Enzyme inhibition-based biosensors for food safety and environmental monitoring

A Highly Selective Schiff Base Based Chemodosimeter for the Detection of Perfluorooctanoic Acid by Optical Biosensor

A simple imine derivative based sensor (IDP) has been synthesized and characterized by 1 H NMR, 13 C NMR and mass spectral techniques. IDP is more capable of detecting perfluorooctanoic acid (PFOA) in a selective and sensitive manner. The PFOA as a biomarker interacts with IDP and shows "TURN-ON" response by colorimetric and fluorimetric method. Under optimized experimental observations, the selective determination of PFOA using IDP among other competitors as biomolecules has been noticed. The detection limit is 0.31 × 10- 8 mol/L. The practical applications of the IDP is effectively evaluated in human biofluids and water samples.

Electrochemical Biosensors Based on Enzyme Inhibition Effect

Several electrochemical biosensors based on various enzyme inhibition effects have been designed; their laboratory prototypes have been manufactured and thoroughly investigated. It should be noted that such biosensors are adapted to large-scale production technologies. A number of advantages and disadvantages of developed biosensors based on enzyme inhibition has been discussed. It is important that all developed biosensors are not opposite to traditional analytical methods, but complement them. This is an additional system of quick and early warning about the presence of toxic substances in the environment. Such systems can save time and money in emergencies due to the possibility of quick decision-making on local environmental problems. If necessary, more accurate, but time-consuming and expensive traditional methods could be used for further validation and additional research of samples previously tested by biosensors.

Fabrication and application of glutathione biosensing SPCE strips with gold nanoparticle modification

Glutathione (GSH) is a major antioxidant in organisms. An alteration in GSH concentration has been implicated in a number of pathological conditions. Therefore, GSH sensing has become a critical issue. In this study, a disposable strip used for tyrosinase-modified electrochemical testing was fabricated for the detection of GSH levels in vivo. The system is based on tyrosinase as a biorecognition element and a screen-printed carbon electrode (SPCE) as an amperometric transducer. On the tyrosinase-SPCE strips, the oxidation reaction from catechol to o-quinone was catalyzed by tyrosinase. The tyrosinase-SPCE strips were modified with gold nanoparticles (AuNPs). In the presence of AuNPs of 25 nm diameter, the cathodic peak current of cyclic voltammetry (CV) was significantly enhanced by 5.2 fold. Under optimized conditions (250 μM catechol, 50 mM phosphate buffer, and pH 6.5), the linear response of the tyrosinase-SPCE strips ranged from 31.25 to 500 μM GSH, with a detection limit of approximately 35 μM (S/N > 3). The tyrosinase-SPCE strips have been used to detect real samples of plasma and tissue homogenates in a mouse experiment. The mice were orally administrated with N-acetylcysteine (NAC) 100 mg kg-1 once a day for 7 days; the plasma GSH significantly enhanced 2.8 fold as compared with saline-treated mice (1123 vs. 480 μM μg-1 protein). NAC administration also could alleviate the adverse effect of GSH reduction in the mice treated with doxorubicin.

Enzymes Immobilized into Starch- and Gelatin-Based Hydrogels: Properties and Application in Inhibition Assay

The present work is a review of the research on using hydrogels based on natural biodegradable polymers, starch, and gelatin for enzyme immobilization. This review addresses the main properties of starch and gelatin that make them promising materials in biotechnology for producing enzyme preparations stable during use and storage and insensitive to chemical and physical impacts. The authors summarize their achievements in developing the preparations of enzymes immobilized in starch and gelatin gels and assess their activity, stability, and sensitivity for use as biorecognition elements of enzyme inhibition-based biosensors.

Point-of-care detection of glycated hemoglobin using a novel dry chemistry-based electrochemiluminescence device

As a good biomarker to reflect the average level of blood glucose, glycated hemoglobin (HbA1c) is mainly used for long-term glycemic monitoring and risk assessment of complications in diabetic patients. Previous analysis methods for HbA1c usually require complex pretreatment processes and large-scale biochemical analyzers, which makes it difficult to realize the point-of-care testing (POCT) of HbA1c. In this work, we have proposed a three-electrode dry chemistry-based electrochemiluminescence (ECL) biosensor and its self-contained automatic ECL analyzer. In this enzymatic biosensor, fructosyl amino-caid oxidase (FAOD) reacts with the hydrolysis product of HbA1c, and the produced hydrogen peroxide further reacts with luminol under the appropriate driving voltage, generating photons to realize the quantitative detection of HbA1c. Under optimized conditions, the biosensors have a good linear response to different concentrations of fructosyl valine (FV) ranging from 0.05 to 2 mM, with a limit of detection of 2 μM. The within-batch variation is less than 15%, and the biosensors still have 78% of the initial response after the accelerated aging test of 36 h at 37 °C. Furthermore, the recoveries for different concentrations of samples in whole blood were within 92.3-99.7%. These results illustrate that the proposed method has the potential for use in POCT of HbA1c.

