. This biosensor can be used to detect quickly toxicity of the Cu2+ and Hg2+ in water without complicated operation steps. Therefore, the biosensor has potential application value in the field of water toxicity detection.

Enhancing the sensitivity of water toxicity detection based on suspended Shewanella oneidensis MR-1 by reversing extracellular electron transfer direction.

Water toxicity detection is of great significance to ensure the safety of water supply. With suspended electrochemically active bacteria (EAB) as the sensing element, a novel microbial electrochemical sensor (MES) has recently been reported for the real-time detection of water toxicity, but its practical applications need to further improve the sensitivity. Extracellular electron transfer (EET) is an important factor affecting MES performance. In the study, the EET of suspended EAB-based MES was optimized to further enhance the sensitivity. Firstly, by using a model EAB stain Shewanella oneidensis MR-1, it was revealed that the sensitivity was increased at most 2.7 times with inward EET (i.e., cathodic polarization). Then, a novel conjecture based on electron transfer and energy fluxes was proposed and testified to explain this phenomenon. Finally, three key operating parameters of inward EET were orthogonally optimized. The optimized parameters of inward EET included a potential of - 0.5V, a cell density of 1.8 × 108CFU/mL, and an electron acceptor concentration of 15mM.

A bio-electrochemical sensor based on suspended Shewanella oneidensis MR-1 for the sensitive assessment of water biotoxicity

Water quality monitoring is important to ensure the safety of water supply. With electrochemically active bacteria (EAB) as the key element, bio-electrochemical system (BES) based biosensors are capable to detect water biotoxicity by measuring bioelectricity directly. Traditional BES biosensors relay on mature EAB biofilms. However, due to the self-protective mechanisms of biofilms, the sensitivity of BES biosensors is relatively low, and the detection limit of common pollutants was basically more than 1.0 mg/L. To solve this problem, a BES biosensor based on suspended Shewanella oneidensis MR-1 (S-BES biosensor for short) was established and was used for water biotoxicity detection. The inhibition ratio of S-BES biosensors currents achieved 11.3 % ± 1.6 %–16.7 % ± 0.7 % after 0.1 mg/L heavy metals or organic pollutants toxic shocks. Comparing with traditional BES biosensors, S-BES biosensors exhibited much higher sensitivity in water toxicity detection (about 30 times), showing a great prospect in source water toxicity monitoring. The mechanism of the enhanced sensitivity was further revealed, and it was mainly attributed to the relatively low resistance of suspended bacteria to toxic pollutants.

Colorimetric and Electrochemical Dual-Signal Method for Water Toxicity Detection Based on Escherichia coli and p-Benzoquinone.

The development of simple and rapid toxicity detection methods has important practical significance. In this work, a dual-signal method with colorimetric and electrochemical properties for water toxicity detection was proposed for the first time based on a rapid color reaction between Escherichia coli (E. coli) and p-benzoquinone (BQ). Here, E. coli was used as a biocatalyst and BQ was used as a mediator. An IC50 value of 0.75 mg L-1 for Cu2+ was obtained using a two-step electrochemical detection method. Strikingly, toxicity could also be estimated visually by the naked eye, and the minimum detection limit was 3.2 mg L-1 for Cu2+. The dual-signal toxicity detection method extends the function of BQ, and the result is more reliable than the traditional single-signal method. This simple and rapid toxicity detection method shows certain application prospects.

Self-powered and reusable microbial fuel cell biosensor for toxicity detection in heavy metal polluted water

The development of efficient and high yield techniques and tools are necessary in the current scenario where clean and pollution free water resource are diminishing. In this work, a self-powered and reusable single chambered cylindrical microbial fuel cell (MFC) was developed for toxicity detection in water containing heavy metal ions. The bio-sensing ability of electroactive microbial consortia isolated from industrial wastewater was investigated towards four model heavy metal contaminants (Copper (Cu2+), Chromium (Cr6+), Zinc (Zn2+) and Nickel (Ni2+)). Their inhibition ratio of 5 mg Cu2+, 10 mg Cu2+, 20 mg Cu2+ was found 5.06%, 31.25%, 78.57%, for 5 mg Cr6+, 10 mg Cr6+, 20 mg Cr6+ was found 6.66%, 80.00%, 93.67% for 5 mg Zn2+, 10 mg Zn2+, 20 mg Zn2+ was found 13.33%, 28.57%, 33.07%, and for 5 mg Ni2+, 10 mg Ni2+, 20 mg Ni2+ was found 6.66%, 18.75%, 23.33% respectively. To examine the reusability of biosensor, Sodium acetate (NaAc) was used as key organic substance. After toxic heavy metals shock the fuel cells are fed with Sodium acetate (NaAc) to investigate their recovery cycle time. After recovery of electroactive microbial consortia, the MFC based biosensor shown sensitive towards the Cu2+, Cr6+, Zn2+, and Ni2+ at concentrations above 10 mgL−1. Our experimental result showing that, this type of biosensor is very feasible and potential application in toxicity detection of heavy metals polluted water. This type biosensor device is very cost effective in situ system for water contaminants detection.

