An eco-designed paper-based algal biosensor for nanoformulated herbicide optical detection

Herbicide detection: A review of enzyme- and cell-based biosensors

Herbicides are the most widely used class of pesticides in the world. Their intensive use raises the question of their harmfulness to the environment and human health. These pollutants need to be detected at low concentrations, especially in water samples. Commonly accepted analytical techniques (HPLC-MS, GC-MS, ELISA tests) are available, but these highly sensitive and time-consuming techniques suffer from high cost and from the need for bulky equipment, user training and sample pre-treatment. Biosensors can be used as complementary early-warning systems that are less sensitive and less selective. On the other hand, they are rapid, inexpensive, easy-to-handle and allow direct detection of the sample, on-site, without any further step other than dilution. This review focuses on enzyme- and cell- (or subcellular elements) based biosensors. Different enzymes (such as tyrosinase or peroxidase) whose activity is inhibited by herbicides are presented. Photosynthetic cells such as algae or cyanobacteria are also reported, as well as subcellular elements (thylakoids, chloroplasts). Atrazine, diuron, 2,4-D and glyphosate appear as the most frequently detected herbicides, using amperometry or optical transduction (mainly based on chlorophyll fluorescence). The recent new WSSA/HRAC classification of herbicides is also included in the review.

Extremozyme-Based Biosensors for Environmental Pollution Monitoring: Recent Developments

Extremozymes combine high specificity and sensitivity with the ability to withstand extreme operational conditions. This work presents an overview of extremozymes that show potential for environmental monitoring devices and outlines the latest advances in biosensors utilizing these unique molecules. The characteristics of various extremozymes described so far are presented, underlining their stability and operational conditions that make them attractive for biosensing. The biosensor design is discussed based on the detection of photosynthesis-inhibiting herbicides as a case study. Several biosensors for the detection of pesticides, heavy metals, and phenols are presented in more detail to highlight interesting substrate specificity, applications or immobilization methods. Compared to mesophilic enzymes, the integration of extremozymes in biosensors faces additional challenges related to lower availability and high production costs. The use of extremozymes in biosensing does not parallel their success in industrial applications. In recent years, the "collection" of recognition elements was enriched by extremozymes with interesting selectivity and by thermostable chimeras. The perspectives for biosensor development are exciting, considering also the progress in genetic editing for the oriented immobilization of enzymes, efficient folding, and better electron transport. Stability, production costs and immobilization at sensing interfaces must be improved to encourage wider applications of extremozymes in biosensors.

Advanced nanopesticides: Advantage and action mechanisms

The use of various chemical substances to control pests, diseases, and weeds in the field is a necessary part of the agricultural development process in every country. While the application of pesticides can improve the quality and yield of crops, plant resistance and the harm caused by pesticide residues to the environment and humans have led to the search for greener and safer pesticide formulations to improve the current situation. In recent years, nanopesticides (NPts) have shown great potential in agriculture due to their high efficiency, low toxicity, targeting, resistance, and controlled slow release demonstrated in the experimental stage. Commonly used approaches to prepare NPts include the use of nanoscale metal materials as active ingredients (AI) (ingredients that can play a role in insecticide, sterilization and weeding) or the construction of carriers based on commonly used pesticides to make them stable in nano-sized form. This paper systematically summarizes the advantages and effects of NPts over conventional pesticides, analyzes the formation and functions of NPts in terms of structure, AI, and additives, and describes the mechanism of action of NPts. Despite the feasibility of NPts use, there is not enough comprehensive research on NPts, which must be supplemented by more experiments in terms of biotoxicology and ecological effects to provide strong support for NPts application.

Road Map of Semiconductor Metal-Oxide-Based Sensors: A Review

Identifying disease biomarkers and detecting hazardous, explosive, flammable, and polluting gases and chemicals with extremely sensitive and selective sensor devices remains a challenging and time-consuming research challenge. Due to their exceptional characteristics, semiconducting metal oxides (SMOxs) have received a lot of attention in terms of the development of various types of sensors in recent years. The key performance indicators of SMOx-based sensors are their sensitivity, selectivity, recovery time, and steady response over time. SMOx-based sensors are discussed in this review based on their different properties. Surface properties of the functional material, such as its (nano)structure, morphology, and crystallinity, greatly influence sensor performance. A few examples of the complicated and poorly understood processes involved in SMOx sensing systems are adsorption and chemisorption, charge transfers, and oxygen migration. The future prospects of SMOx-based gas sensors, chemical sensors, and biological sensors are also discussed.