Field-effect transistors engineered via solution-based layer-by-layer nanoarchitectonics

The layer-by-layer (LbL) technique has been proven to be one of the most versatile approaches in order to fabricate functional nanofilms. The use of simple and inexpensive procedures as well as the possibility to incorporate a very wide range of materials through different interactions have driven its application in a wide range of fields. On the other hand, field-effect transistors (FETs) are certainly among the most important elements in electronics. The ability to modulate the flowing current between a source and a drain electrode via the voltage applied to the gate electrode endow these devices to switch or amplify electronic signals, being vital in all of our everyday electronic devices. In this topical review, we highlight different research efforts to engineer field-effect transistors using the LbL assembly approach. We firstly discuss on the engineering of the channel material of transistors via the LbL technique. Next, the deposition of dielectric materials through this approach is reviewed, allowing the development of high-performance electronic components. Finally, the application of the LbL approach to fabricate FETs-based biosensing devices is also discussed, as well as the improvement of the transistor's interfacial sensitivity by the engineering of the semiconductor with polyelectrolyte multilayers.

Receptor-based detection of microplastics and nanoplastics: Current and future

Plastic pollution is an emerging environmental concern, gaining significant attention worldwide. They are classified into microplastics (MP; defined from 1 μm to 5 mm) and smaller nanoplastics (NP; <1 μm). NPs may pose higher ecological risks than MPs. Various microscopic and spectroscopic techniques have been used to detect MPs, and the same methods have occasionally been used for NPs. However, they are not based on receptors, which provide high specificity in most biosensing applications. Receptor-based micro/nanoplastics (MNP) detection can provide high specificity, distinguishing MNPs from the environmental samples and, more importantly, identifying the plastic types. It can also offer a low limit of detection (LOD) required for environmental screening. Such receptors are expected to detect NPs specifically at the molecular level. This review categorizes the receptors into cells, proteins, peptides, fluorescent dyes, polymers, and micro/nanostructures. Detection techniques used with these receptors are also summarized and categorized. There is plenty of room for future research to test for broader classes of environmental samples and many plastic types, to lower the LOD, and to apply the current techniques for NPs. Portable and handheld MNP detection should also be demonstrated for field use since the current demonstrations primarily utilized laboratory instruments. Detection on microfluidic platforms will also be crucial in miniaturizing and automating the assay and, eventually, collecting an extensive database to support machine learning-based classification of MNP types.

A Novel Electrochemical Biosensor Based on Polyaniline-Embedded Copper Oxide Nanoparticles for High-Sensitive Paraoxon-Ethyl (PE) Detection

This paper proposes a fabrication of a hyper-sensitive amperometric biosensor for paraoxon-ethyl (PE) detection. In this developed biosensor, polyaniline (PANI) and copper oxide (CuO)-based nanocomposite is used as a sensing platform. The homogeneous distribution of CuO onto the PANI matrix enhances the surface area and conductivity of the nanocomposite. Additionally, the PANI produces a compatible environment for enzyme immobilization, which further enhances the rate of electron transfer. For biosensor fabrication, the nanocomposite is deposited electrophoretically onto the ITO glass substrate and immobilization of acetylcholinesterase (AChE) enzyme is conducted onto the fabricated electrode surface. The results validate good reproducibility, good stability, and high selectivity of the fabricated biosensor (AChE/PANI@CuO/ITO). The inhibition rate of paraoxon-ethyl (PE) is recorded in the concentration range of 1-200 nM with a low limit of detection of 0.096 nM or 96 pM. The sensitivity of the developed biosensor is found to be 49.86 µA(nM)^-1. The developed biosensor is further successfully accomplished for the detection of PE in real samples like rice and pulse.

Recent Advances in Nanomaterial-Based Sensing for Food Safety Analysis

The increasing public attention on unceasing food safety incidents prompts the requirements of analytical techniques with high sensitivity, reliability, and reproducibility to timely prevent food safety incidents occurring. Food analysis is critically important for the health of both animals and human beings. Due to their unique physical and chemical properties, nanomaterials provide more opportunities for food quality and safety control. To date, nanomaterials have been widely used in the construction of sensors and biosensors to achieve more accurate, fast, and selective food safety detection. Here, various nanomaterial-based sensors for food analysis are outlined, including optical and electrochemical sensors. The discussion mainly involves the basic sensing principles, current strategies, and novel designs. Additionally, given the trend towards portable devices, various smartphone sensor-based point-of-care (POC) devices for home care testing are discussed.