Fabrication of a Novel, Cost-Effective Double-Sided Indium Tin Oxide-Based Nanoribbon Electrode and Its Application of Acute Toxicity Detection in Water.

Microelectrode plays a crucial role in developing a rapid biosensor for detecting toxicity in water. In this study, a nanoribbon electrode (NRE) with amplified microelectrode signal was successfully prepared by electrodepositing 2-allylphenol on a double-sided indium tin oxide glass. The NRE provided a simple mean for obtaining large steady-state current response. Its advantages were discussed by contrasting the toxicity detection of 3,5-dichlorophenol (DCP) with single microelectrode, microelectrode array, and millimeter electrode as working electrodes in which potassium ferricyanide (K3[Fe(CN)6]) was adopted as a mediator, and Escherichia coli was selected as bioreceptor. At a constant potential of 450 mV, the current reached a steady state within 10 s. The biosensor was constructed using the NRE as working electrode, and its feasibility was verified by determining the toxicity of DCP. A 50% inhibitory concentration (IC50) of 3.01 mg/L was obtained by analyzing the current responses of different concentrations of DCP within 1 h. These results exhibited that the proposed method based on the as-prepared NRE was a rapid, sensitive, and cost-effective way for toxicity detection in water.

To Study Microbial Fuel Cell with its Recent Developments

Microbial Fuel Cells (MFCs) are the special devices which are been used to produce electricity by anaerobic fermentation of organic as well as inorganic matter from easily metabolized biomass to complex wastewater using microbes as biocatalysts. Microbial Fuel Cell (MFC) is a bio-electrochemical catalytic activity of microbes to produce electricity from the oxidation of organic, substrates under natural condition. There is an increasing interest in photosynthetic MFCs designed to harness Earth's most abundant and promising energy source. Despite their MFCs havent yet successfully translated into commercial applications because they demonstrate persistent performance limitations and bottlenecks associated with scaling up. micro scale MFCs have received attention as a singular platform for various applications like powering small portable electronic elements in remote locations, fundamental studies of microorganisms, screening bacterial strains, toxicity detection in water. MFC is a great technology which can be used in the Modern World for generation of electricity and concomitant wastewater treatmentt.

An unexpected discovery of 1,4-benzoquinone as a lipophilic mediator for toxicity detection in water.

Since most toxicological risk assessments are based on individual single-species tests, there is uncertainty in extrapolating these results to ecosystem assessments. Herein, we successfully developed a mediated microbial electrochemical biosensor with mixed microorganisms for toxicity detection by microelectrode array (MEA). In order to fully mobilize all the mixed microorganisms to participate in electron transfer to amplify the current signal, 1,4-benzoquinone (BQ) was used as the lipophilic mediator to mediate the intracellular metabolic activities. Hydrophilic K3[Fe(CN)6] was employed as an extracellular electron acceptor to transport electrons from hydroquinone (HQ) to the working electrode. Under the optimal conditions of 50 mM phosphate buffer solution (PBS), 0.4 mM BQ, 10 mM K3[Fe(CN)6] and OD600 = 0.5 bacteria concentration, the half-maximal inhibitory concentration (IC50) values measured with the composite-mediated respiration (CM-RES) of BQ-K3[Fe(CN)6] for Cu2+, Cd2+ and Zn2+ were 5.95, 7.12 and 8.86 mg L-1, respectively. IC50 values obtained with the single mediator K3[Fe(CN)6] were 2.34, 5.88 and 2.42 mg L-1 for the same samples. The results indicate that the biosensor with the single mediator K3[Fe(CN)6] had higher sensitivity to heavy metal ions than the biosensor with composite mediators. After verification, we found that the addition of BQ cannot amplify the current. The IC50 value of 0.89 mg L-1 for BQ was obtained using K3[Fe(CN)6] as the single mediator. This suggests that BQ is highly toxic, which explained why the sensitivity of the biosensor with the combined mediator BQ-K3[Fe(CN)6] was lower than that of the biosensor with the single mediator K3[Fe(CN)6]. At the same time, this also implies that toxicity itself cannot be ignored when it is used as an electronic mediator in a mediated microbial electrochemical biosensor.