An All-Green Photo-Electrochemical Biosensor Using Microalgae Immobilized on Eco-Designed Lignin-Based Screen-Printed Electrodes to Detect Sustainable Nanoherbicides

Herein, a novel completely green biosensor was designed exploiting both the biological and instrumental components made of eco-friendly materials for the detection of herbicides encapsulated into biodegradable nanoparticles for a sustainable agriculture. Similar nanocarriers, indeed, can deliver herbicides to the correct location, reducing the amount of active chemicals deposited in the plant, impacting the agricultural and food industries less. However, handling measurements of nanoherbicides is crucial to provide comprehensive information about their status in the agricultural fields to support farmers in decision-making. In detail, whole cells of the unicellular green photosynthetic alga Chlamydomonas reinhardtii UV180 mutant were immobilized by a green protocol on carbonized lignin screen-printed electrodes and integrated into a photo-electrochemical transductor for the detection of nanoformulated atrazine. Specifically, atrazine encapsulated into zein and chitosan doped poly-ε-caprolactone nanoparticles (atrazine-zein and atrazine-PCL-Ch) were analyzed following the current signals at a fixed applied potential of 0.8 V, in a range between 0.1 and 5 µM, indicating a linear relationship in the measured dose-response curves and a detection limit of 0.9 and 1.1 nM, respectively. Interference studies resulted in no interference from 10 ppb bisphenol A, 1 ppb paraoxon, 100 ppb arsenic, 20 ppb copper, 5 ppb cadmium, and 10 ppb lead at safety limits. Finally, no matrix effect was observed on the biosensor response from wastewater samples and satisfactory recovery values of 106 ± 8% and 93 ± 7% were obtained for atrazine-zein and atrazine-PCL-Ch, respectively. A working stability of 10 h was achieved.

A systematic review of the toxic effects of a nanopesticide on non-target organisms: Estimation of protective concentrations using a species sensitivity distribution (SSD) approach - The case of atrazine

Nanopesticides, such as nanoencapsulated atrazine (nATZ), have been studied and developed as eco-friendly alternatives to control weeds in fields, requiring lower doses. This review contains a historical and systematic literature review about the toxicity of nATZ to non-target species. In addition, the study establishes protective concentrations for non-target organisms through a species sensitivity distribution (SSD) approach. Through the systematic search, we identified 3197 publications. Of these, 14 studies addressed "(nano)atrazine's toxicity to non-target organisms". Chronological and geographic data on the publication of articles, characterization of nATZ (type of nanocarrier, size, polydispersity index, zeta potential), experimental design (test species, exposure time, measurements, methodology, tested concentrations), and toxic effects are summarized and discussed. The data indicate that cell and algal models do not show sensitivity to nATZ, while many terrestrial and aquatic invertebrates, aquatic vertebrates, microorganisms, and plants have high sensitivity to nAZT. The SSD results indicated that D. similis is the most sensitive species to nATZ, followed by C. elegans, E. crypticus, and P. subcapitata. However, the limitations in terms of the number of species and endpoints available to elaborate the SSD reflect gaps in knowledge of the effects of nATZ on different ecosystems.

Sol-Gel Immobilized Optical Microalgal Biosensor for Monitoring Cd, Cu and Zn Bioavailability in Freshwater

While analytical measurements provide the quantitative estimation of the total amount of metals present in a sample, they do not reflect the truly bioavailable fraction of metal which reflects the adverse biological effect. Hence the development of monitoring tools for detecting bioavailable toxic metals has become a priority in environmental monitoring activities. An optical whole-cell biosensor was constructed using the microalga Scenedesmus subspicatus MM1 immobilizing in inorganic silica hydrogels using the sol-gel technique to detect bioavailable Cadmium (Cd²⁺), Copper (Cu²⁺) and Zinc (Zn⁺) in freshwater. Conditions for optimum biosensor performance have been established regarding effective pH range, cell density, exposure time, and storage stability. The optimum response for the biosensor was dependent on the pH of the matrix, cell concentration and exposure time were derived. The biosensor was operational for four weeks. The limit of detection for the algal biosensor was determined as 9.0 × 10^-1, 9.1 × 10^-1, and 8.8 × 10^-1 mg/L for Cd, Cu and Zn, respectively. Whole-cell cell biosensor will be highly useful since it comprises a single microalgal species able to detect the bioavailable content of Cd²⁺, Cu²⁺, and Zn²⁺ in freshwater.