Biopolymer Composites with Sensors for Environmental and Medical Applications

One of the biggest economic and environmental sustainability problems is the over-reliance on petroleum chemicals in polymer production. This paper presents an overview of the current state of knowledge on biopolymers combined with biosensors in terms of properties, compounding methods and applications, with a focus on medical and environmental aspects. Therefore, this article is devoted to environmentally friendly polymer materials. The paper presents an overview of the current state of knowledge on biopolymers combined with biosensors in terms of properties, compounding methods and applications, with a special focus on medical and environmental aspects. The paper presents the current state of knowledge, as well as prospects. The article shows that biopolymers made from renewable raw materials are of great interest in various fields of science and industry. These materials not only replace existing polymers in many applications, but also provide new combinations of properties for new applications. Composite materials based on biopolymers are considered superior to traditional non-biodegradable materials due to their ability to degrade when exposed to environmental factors. The paper highlights the combination of polymers with nanomaterials which allows the preparation of chemical sensors, thus enabling their use in environmental or medical applications due to their biocompatibility and sensitivity. This review focuses on analyzing the state of research in the field of biopolymer-sensor composites.

Biosensors toward behavior detection in diagnosis of alzheimer’s disease

In recent years, a huge number of individuals all over the world, elderly people, in particular, have been suffering from Alzheimer’s disease (AD), which has had a significant negative impact on their quality of life. To intervene early in the progression of the disease, accurate, convenient, and low-cost detection technologies are gaining increased attention. As a result of their multiple merits in the detection and assessment of AD, biosensors are being frequently utilized in this field. Behavioral detection is a prospective way to diagnose AD at an early stage, which is a more objective and quantitative approach than conventional neuropsychological scales. Furthermore, it provides a safer and more comfortable environment than those invasive methods (such as blood and cerebrospinal fluid tests) and is more economical than neuroimaging tests. Behavior detection is gaining increasing attention in AD diagnosis. In this review, cutting-edge biosensor-based devices for AD diagnosis together with their measurement parameters and diagnostic effectiveness have been discussed in four application subtopics: body movement behavior detection, eye movement behavior detection, speech behavior detection, and multi-behavior detection. Finally, the characteristics of behavior detection sensors in various application scenarios are summarized and the prospects of their application in AD diagnostics are presented as well.

Emerging bioanalytical sensors for rapid and close-to-real-time detection of priority abiotic and biotic stressors in aquaculture and culture-based fisheries

Abiotic stresses of various chemical contamination of physical, inorganic, organic and biotoxin origin and biotic stresses of bacterial, viral, parasitic and fungal origins are the significant constraints in achieving higher aquaculture production. Testing and rapid detection of these chemical and microbial contaminants are crucial in identifying and mitigating abiotic and biotic stresses, which has become one of the most challenging aspects in aquaculture and culture-based fisheries. The classical analytical techniques, including titrimetric methods, spectrophotometric, mass spectrometric, spectroscopic, and chromatographic techniques, are tedious and sometimes inaccessible when required. The development of novel and improved bioanalytical methods for rapid, selective and sensitive detection is a wide and dynamic field of research. Biosensors offer precise detection of biotic and abiotic stressors in aquaculture and culture-based fisheries within no time. This review article allows filling the knowledge gap for detection and monitoring of chemical and microbial contaminants of abiotic and biotic origin in aquaculture and culture-based fisheries using nano(bio-) analytical technologies, including nano(bio-)molecular and nano(bio-)sensing techniques.

Fundamentals of Biosensors and Detection Methods

Biosensors have a great impact on our society to enhance the life quality, playing an important role in the development of Point-of-Care (POC) technologies for rapid diagnostics, and monitoring of disease progression. COVID-19 rapid antigen tests, home pregnancy tests, and glucose monitoring sensors represent three examples of successful biosensor POC devices. Biosensors have extensively been used in applications related to the control of diseases, food quality and safety, and environment quality. They can provide great specificity and portability at significantly reduced costs. In this chapter are described the fundamentals of biosensors including the working principles, general configurations, performance factors, and their classifications according to the type of bioreceptors and transducers. It is also briefly illustrated the general strategies applied to immobilize biorecognition elements on the transducer surface for the construction of biosensors. Moreover, the principal detection methods used in biosensors are described, giving special emphasis on optical, electrochemical, and mass-based methods. Finally, the challenges for biosensing in real applications are addressed at the end of this chapter.