Preparation, performance, and application of a stable, sensitive and cost-effective microelectrode array

The development of rapid toxicity detection technology has higher requirements for electrode. In this work, a stable, sensitive and cost-effective microelectrode array (MEA) was successfully prepared manually. The advantage of the as-prepared MEA was discussed by means of detecting toxicity of 3,5-Dichlorophenol (3,5-DCP) by contrasting with bulk electrode and single microelectrode, in which mixed microorganisms were selected as biocatalyst, and K3[Fe(CN)6] was adopted as electron mediator. The current reached a stable state in 10 s under the constant potential of 450 mV. The feasibility of rapid detection of toxicity of formaldehyde with the MEA was further verified. The current responses were analyzed over formaldehyde of the final concentrations varied from 0.0036% to 1.0%, and the traditional parameter of 50% inhibitory concentration (IC50) of 0.11% was obtained within 1 h. In brief, the as-prepared MEA has high sensitivity, good stability, strong anti-interference, and well corrosion resistance. It shows a very large application prospects in toxicity detection in water.

Bioelectrochemical biosensor for water toxicity detection: generation of dual signals for electrochemical assay confirmation

Toxicity assessment of water is of great important to the safety of human health and to social security because of more and more toxic compounds that are spilled into the aquatic environment. Therefore, the development of fast and reliable toxicity assessment methods is of great interest and attracts much attention. In this study, by using the electrochemical activity of Shewanella oneidensis MR-1 cells as the toxicity indicator, 3,5-dichlorophenol (DCP) as the model toxic compound, a new biosensor for water toxicity assessment was developed. Strikingly, the presence of DCP in the water significantly inhibited the maximum current output of the S. oneidensis MR-1 in a three-electrode system and also retarded the current evolution by the cells. Under the optimized conditions, the maximum current output of the biosensor was proportional to the concentration of DCP up to 30mg/L. The half maximal inhibitory concentration of DCP determined by this biosensor is about 14.5mg/L. Furthermore, simultaneous monitoring of the retarded time (Δt) for current generation allowed the identification of another biosensor signal in response to DCP which could be employed to verify the electrochemical result by dual confirmation. Thus, the present study has provided a reliable and promising approach for water quality assessment and risk warning of water toxicity.

New applications of genetically modified Pseudomonas aeruginosa for toxicity detection in water

A novel mediator-free method based on genetically modified bacteria was developed for detecting water toxicity, where genetically modified Pseudomonas aeruginosa (GM P. aeruginosa) was selected as the biosensor strain and pyocyanin (PYO) produced by this strain was used as the indicator. The toxicity response of GM P. aeruginosa to 3, 5-dichlorophenol (3, 5-DCP) was measured electrochemically and spectroscopically, and the half maximal inhibitory concentration (IC50) of 3, 5-DCP was determined to be 15.1 mg/L. Strikingly, the toxicity of sample solution with 3, 5-DCP could also be estimated visually by naked eyes at a concentration as low as 10 mg/L. The present study provided a convenient, sensitive and cost-effective method for water toxicity detection, and extended biosensing application of the genetically modified bacterium.

Toxicity detection in water containing heavy metal ions with a self-powered microbial fuel cell-based biosensor

In this work, a self-powered microbial fuel cell (MFC)-based biosensor was developed for detecting toxicity in water containing heavy metal ions. Experimental conditions containing concentration of potassium ferricyanide, load resistor and glucose concentration were optimized. Six heavy metal ions (2mg/L, Cu2+, Hg2+, Zn2+, Cd2+, Pb2+ and Cr3+) were tested by this biosensor and the inhibition ratios obtained were 12.56%, 13.99%, 8.81%, 9.29%, 5.59% and 1.95%, respectively. The inhibition ratios of 28.13% was also obtained for detecting the laboratory wastewater containing several heavy metal ions. The experimental results exhibited the feasibility and potential of the self-powered biosensor in detecting toxicities in water containing heavy metal ions.

Microscale microbial fuel cells: Advances and challenges.

The next generation of sustainable energy could come from microorganisms; evidence that it can be seen with the given rise of Electromicrobiology, the study of microorganisms' electrical properties. Many recent advances in electromicrobiology stem from studying microbial fuel cells (MFCs), which are gaining acceptance as a future alternative "green" energy technology and energy-efficient wastewater treatment method. MFCs are powered by living microorganisms with clean and sustainable features; they efficiently catalyse the degradation of a broad range of organic substrates under natural conditions. There is also increasing interest in photosynthetic MFCs designed to harness Earth's most abundant and promising energy source (solar irradiation). Despite their vast potential and promise, however, MFCs and photosynthetic MFCs have not yet successfully translated into commercial applications because they demonstrate persistent performance limitations and bottlenecks associated with scaling up. Instead, microscale MFCs have received increasing attention as a unique platform for various applications such as powering small portable electronic elements in remote locations, performing fundamental studies of microorganisms, screening bacterial strains, and toxicity detection in water. Furthermore, the stacking of miniaturized MFCs has been demonstrated to offer larger power densities than a single macroscale MFC in terms of scaling up. In this overview, we discuss recent achievements in microscale MFCs as well as their potential applications. Further scientific and technological challenges are also reviewed.