Optical Biosensors and Their Applications for the Detection of Water Pollutants

The correct detection and quantification of pollutants in water is key to regulating their presence in the environment. Biosensors offer several advantages, such as minimal sample preparation, short measurement times, high specificity and sensibility and low detection limits. The purpose of this review is to explore the different types of optical biosensors, focusing on their biological elements and their principle of operation, as well as recent applications in the detection of pollutants in water. According to our literature review, 33% of the publications used fluorescence-based biosensors, followed by surface plasmon resonance (SPR) with 28%. So far, SPR biosensors have achieved the best results in terms of detection limits. Although less common (22%), interferometers and resonators (4%) are also highly promising due to the low detection limits that can be reached using these techniques. In terms of biological recognition elements, 43% of the published works focused on antibodies due to their high affinity and stability, although they could be replaced with molecularly imprinted polymers. This review offers a unique compilation of the most recent work in the specific area of optical biosensing for water monitoring, focusing on both the biological element and the transducer used, as well as the type of target contaminant. Recent technological advances are discussed.

Highly selective molecularly imprinted-electrochemiluminescence sensor based on perovskite/Ru(bpy)32+ for simazine detection in aquatic products

A novel molecularly imprinted electrochemiluminescence (MIECL) sensor based on the luminescence of molecularly imprinted polymer-perovskite (MIP-CsPbBr₃) layer and Ru(bpy)₃²⁺ was fabricated for simazine detection. MIP-CsPbBr₃ layers were immobilized onto the surface of glassy carbon electrode as the capture and signal amplification probe, and Ru(bpy)₃²⁺ and co-reactant tripropylamine exhibited stronger electrochemiluminescence (ECL) emission. Under optimal conditions, the ECL signal of the MIECL sensor was linearly quenched, with the logarithm of simazine concentration ranging from 0.1 μg/L to 500.0 μg/L, correlation coefficient of 0.9947, and limit of detection of 0.06 μg/L. The practicality of the developed MIECL sensor method for simazine determination in aquatic samples was validated. Excellent recoveries of 86.5 %-103.9 % with relative standard deviation below 1.6 % were obtained for fish and shrimp samples at three different spiked concentrations. The MIECL sensor exhibited excellent selectivity, sensitivity, reproducibility, accuracy, and precision for simazine determination in actual aquatic samples.

Optical sensing techniques for rapid detection of agrochemicals: Strategies, challenges, and perspectives

In recent years, the irrational use of agrochemicals has caused great harm to the environment and public health. Along with the rapid development of optical technology and nanotechnology, the research of optical sensing methods in agrochemical detection has been developed rapidly owing to its advantages of simplicity, fast response, and cost-effectiveness. In this review, the strategies of employing optical systems based on colorimetric sensor, fluorescence, chemiluminescence, terahertz spectroscopy, surface plasmon resonance, and surface-enhanced Raman spectroscopy for sensing agrochemicals were summarized. In addition, the challenges in the practical application of optical sensing technologies for agrochemical detection were discussed in-depth, and potential future trends and prospects of these techniques were addressed. A variety of nanomaterials have been developed for enhancing the sensitivity of optical sensing systems. The optical properties of nanomaterials are governed by their size, shape, and chemical structure. Although each optical sensing system holds its advantages, there are still many challenges that need to be overcome in practical applications. With the continuous developments in novel functional nanomaterials, sample preparation methods, and spectral processing algorithms, optical sensors are expected to have powerful potential for rapid testing of agrochemicals in the environment and foods.