Wearable biosensors for human fatigue diagnosis: A review

Fatigue causes deleterious effects to physical and mental health of human being and may cause loss of lives. Therefore, the adverse effects of fatigue on individuals and the society are massive. With the ever-increasing frequency of overtraining among modern military and sports personnel, timely, portable and accurate fatigue diagnosis is essential to avoid fatigue-induced accidents. However, traditional detection methods require complex sample preparation and blood sampling processes, which cannot meet the timeliness and portability of fatigue diagnosis. With the development of flexible materials and biosensing technology, wearable biosensors have attracted increased attention to the researchers. Wearable biosensors collect biomarkers from noninvasive biofluids, such as sweat, saliva, and tears, followed by biosensing with the help of biosensing modules continuously and quantitatively. The detection signal can then be transmitted through wireless communication modules that constitute a method for real-time understanding of abnormality. Recent developments of wearable biosensors are focused on miniaturized wearable electrochemistry and optical biosensors for metabolites detection, of which, few have exhibited satisfactory results in medical diagnosis. However, detection performance limits the wide-range applicability of wearable fatigue diagnosis. In this article, the application of wearable biosensors in fatigue diagnosis has been discussed. In fact, exploration of the composition of different biofluids and their potential toward fatigue diagnosis have been discussed here for the very first time. Moreover, discussions regarding the current bottlenecks in wearable fatigue biosensors and the latest advancements in biochemical reaction and data communication modules have been incorporated herein. Finally, the main challenges and opportunities were discussed for wearable fatigue diagnosis in the future.

Recent Trends in Biosensors for Environmental Quality Monitoring

The monitoring of environmental pollution requires fast, reliable, cost-effective and small devices. This need explains the recent trends in the development of biosensing devices for pollutant detection. The present review aims to summarize the newest trends regarding the use of biosensors to detect environmental contaminants. Enzyme, whole cell, antibody, aptamer, and DNA-based biosensors and biomimetic sensors are discussed. We summarize their applicability to the detection of various pollutants and mention their constructive characteristics. Several detection principles are used in biosensor design: amperometry, conductometry, luminescence, etc. They differ in terms of rapidity, sensitivity, profitability, and design. Each one is characterized by specific selectivity and detection limits depending on the sensitive element. Mimetic biosensors are slowly gaining attention from researchers and users due to their advantages compared with classical ones. Further studies are necessary for the development of robust biosensing devices that can successfully be used for the detection of pollutants from complex matrices without prior sample preparation.

Magnetism-Controllable Catalytic Activity of DNAzyme

Controllable regulation of enzyme activity is an important prerequisite for the in-depth application of enzymes, especially in today's intelligent era. However, irreversible regulation and cumbersome operation make this goal difficult to achieve. Here, by adopting magnetism and a harmless, noncontact, and time- and space-controllable physical element, we developed a system that could conveniently and reversibly regulate the activity of DNAzyme. In this system, the strands of the DNAzyme could be stretched or folded by applying or removing a magnetic field. Thereby, the conformation-dependent endonuclease activity of the DNAzyme could be facilely switched between an "OFF" and "ON" state. This system provides a reusable platform for the control of enzyme catalytic activity through magnetism, which provides guidance for further application in some related scientific research, especially the regulation of the activity of conformation-dependent polymers (DNAzymes, aptamers, and peptides).

Research progress of smart response composite hydrogels based on nanocellulose

In recent years, smart-responsive nanocellulose composite hydrogels have attracted extensive attention due to their unique porous substrate, hydrophilic properties, biocompatibility and stimulus responsiveness. At present, the research on smart response nanocellulose composite hydrogel mainly focuses on the selection of composite materials and the construction of internal chemical bonds. The common composite materials and connection methods used for preparation of smart response nanocellulose composite hydrogels are compared according to the different types of response sources such as temperature, pH and so on. The response mechanisms and the application prospects of different response types of nanocellulose composite hydrogels are summarized, and the transformation of internal ions, functional groups and chemical bonds, as well as the changes in mechanical properties such as modulus and strength are discussed. Finally, the shortcomings and application prospects of nanocellulose smart response composite hydrogels are summarized and prospected.