A Novel Cell-Based Hybrid Acoustic Wave Biosensor with Impedimetric Sensing Capabilities

A novel multiparametric biosensor system based on living cells will be presented. The biosensor system includes two biosensing techniques on a single device: resonant frequency measurements and electric cell-substrate impedance sensing (ECIS). The multiparametric sensor system is based on the innovative use of the upper electrode of a quartz crystal microbalance (QCM) resonator as working electrode for the ECIS technique. The QCM acoustic wave sensor consists of a thin AT-cut quartz substrate with two gold electrodes on opposite sides. For integration of the QCM with the ECIS technique a semicircular counter electrode was fabricated near the upper electrode on the same side of the quartz crystal. Bovine aortic endothelial live cells (BAECs) were successfully cultured on this hybrid biosensor. Finite element modeling of the bulk acoustic wave resonator using COMSOL simulations was performed. Simultaneous gravimetric and impedimetric measurements performed over a period of time on the same cell culture were conducted to validate the device's sensitivity. The time necessary for the BAEC cells to attach and form a compact monolayer on the biosensor was 35∼45 minutes for 1.5 × 104 cells/cm2 BAECs; 60 minutes for 2.0 × 104 cells/cm2 BAECs; 70 minutes for 3.0 × 104 cells/cm2 BAECs; and 100 minutes for 5.0 × 104 cells/cm2 BAECs. It was demonstrated that this time is the same for both gravimetric and impedimetric measurements. This hybrid biosensor will be employed in the future for water toxicity detection.

Development of a quantitative optical biochip based on a double integrating sphere system that determines absolute photon number in bioluminescent solution: application to quantum yield scale realization

We report a new design of an optical biochip based on a double integrating sphere system to quantify the absolute number of the emitted photons or the total photon flux by a whole cell bioluminescent biosensor, for water toxicity detection, based on genetically engineered Escherichia coli bacteria carrying a recA::luxCDABE promoter-reporter fusion. The new design of the double integrating sphere system does not require any external standard light source for calibration of the tested bioluminescent solution and allows a direct determination of the total photon flux of the bioluminescent solution. In our design, we required that the two spheres are symmetric (have the same radius and reflectance) with a surface area larger than the cut cap area between the spheres.

Modeling and measurement of a whole-cell bioluminescent biosensor based on a single photon avalanche diode

Whole-cell biosensors are potential candidates for on-line and in situ environmental monitoring. In this work we present a new design of a whole-cell bioluminescence biosensor for water toxicity detection, based on genetically engineered Escherichia coli bacteria, carrying a recA::luxCDABE promoter–reporter fusion. Sensitive optical detection is achieved using a single photon avalanche photodiode (SPAD) working in the Geiger mode. The present work describes a simple mathematical model for the kinetic process of the bioluminescence based SOS toxin response of E. coli bacteria. We find that initially the bioluminescence signal depends on the time square and we show that the spectral intensity of the bioluminescence signal is inverse proportional to the frequency. We get excellent agreement between the theoretical model and the measured light signal. Furthermore, we present experimental results of the bioluminescent signal measurement using a SPAD and a photomultiplier, and demonstrate improvement of the measurement by applying a matched digital filter. Low intensity bioluminescence signals were measured after the whole-cell sensors were exposed to various toxicant concentrations (5, 15 and 20 ppm).

Mathematical model of whole cell based bio-chip: An electrochemical biosensor for water toxicity detection

Whole cell biosensors, which have been genetically engineered to respond to environmental stress, trigger a sequence of processes, which leads to generation of electrical current. This work presents a mathematical model describing the kinetic properties of the bacterial enzymatic reactions in response to toxic chemicals, and the resulting electro-active molecule diffusion to the electrode in a miniaturized electrochemical cell. The model characterizes the generated electrical current as a function of bacteria and toxicant concentrations, electrochemical cell dimensions and electrode dimensions. A model was framed for a 100 nL spherical electrochemical cell. Its performance was simulated and compared to experimental data. This simulation results agreed well with the measured data and therefore it should be useful in predicting current variations in similar systems with different geometries, materials and biological components.