The Impact of Cameraria ohridella (Lepidoptera, Gracillariidae) on the State of Aesculus hippocastanum Photosynthetic Apparatus in the Urban Environment

The paper presents the results on resistance of Aesculus hippocastanum Linnaeus, 1753 trees to Cameraria ohridella Deschka & Dimić, 1986 (Lepidoptera, Gracillariidae) impact under conditions of a modern urban environment on the example of Dnipro city as the largest industrial city in Ukraine. Field experiments were conducted in all park areas of the city, which allowed covering the full gradient of the existing urban environment and considered the different degrees of the tree settlement by the invasive insect species. The research of the impact of C. ohridella caterpillars’ vital activity on the photosynthetic apparatus state was carried out by applying a chlorophyll fluorescence induction technique. Diagnosis of photosynthetic dysfunction of fresh Ae. hippocastanum leaves was conducted using a portable “Floratest” fluorometer manufactured in Ukraine. Interpretation of the obtained Kautsky curves showed that significant changes in their critical parameters associated with the degree of leaf damage by C. ohridella caterpillars were not detected. The influence of tree growth site conditions on the following 4 main indicators of chlorophyll fluorescence induction was established: the initial value of fluorescence induction after irradiation; the value of “plateau” fluorescence induction; the maximum value of fluorescence induction; the stationary value of fluorescence induction after light adaptation of the plant leaf. It was found that the efficiency coefficients of photochemical processes in Ae. hippocastanum trees growing in low terrain levels differed significantly, which can probably be interpreted as their response to the specific characteristics of the urban environment.

A Proof-of-Concept Electrochemical Cytosensor Based on Chlamydomonas reinhardtii Functionalized Carbon Black Screen-Printed Electrodes: Detection of Escherichia coli in Wastewater as a Case Study

Herein, we report a proof-of-concept algal cytosensor for the electrochemical quantification of bacteria in wastewater, exploiting the green photosynthetic alga Chlamydomonas reinhardtii immobilized on carbon black (CB) nanomodified screen-printed electrodes. The CB nanoparticles are used as nanomodifiers, as they are able to sense the oxygen produced by the algae and thus the current increases when algae are exposed to increasing concentrations of bacteria. The sensor was tested on both standard solutions and real wastewater samples for the detection Escherichia coli in a linear range of response from 100 to 2000 CFU/100 mL, showing a limit of detection of 92 CFU/100 mL, in agreement with the maximum E. coli concentration established by the Italian law for wastewater (less than 5000 CFU/100 mL). This bacterium was exploited as a case study target of the algal cytosensor to demonstrate its ability as an early warning analytical system to signal heavy loads of pathogens in waters leaving the wastewater treatment plants. Indeed, the cytosensor is not selective towards E. coli but it is capable of sensing all the bacteria that induce the algae oxygen evolution by exploiting the effect of their interaction. Other known toxicants, commonly present in wastewater, were also analyzed to test the cytosensor selectivity, with any significant effect, apart from atrazine, which is a specific target of the D1 protein of the Chlamydomonas photosystem II. However, the latter can also be detected by chlorophyll fluorescence simultaneously to the amperometric measurements. The matrix effect was evaluated, and the recovery values were calculated as 105 ± 8, 83 ± 7, and 88 ± 7% for 1000 CFU/100 mL of E. coli in Lignano, San Giorgio, and Pescara wastewater samples, respectively.

Detection and remediation of pollutants to maintain ecosustainability employing nanotechnology: A review

Environmental deterioration due to anthropogenic activities is a threat to sustainable, clean and green environment. Accumulation of hazardous chemicals pollutes soil, water and air and thus significantly affects all the ecosystems. This article highlight the challenges associated with various conventional techniques such as filtration, absorption, flocculation, coagulation, chromatographic and mass spectroscopic techniques. Environmental nanotechnology has provided an innovative frontier to combat the aforesaid issues of sustainable environment by reducing the non-requisite use of raw materials, electricity, excessive use of agrochemicals and release of industrial effluents into water bodies. Various nanotechnology based approaches including surface enhance scattering, surface plasmon resonance; and distinct types of nanoparticles like silver, silicon oxide and zinc oxide have contributed significantly in detection of environmental pollutants. Biosensing technology has also gained significant attention for detection and remediation of pollutants. Furthermore, nanoparticles of gold, ferric oxide and manganese oxide have been used for the on-site remediation of antibiotics, organic dyes, pesticides, and heavy metals. Recently, green nanomaterials have been given more attention to address toxicity issues of chemically synthesized nanomaterials. Hence, nanotechnology has provided a platform with tremendous applications to have sustainable environment for present as well as future generations. This review article will help to understand the fundamentals for achieving the goals of sustainable development, and healthy environment.