A Novel 3D Hierarchical Plasmonic Functional Cu@Co3O4@Ag Array as Intelligent SERS Sensing Platform with Trace Droplet Rapid Detection Ability for Pesticide Residue Detection on Fruits and Vegetables

Rapid and effective detection of pesticide residues from complex surfaces of fruits and vegetables has important significance. Herein, we report a novel three-dimensional (3D) hierarchical porous functional surface-enhanced Raman scattering (SERS) substrate, which is fabricated by successive two-step hydrothermal synthesis strategy of silver nanoparticles (Ag NPs) and cobalt oxide nanowires (Co₃O₄ NWs) on the 3D copper foam framework as Cu@Co₃O₄@Ag-H. The strategy offers a new avenue for localized plasmonic materials distribution and construction, which exhibits better morphology regulation ability and SERS activity (or hotspots engineering) than physical spurring obtained Cu@Co₃O₄@Ag-S. The developed Cu@Co₃O₄@Ag-H possesses large surface area and rich hotspots, which contributes to the excellent SERS performance, including homogeneity (RSD of 7.8%), sensitivity (enhancement factor, EF of 2.24 × 10⁸) and stability. The Cu@Co₃O₄@Ag-H not only provides plenty of Electromagnetic enhancement (EM) hotspots but also the trace detection capability for droplet rapid sensing within 2 s. Cu@Co₃O₄@Ag-H substrate is further developed as an effective SERS sensing platform for pesticide residues detection on the surfaces of fruits and vegetables with excellent LOD of 0.1 ppm, which is lower than the most similar reported works. This work offers new potential for bioassay, disease POCT diagnosis, national security, wearable flexible devices, energy storage and other related fields.

Biological protein mediated ferroptotic tumor nanotherapeutics

Ferroptosis, a cell death pathway involving iron-related generation of lipid hydroperoxides for achieving incredible tumor suppression, has reignited the hope of chemotherapy in tumor treatment in the past decade. With extensive research studies, various bioactive proteins and cellular pathways have been demonstrated to regulate the occurrence and development of ferroptosis. The gradually established ferroptotic regulatory network is conducive to find effective proteins from a holistic perspective and guides better designs for future ferroptotic tumor therapies. The first section of this review summarizes the recent advances in ferroptotic regulatory mechanisms of proteins and attempts to clarify their latent function in the ferroptotic regulatory network. Second, the existing protein-mediated ferroptotic tumor nanotherapeutic strategies were reviewed, including the protein-mediated iron supplement, cell membrane transporter inhibition, glutathione peroxidase 4 interference, glutathione depletion, bioenzyme-mediated reactive oxygen species generation, heat shock protein inhibition, and tumor-overexpressed protein-triggered drug release for ferroptotic therapy. Finally, the future expectations and challenges of ferroptotic tumor nanotherapeutics for clinical cancer therapy are highlighted.

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.

Engineered tyrosinases with broadened bio-catalysis scope: immobilization using nanocarriers and applications

Enzyme immobilization is a widely used technology for creating more stable, active, and reusable biocatalysts. The immobilization process also improves the enzyme's operating efficiency in industrial applications. Various support matrices have been designed and developed to enhance the biocatalytic efficiency of immobilized enzymes. Given their unique physicochemical attributes, including substantial surface area, rigidity, semi-conductivity, high enzyme loading, hyper catalytic activity, and size-assisted optical properties, nanomaterials have emerged as fascinating matrices for enzyme immobilization. Tyrosinase is a copper-containing monooxygenase that catalyzes the o-hydroxylation of monophenols to catechols and o-quinones. This enzyme possesses a wide range of uses in the medical, biotechnological, and food sectors. This article summarizes an array of nanostructured materials as carrier matrices for tyrosinase immobilization. Following a detailed background overview, various nanomaterials, as immobilization support matrices, including carbon nanotubes (CNTs), carbon dots (CDs), carbon black (CB), nanofibers, Graphene nanocomposite, platinum nanoparticles, nano-sized magnetic particles, lignin nanoparticles, layered double hydroxide (LDH) nanomaterials, gold nanoparticles (AuNPs), and zinc oxide nanoparticles have been discussed. Next, applied perspectives have been spotlights with particular reference to environmental pollutant sensing, phenolic compounds detection, pharmaceutical, and food industry (e.g., cereal processing, dairy processing, and meat processing), along with other miscellaneous applications.

Office Paper-Based Electrochemical Strips for Organophosphorus Pesticide Monitoring in Agricultural Soil

Although the use of pesticides has highlighted obvious advantages on agricultural yields, intensive and widespread pesticide use raises serious environmental and health concerns. In particular, organophosphate pesticides represent >40% of the totality used in the field of agriculture, and developing countries face the issue of agricultural poisoning, also due to scarce monitoring programs. In this work, a decentralized, miniaturized, sustainable, and portable paper-based electrochemical biosensor for the quantification of organophosphorus pesticides' level has been realized. The proposed approach highlights the use of a very common paper-based substrate, namely, office paper. Office paper offers several advantages due to its nature: it allows one to print conductive strips for electrochemical connection, loading bio-hybrid nanosized probes (Prussian blue, carbon black, and butyrylcholinesterase), evaluating pesticides and reducing waste disposal compared to plastic-based strips. The portable system has been characterized by a low detection limit of 1.3 ng/mL, and accordingly to total discovered pesticide contents in EU agricultural soils, up to ca. 3 μg/mL, it can offer a valuable tool for fast monitoring. To demonstrate its effectiveness, soil and fruit vegetables have been used to perform in situ quantification. Good recovery percentages between 90 and 110% have been achieved in different matrices, highlighting to be suitable for field measurements, and a good correlation has been obtained in comparison with LC-MS analysis.