Recent advances of environmental pollutants detection via paper-based sensing strategy

Paper has become one of the most promising substrates for building low-cost and powerful sensing platforms due to its self-pumping ability and compatibility with multiple patterning methods. Paper-based sensors have been greatly developed in the field of environmental monitoring. In this review, we introduced the research and application of paper-based sensors in environmental monitoring, focusing on the deposition and patterning methods of building paper-based sensors, and summarized the applications of detecting environmental pollutants, including metal ions, anions, explosives, neurotoxins, volatile organic compounds, and small molecules. In addition, the development prospects and challenges of promoting paper-based sensors are also discussed. The current review will provide references for the construction of portable paper-based sensors, and has implications for the field of on-site real-time detection of the environment.

Nanobioengineered Sensing Technologies Based on Cellulose Matrices for Detection of Small Molecules, Macromolecules, and Cells

Recent advancement has been accomplished in the field of biosensors through the modification of cellulose as a nano-engineered matrix material. To date, various techniques have been reported to develop cellulose-based matrices for fabricating different types of biosensors. Trends of involving cellulosic materials in paper-based multiplexing devices and microfluidic analytical technologies have increased because of their disposable, portable, biodegradable properties and cost-effectiveness. Cellulose also has potential in the development of cytosensors because of its various unique properties including biocompatibility. Such cellulose-based sensing devices are also being commercialized for various biomedical diagnostics in recent years and have also been considered as a method of choice in clinical laboratories and personalized diagnosis. In this paper, we have discussed the engineering aspects of cellulose-based sensors that have been reported where such matrices have been used to develop various analytical modules for the detection of small molecules, metal ions, macromolecules, and cells present in a diverse range of samples. Additionally, the developed cellulose-based biosensors and related analytical devices have been comprehensively described in tables with details of the sensing molecule, readout system, sensor configuration, response time, real sample, and their analytical performances.

A dual electro-optical biosensor based on Chlamydomonas reinhardtii immobilised on paper-based nanomodified screen-printed electrodes for herbicide monitoring

The indiscriminate use of herbicides in agriculture contributes to soil and water pollution, with important endangering consequences on the ecosystems. Among the available analytical systems, algal biosensors have demonstrated to be valid tools thanks to their high sensitivity, cost-effectiveness, and eco-design. Herein, we report the development of a dual electro-optical biosensor for herbicide monitoring, based on Chlamydomonas reinhardtii whole cells immobilised on paper-based screen-printed electrodes modified with carbon black nanomaterials. To this aim, a systematic study was performed for the selection and characterisation of a collection among 28 different genetic variants of the alga with difference response behaviour towards diverse herbicide classes. Thus, CC125 strain was exploited as case study for the study of the analytical parameters. The biosensor was tested in standard solutions and real samples, providing high sensitivity (detection limit in the pico/nanomolar), high repeatability (RSD of 5% with n = 100), long lasting working (10 h) and storage stability (3 weeks), any interference in the presence of heavy metals and insecticides, and low matrix effect in drinking water and moderate effect in surface one.

Effect of Cameraria ohridella feeding on Aesculus hippocastanum photosynthesis

The complex of invasive species of phytophagous insects that can adapt to novel living conditions is constantly increasing. The ecological effect of their vital activity in the new environment is almost impossible to predict. As a result, invasions undesirable in the economic sense are often observed. The horse -chestnut leaf miner (Cameraria ohridella Deschka & Dimič, 1986, Gracillariidae) is one of these problematic invader species in the introduced range of the horse chestnut (Aesculus hippocastanum (Linnaeus, 1753), Sapindaceae). We studied the effect of C. ohridella on the state of the photosynthetic apparatus in Ae. hippocastanum leaves. Photosynthesis is the one of the processes most vulnerable to stress factors, so information about the state of photosynthetic apparatus in a plant under the influence of phytophage feeding obtained with fluorescence analysis can be significant. The feeding effect of C. ohridella caterpillars on the functional state and activity of Ae. hippocastanum photosynthetic apparatus was studied. We studied critical parameters of chlorophyll fluorescence induction reflecting the effect of a single C. ohridella generation (feeding the caterpillar for the five stages of this species’ development) on the functional links of the photosystem II in Ae. hippocastanum leaves. The data obtained show a decrease in PS II quantum efficiency (inhibition of photosynthetic activity) in the leaves from different parts of the crown; it suggests the destructive effect of C. ohridella caterpillar feeding on Ae. hippocastanum photosynthetic apparatus. Values of all key parameters of chlorophyll fluorescence indication evidence inhibition of photophysical and photochemical processes of photosynthesis and impaired coherence of Calvin cycle reactions. Study of the feeding effect of C. ohridella caterpillars on the efficiency of the main enzyme in the Calvin cycle (which closely correlates with the coefficient of fluorescence induction that characterizes the efficiency of dark photosynthetic processes) showed a significant decrease in its activity in the leaves of both the illuminated and shaded parts of the crown. Our study has shown that the method of chlorophyll fluorescence induction allows one to determine the general state of a plant in an express regime by evaluating the main process of plant life as photosynthesis. Analysis of chlorophyll fluorescence parameters is a powerful and effective tool for determining the effect of phytophages on the plant body. The obtained data allow us to apply the method of analyzing chlorophyll fluorescence induction in practice to establish the physiological state of tree flora in forests and garden farms.

An Overview on Recent Progress of Metal Oxide/Graphene/CNTs-Based Nanobiosensors

Nanobiosensors are convenient, practical, and sensitive analyzers that detect chemical and biological agents and convert the results into meaningful data between a biologically active molecule and a recognition element immobilized on the surface of the signal transducer by a physicochemical detector. Due to their fast, accurate and reliable operating characteristics, nanobiosensors are widely used in clinical and nonclinical applications, bedside testing, medical textile industry, environmental monitoring, food safety, etc. They play an important role in such critical applications. Therefore, the design of the biosensing interface is essential in determining the performance of the nanobiosensor. The unique chemical and physical properties of nanomaterials have paved the way for new and improved sensing devices in biosensors. The growing demand for devices with improved sensing and selectivity capability, short response time, lower limit of detection, and low cost causes novel investigations on nanobiomaterials to be used as biosensor scaffolds. Among all other nanomaterials, studies on developing nanobiosensors based on metal oxide nanostructures, graphene and its derivatives, carbon nanotubes, and the widespread use of these nanomaterials as a hybrid structure have recently attracted attention. Nanohybrid structures created by combining these nanostructures will directly meet the future biosensors' needs with their high electrocatalytic activities. This review addressed the recent developments on these nanomaterials and their derivatives, and their use as biosensor scaffolds. We reviewed these popular nanomaterials by evaluating them with comparative studies, tables, and charts.

Metal-Oxide Based Nanomaterials: Synthesis, Characterization and Their Applications in Electrical and Electrochemical Sensors

Pure, mixed and doped metal oxides (MOX) have attracted great interest for the development of electrical and electrochemical sensors since they are cheaper, faster, easier to operate and capable of online analysis and real-time identification. This review focuses on highly sensitive chemoresistive type sensors based on doped-SnO₂, RhO, ZnO-Ca, Sm_x-CoFe_2−xO₄ semiconductors used to detect toxic gases (H₂, CO, NO₂) and volatile organic compounds (VOCs) (e.g., acetone, ethanol) in monitoring of gaseous markers in the breath of patients with specific pathologies and for environmental pollution control. Interesting results about the monitoring of biochemical substances as dopamine, epinephrine, serotonin and glucose have been also reported using electrochemical sensors based on hybrid MOX nanocomposite modified glassy carbon and screen-printed carbon electrodes. The fundamental sensing mechanisms and commercial limitations of the MOX-based electrical and electrochemical sensors are discussed providing research directions to bridge the existing gap between new sensing concepts and real-world analytical applications.