Minimizing transient microenvironment-associated variability for analysis of environmental anthropogenic contaminants via ambient ionization

The rapid and quantitative analysis of anthropogenic contaminants in environmental matrices is crucial for regulatory testing and to elucidate the environmental fate of these pollutants. Direct ambient mass spectrometry (AMS) methodologies greatly increase sample throughput, can be adapted for onsite analysis and are often regarded as semi-quantitative by most developed protocols. One of the limitations of AMS, especially for on site analysis applications, is the irreproducibility of the measurements related to the occurrence of transient microenvironments (TME) and variable background interferences. In this work we report an effective strategy to minimize these effects by hyphenating, for the first time, solid phase microextraction (SPME) arrow to mass spectrometry via a thermal desorption unit (TDU) and direct analysis in real time (DART) source. The developed method was optimized for the extraction and analysis of pesticides and pharmaceuticals from surface water. It was demonstrated that the hyphenation of the SPME and TDU-DART resulted in reduced background contamination, indicating the suitability of the method for onsite analysis even in variable and non-ideal environments. Model analytes were quantitated in the low μg/L range with a total analysis time of less than 5 min, linear dynamic ranges (LDR) and interday reproducibility for most compounds being 2.5-500 μg/L and lower than 10%, respectively. The developed approach provides an excellent analytical tool that can be applied for the onsite high-throughput analysis of water samples as well as air and aereosols. Considering the tunability of our extraction process, time-resolved environmental monitoring can be achieved onsite within minutes.

Silk Fibroin As an Immobilization Matrix for Sensing Applications

The development of flexible, biocompatible, and environment-friendly sensors has attracted a significant amount of scientific interest for the past few decades. Among all the natural materials, silk fibroin (SF), due to its tunable biodegradability, biocompatibility, ease of processing, presence of functional groups, and controllable dimensions, has opened up opportunities for immobilizing multitudinous biomolecules and conformability to the skin, among other attractive opportunities. The silk fibroins also offer good physical properties, such as superior toughness and tensile strength. The sensors made of SF as an immobilization matrix have demonstrated excellent analytical performance, sensing even at low concentrations. The significant advantage of silk fibroins is the presence of functional groups along with a controllable conformation transition that enables immobilization of receptor molecules using silk fibroins as an immobilization matrix enables us to entrap the receptor molecules without using any chemical reagents. This review encompasses a detailed discussion on sensors, the advantages of using silk fibroins as an immobilization matrix for various receptors, their applications, and the future research scope in this state-of-the-art technology based upon the explorable applications for silk fibroin-based sensors.

Expression of Drosophila melanogaster acetylcholinesterase (DmAChE) gene splice variants in Pichia pastoris and evaluation of its sensitivity to organophosphorus pesticides

Acetylcholinesterase (AChE) is a key enzyme used to detect organophosphorus pesticide residues by the enzyme inhibition method. An accidental discovery of a mutant strain with AChE activity was made in our laboratory during the process of AChE expression by Pichia pastoris. The pPIC9K-Drosophilamelanogaster acetylcholinesterase (DmAChE)-like expression vector was constructed by codon optimization of this mutant strain, which was transformed into P. pastoris GS115, and positive clones were selected on yeast peptone dextrose (YPD) plate with G418 at 4.0 mg/mL. The GS115-pPIC9K-DmAChE-like strain was subjected to 0.5% methanol induction expression for 120 h, with a protein band at 4.3 kDa found by the tricine-sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) pattern of the fermentation supernatant. After preliminary purification by ammonium sulfate precipitation, the enzyme activity was detected to be 76.9 U/(mL⋅min). In addition, the pesticide sensitivity test proved that DmAChE-like is selective and sensitive to organophosphorus pesticides.

Designing of Nanomaterials-Based Enzymatic Biosensors: Synthesis, Properties, and Applications

Among the many biological entities employed in the development of biosensors, enzymes have attracted the most attention. Nanotechnology has been fostering excellent prospects in the development of enzymatic biosensors, since enzyme immobilization onto conductive nanostructures can improve characteristics that are crucial in biosensor transduction, such as surface-to-volume ratio, signal response, selectivity, sensitivity, conductivity, and biocatalytic activity, among others. These and other advantages of nanomaterial-based enzymatic biosensors are discussed in this work via the compilation of several reports on their applications in different industrial segments. To provide detailed insights into the state of the art of this technology, all the relevant concepts around the topic are discussed, including the properties of enzymes, the mechanisms involved in their immobilization, and the application of different enzyme-derived biosensors and nanomaterials. Finally, there is a discussion around the pressing challenges in this technology, which will be useful for guiding the development of future research in the area.

Mathematical Modelling of Biosensing Platforms Applied for Environmental Monitoring

In recent years, mathematical modelling has known an overwhelming integration in different scientific fields. In general, modelling is used to obtain new insights and achieve more quantitative and qualitative information about systems by programming language, manipulating matrices, creating algorithms and tracing functions and data. Researchers have been inspired by these techniques to explore several methods to solve many problems with high precision. In this direction, simulation and modelling have been employed for the development of sensitive and selective detection tools in different fields including environmental control. Emerging pollutants such as pesticides, heavy metals and pharmaceuticals are contaminating water resources, thus threatening wildlife. As a consequence, various biosensors using modelling have been reported in the literature for efficient environmental monitoring. In this review paper, the recent biosensors inspired by modelling and applied for environmental monitoring will be overviewed. Moreover, the level of success and the analytical performances of each modelling-biosensor will be discussed. Finally, current challenges in this field will be highlighted.

Label-free optical antibody testing kit based on a self-assembled whispering-gallery-mode microsphere

The appearance of antibodies in blood is a critical signal to suggest the infection. A rapid and accurate detection method for the antibody is significant to the disease diagnosis, especially for the epidemic. To this end, a highly sensitive whispering-gallery-mode (WGM) optical testing kit is designed and fabricated for detecting the specific immunoglobulin antibodies. The key component of the kit is a silica self-assembled microsphere decorated with the nucleocapsid proteins (N-proteins) of the SARS-CoV-2 virus. After the N-protein antibody immunoglobulin G (N-IgG) and immunoglobulin M (N-IgM) solutions being injected into the kit, the WGM red-shifts due to the antigen-antibody reaction. The wavelength displacement rates are proportional to the concentrations of these two antibodies from 1 to 100 μg/mL. A good specificity of the kit is demonstrated by the nonspecific human immunoglobulin G (H-IgG) and immunoglobulin M (H-IgM).

Software for Matching Standard Activity Enzyme Biosensors for Soil Pollution Analysis

This work is dedicated to developing enzyme biosensor software to solve problems regarding soil pollution analysis. An algorithm and specialised software have been developed which stores, analyses and visualises data using JavaScript programming language. The developed software is based on matching data of 51 non-commercial standard soil samples and their inhibitory effects on three enzyme systems of varying complexity. This approach is able to identify the influence of chemical properties soil samples, without toxic agents, on enzyme biosensors. Such software may find wide use in environmental monitoring.

Pesticide exposure and adverse health effects associated with farmwork in Northern Thailand

OBJECTIVES

To assess pesticide exposure and understand the resultant health effects of agricultural workers in Northern Thailand.

METHODS

This was a cross-sectional study. We quantified exposure to pesticides, including chlorpyrifos, methomyl, and metalaxyl, by air sampling and liquid chromatography/mass spectrometry. We estimated differences in self-reported health outcomes, complete blood counts, cholinesterase activity, and serum/urine calcium and creatinine concentrations at baseline between farmworkers and comparison workers, and after pesticide spraying in farmworkers only.

RESULTS

This study included 97 men between the ages of 22 and 76 years; 70 were conventional farmworkers; and 27 did not report any prior farmwork or pesticide spraying. None of the farmworkers wore standardized personal protective equipment (PPE) for the concentrated chemicals they were working with. Methomyl (8.4-13 481.9 ng/m3 ), ethyl chlorpyrifos (11.6-67 759 ng/m3 ), and metalaxyl (13.9-41 191.3 ng/m3 ) were detected via personal air sampling. When it came to reporting confidence in the ability to handle personal problems, only 43% of farmworkers reported feeling confident, which reflects higher stress levels in comparison to 78% of comparison workers (P = .028). Farmworkers also had significantly lower monocyte counts (P = .01), serum calcium (P = .01), red blood count (P = .01), white blood cell count (P = .04), and butyrylcholinesterase activity (P < .0001), relative to comparison workers. After adjusting for body mass index (BMI), age, and smoking, methomyl air concentrations were associated with a decrease in farmworker acetylcholinesterase activity (beta = -0.327, P = .016).