Physiological mechanisms and phytoremediation potential of the macrophyte Salvinia biloba towards a commercial formulation and an analytical standard of glyphosate

Glyphosate (Gly) is the most widely used herbicide in the world and has broad-spectrum and non-selective activity. Its indiscriminate use hence risks contamination of water bodies and can affect living organisms, especially sensitive or resistant non-target plants. Despite this, studies on physiological mechanisms and Gly remediation in Neotropical aquatic plants remain limited. This study aims to evaluate the physiological mechanisms of the aquatic macrophyte Salvinia biloba on exposure to different concentrations of a Gly commercial formulation (Gly-CF) and a Gly analytical standard (Gly-AS). Furthermore, using square-wave voltammetry (SWV), we determined whether the studied plant could remove Gly from water. Our data suggest that Gly-AS and Gly-CF induce similar physiological responses in S. biloba. However, Gly-CF was more phytotoxic. Depending on the concentration, the two forms of Gly affected the plants, decreasing the chlorophyll a and b contents and the photosystem II (PSII) photochemical activity. The data also revealed that Gly promoted oxidative stress and increased the shikimic acid concentration. At the same time, the plants removed Gly from water, with 100% removal for 1 mg L-1 Gly and above 60% removal for the other concentrations studied. Therefore, our results suggest that S. biloba may be a potential phytoremediation agent for low Gly concentrations, since 1 mg L-1 Gly was completely removed and exhibited low phytotoxicity. This study deepens our scientific understanding of the Gly impact on and the phytoremediation potential of S. biloba.

Fabrication and Characterization of a Novel Herbicide Delivery System with Magnetic Collectability and Its Phytotoxic Effect on Photosystem II of Aquatic Macrophyte

The use of nano- and microparticles as a release system for agrochemicals has been increasing in agricultural sector. However, the production of eco-friendly and smart carriers that can be easily handled in the environment is still a challenge for this technology. In this context, we have developed a biodegradable release system for the herbicide atrazine with magnetic properties. Herein, we investigated the (a) physicochemical properties of the atrazine-loaded magnetic poly(ε-caprolactone) microparticles (MPs:ATZ), (b) in vitro release kinetic profile of the herbicide, and (c) phytotoxicity toward photosynthesis in the aquatic fern Azolla caroliniana. The encapsulation efficiency of the herbicide in the MPs:ATZ was ca. 69%, yielding spherical microparticles with a diameter of ca. 100 μm, a sustained-release profile, and easily manipulated with an external magnetic field. Also, phytotoxicity issues showed that the MPs:ATZ maintained their herbicidal activity via inhibition of PSII, showing lower toxicity compared with the nonencapsulated ATZ at 0.01 and 0.02 μmol·L^-1. Therefore, this technology may conveniently promote a novel magnetic controlled release of the herbicide ATZ (with the potential to be collected from a watercourse) and act as a nutrient boost to the nontarget plant, with good herbicidal activity and reduced risk to the environment.

Portable, Disposable, Paper-Based Microbial Fuel Cell Sensor Utilizing Freeze-Dried Bacteria for In Situ Water Quality Monitoring

Water quality monitoring is becoming an essential part of our lives as increasing human activities continue to spill unknown and unexpected contaminants into our water systems. To ensure the provision of safe and clean water to the public and the ecosystem, the development of rapid and sensitive in situ early warning systems for water toxicity monitoring is crucial. In this work, an entirely paper-based microbial fuel cell sensor utilizing freeze-dried bacteria is demonstrated as a portable and disposable water toxicity sensor. The bacterial cells were preinoculated on the anode reservoir of the device, and they were freeze-dried, making their on-site and on-demand applications possible. Upon rehydration of the bacteria with the water samples, current readings were obtained, and inhibition ratios (IRs) were calculated for different concentrations of formaldehyde as a model toxin. For 0.001, 0.01, and 0.02% of formaldehyde, IRs of 7.88, 16.08, and 23.14% were obtained, respectively. These IRs showed a very good linearity with the formaldehyde concentrations at R ² = 0.995. Additionally, the shelf life of the freeze-dried microbial fuel cell sensor was investigated. Even after 14 days of storage in the desiccator, at 4, and at -20 °C, the performance outputs compared to the new device were all at 96%.

Metal Oxides-Based Semiconductors for Biosensors Applications

The present mini review contains a concessive overview on the recent achievement regarding the implementation of a metal oxide semiconductor (MOS) in biosensors used in biological and environmental systems. The paper explores the pathway of enhancing the sensing characteristics of metal oxides by optimizing various parameters such as synthesis methods, morphology, composition, and structure. Four representative metal oxides (TiO₂, ZnO, SnO₂, and WO₃) are presented based on several aspects: synthesis method, morphology, functionalizing molecules, detection target, and limit of detection (LOD).

Carbon black nanoparticles to sense algae oxygen evolution for herbicides detection: Atrazine as a case study

A novel amperometric algae-based biosensor was developed for the detection of photosynthetic herbicides in river water. The green photosynthetic algae Chlamydomonas reinhardtii was immobilized on carbon black modified screen-printed electrodes, exploiting carbon black as smart nanomaterial to monitor changes in algae oxygen evolution during the photosynthetic process. The decrease of oxygen evolution, occurring in the presence of herbicides, results in a decrease of current signals by means of amperometric measurements, in an analyte concentration dependent manner. Atrazine as case study herbicide was detected in a concentration range of 0.1 and 50 μM, with a linear range from 0.1 to 5 μM and a detection limit of 1 nM. No interference was observed in presence of 100 ppb arsenic, 20 ppb copper, 5 ppb cadmium, 10 ppb lead, 10 ppb bisphenol A, and 1 ppb paraoxon, tested as safety limits. A ~25% matrix effect and satisfactory recovery values of 107 ± 10% and 96 ± 8% were obtained in river water for 3 and 5 μM of atrazine, respectively. Stability studies were also performed obtaining a high working stability up to 10 h and repeatability with an RSD of 1.1% (n = 12), as well as a good storage stability up to 3 weeks.

To evaluate the toxicity of atrazine on the freshwater microalgae Chlorella sp. using sensitive indices indicated by photosynthetic parameters

Atrazine is a widely-applied herbicide used primarily to control weeds, which can persist in the ecosystem and exert potential toxicity to phytoplankton in the aquatic environment. In this study, acute toxicity of atrazine on microalgae Chlorella sp. was investigated with different initial cell densities (1 × 10⁵ and 1 × 10⁶ cells mL^-1) and exposure periods (4 d and 8 d). Both growth rate and photosynthetic parameters of the microalgae in response of atrazine stress were determined to find out the sensitive indices and toxicological mechanisms. Because of the independence of initial cell density as well as the high sensitivity and reliability, the performance index PI_ABS was verified as the most convincing photosynthetic parameter for indicating IC₅₀ of atrazine on Chlorella sp., being superior to the traditional parameters of growth rate and F_V/F_M. The IP amplitude (ΔF_IP, fluorescence amplitude of the I-to-P-rise in the OJIP curve) was another sensitive biomarker to reflect atrazine stress. Results from chlorophyll fluorescence transient revealed that atrazine damaged the photosystem II (PS II) reaction center, suppressed the electron transport at the donor and receptor sides, and acted on the absorption, transfer, and utilization of light energy. Our results provide confirmatory references for understanding the toxicity and mechanisms of atrazine on freshwater microalgae.

Biotechnological Advances in the Design of Algae-Based Biosensors

In addition to their use in biomass production and bioremediation, algae have been extensively exploited in biosensing applications. Algae-based biosensors have demonstrated potential for sensitive, sustainable, and multiplexed detection of analytes of agroenvironmental and security interest. Their advantages include the availability of different algal bioreceptors including whole cells and their photosynthetic subcomponents, their potential to be integrated into dual transduction miniaturized devices, and the opportunity for continuous environmental monitoring. Despite obstacles including limited stability and selectivity, algae-based biosensing is a realistic prospect that has some recent effective applications. Strategic exploitation of cutting-edge technologies including materials science, nanotechnology, microfluidics, and genome editing will help to achieve the full potential of algae-based sensors.