CONCLUSIONS

This population of farmworkers had significant alterations in stress measures and clinical biomarkers, including decreased blood cell counts and cholinesterase activity, relative to matched controls. These changes are potentially linked to occupational pesticide exposures. Improving PPE use presents a likely route for preventive intervention in this population.

Enhancement of Probe Density in DNA Sensing by Tuning the Exponential Growth Regime of Polyelectrolyte Multilayers

Surface-based biosensing devices benefit from a dedicated design of the probe layer present at the transducing interface. The layer architecture, its physicochemical properties, and the embedding of the receptor sites affect the probability of binding the analyte. Here, the enhancement of the probe density at the sensing interface by tuning the exponential growth regime of polyelectrolyte multilayers (PEMs) is presented. PEMs were made of poly-l-lysine (PLL), with appended clickable dibenzocyclooctyne (DBCO) groups and oligo(ethylene glycol) chains, and poly(styrene sulfonate) (PSS). The DNA probe loading and target hybridization efficiencies of the PEMs were evaluated as a function of the PLL layer number and the growth regime by a quartz crystal microbalance (QCM). An amplification factor of 25 in the target DNA detection was found for a 33-layer exponentially grown PEM compared to a monolayer. A Voigt-based model showed that DNA probe binding to the DBCO groups is more efficient in the open, exponentially grown films, while the hybridization efficiencies appeared to be high for all layer architectures. These results show the potential of such engineered gel-like structures to increase the detection of bio-relevant analytes in biosensing systems.

Conducting polymer-based electrochemical biosensor for the detection of acetylthiocholine and pesticide via acetylcholinesterase

A voltammetric biosensor for acetylthiocholine (ATCh) and paraoxon detection was successfully developed. To achieve this goal, polypyrrole (PPy) was synthesized onto the platinum (Pt) electrode surface in 0.30 M oxalic acid solution containing 25 mM pyrrole. PPy-coated Pt (Pt/PPy) electrode surface was covered with chitosan (Chi) (Pt/PPy/Chi). The acetylcholinesterase (AChE) enzyme was immobilized on the Pt/PPy/Chi electrode surface to build a voltammetric biosensor (Pt/PPy/Chi/AChE). The storage stability of the biosensor was determined to be 72% even after 60 days. The operational stability was determined to be 94% after 20 consecutive measurements. For the biosensor, the linear range was determined to be 30-50 µM for ATCh and 0.46-1.84 nM for paraoxon. The limit of detection (LOD) was determined to be 0.45 µM for ATCh and 0.17 nM for paraoxon.

Electrochemical sensors and biosensors using laser-derived graphene: A comprehensive review

Laser-derived graphene (LDG) technology is gaining attention as a promising material for the development of novel electrochemical sensors and biosensors. Compared to established methods for graphene synthesis, LDG provides many advantages such as cost-effectiveness, fast electron mobility, mask-free, green synthesis, good electrical conductivity, porosity, mechanical stability, and large surface area. This review discusses, in a critical way, recent advancements in this field. First, we focused on the fabrication and doping of LDG platforms using different strategies. Next, the techniques for the modification of LDG sensors using nanomaterials, conducting polymers, biological and artificial receptors are presented. We then discussed the advances achieved for various LDG sensing and biosensing schemes and their applications in the fields of environmental monitoring, food safety, and clinical diagnosis. Finally, the drawbacks and limitations of LDG based electrochemical biosensors are addressed, and future trends are also highlighted.

Enzymatic assays for the assessment of toxic effects of halogenated organic contaminants in water and food. A review

Halogenated organic compounds are a particular group of contaminants consisting of a large number of substances, and of great concern due to their persistence in the environment, potential for bioaccumulation and toxicity. Some of these compounds have been classified as persistent organic pollutants (POPs) under The Stockholm Convention and many toxicity assessments have been conducted on them previously. In this work we provide an overview of enzymatic assays used in these studies to establish toxic effects and dose-response relationships. Studies in vivo and in vitro have been considered with a particular emphasis on the impact of halogenated compounds on the activity of relevant enzymes to the humans and the environment. Most information available in the literature focuses on chlorinated compounds, but brominated and fluorinated molecules are also the target of increasing numbers of studies. The enzymes identified can be classified as enzymes: i) the activities of which are affected by the presence of halogenated organic compounds, and ii) those involved in their metabolisation/detoxification resulting in increased activities. In both cases the halogen substituent seems to have an important role in the effects observed. Finally, the use of these enzymes in biosensing tools for monitoring of halogenated compounds is described.