Recent advances on portable sensing and biosensing assays applied for detection of main chemical and biological pollutant agents in water samples: A critical review

Synthesis and application of bismuth nanoparticle-loaded longan porous carbon for simultaneous electrochemical determination of Pb(II) and cd(II) in seafoods

The discarded longan shell-derived porous carbon material (LPC) served as a scaffold for synthesizing bismuth nanoparticle-loaded longan porous carbon nanocomposite (BiNPs@LPC) via a hydrothermal method. Then BiNPs@LPC was utilized to modify screen-printed carbon electrodes (SPCE) for simultaneous detection of Pb(II) and Cd(II) by square wave anodic stripping voltammetry (SWASV). The material was thoroughly characterized by scanning electron microscopy, X-ray diffraction, Raman spectra, Brunauer-Emmett-Teller analysis, electrochemical impedance spectroscopy and cyclic voltammetry. BiNPs@LPC exhibited abundant porous structures, high surface area, and numerous active sites, which could improve significantly response sensitivity. Under optimal conditions, the peak currents of Pb(II) and Cd(II) exhibited favorable linear relationships with the concentration within a range of 0.1-150 μg L-1, with detection limits (S/N = 3) of 0.02 μg L-1 and 0.03 μg L-1, respectively. BiNPs@LPC/SPCE demonstrated remarkable selectivity, stability and repeatability. The proposed method was successfully applied for the detection of Pb(II) and Cd(II) in seafoods achieving satisfying recovery of 97.8%-108.3% and 96.7%-106.4%. These excellent test properties were coupled with convenience for batch preparation of the modified electrodes, highlighting its potential for practical applications in heavy metal detection of real samples.

Aptamer biosensor design for the detection of endocrine-disrupting chemicals small organic molecules using novel bioinformatics methods

Endocrine-disrupting chemicals (EDCs) are substances that can disrupt the normal functioning of hormones.Using aptamers, which are biological recognition elements, biosensors can quickly and accurately detect EDCs in environmental samples. However, the elucidation of aptamer structures by conventional methods is highly challenging due to their complexity. This has led to the development of three-dimensional aptamer structures based on different models and techniques. To do this, we developed a way to predict the 3D structures of the SS DNA needed for this sequence by starting with an aptamer sequence that has biosensor properties specific to bisphenol-A (BPA), one of the chemicals found in water samples that can interfere with hormones. In addition, we will elucidate the intermolecular mechanisms and binding affinity between aptamers and endocrine disruptors using bioinformatics techniques such as molecular docking, molecular dynamics simulation, and binding energies. The outcomes of our study are to compare modeling programs and force fields to see how reliable they are and how well they agree with results found in the existing literature, to understand the intermolecular mechanisms and affinity of aptamer-based biosensors, and to find a new way to make aptamers that takes less time and costs less.

Aza-BODIPY-based logic gate chemosensors and their applications

Dimethylaniline-substituted aza-BODIPY dyes (DA, DM, DP) were designed and synthesized aiming for ion detection. The Zn2+ recognition ability was found in all compounds and the binding mechanism was possibly via dimethylaniline sites linked to the aza-BODIPY core. Upon Zn2+ addition, the new absorption band and the color change occurred due to the altered charge transfer of the adducts. The custom-made colorimeter was successfully integrated into the dye's application, demonstrating a good linear relationship between resistance values and Zn2+ concentration. The chromophore test strips were fabricated and exhibited distinct color changes upon aqueous Zn2+ exposure. The compound DA also exhibits logical behavior with DA-Zn2+-Cu2+ system. In terms of environmental hazards, the compounds exhibited no adverse effect on Pseudomonas putida at the concentration level of 0.2 mg/mL. These findings indicated that all synthesized aza-BODIPYs might be suitable for chemosensor probes for Zn2+ detection with possibly low environmental risk.

Biogenic fabrication of a gold nanoparticle sensor for detection of Fe3+ ions using a smartphone and machine learning

In recent years, smartphones have been integrated into rapid colorimetric sensors for heavy metal ions, but challenges persist in accuracy and efficiency. Our study introduces a novel approach to utilize biogenic gold nanoparticle (AuNP) sensors in conjunction with designing a lightbox with a color reference and machine learning for detection of Fe3+ ions in water. AuNPs were synthesized using the aqueous extract of Eleutherine bulbosa leaf as reductants and stabilizing agents. Physicochemical analyses revealed diverse AuNP shapes and sizes with an average size of 19.8 nm, with a crystalline structure confirmed via SAED and XRD techniques. AuNPs exhibited high sensitivity and selectivity in detection of Fe3+ ions through UV-vis spectroscopy and smartphones, relying on nanoparticle aggregation. To enhance image quality, we developed a lightbox and implemented a reference color value for standardization, significantly improving performance of machine learning algorithms. Our method achieved approximately 6.7% higher evaluation metrics (R 2 = 0.8780) compared to non-normalized approaches (R 2 = 0.8207). This work presented a promising tool for quantitative Fe3+ ion analysis in water.

Low temperature acclimation of electroactive microorganisms may be an effective strategy to enhance the toxicity sensing performance of microbial fuel cell sensors

Microbial fuel cell (MFC) sensing is a promising method for real-time detection of water biotoxicity, however, the low sensing sensitivity limits its application. This study adopted low temperature acclimation as a strategy to enhance the toxicity sensing performance of MFC biosensor. Two types of MFC biosensors were started up at low (10 °C) or warm (25 °C) temperature, denoted as MFC-Ls and MFC-Ws respectively, using Pb2+ as the toxic substance. MFC-Ls exhibited superior sensing sensitivities towards Pb2+ compared with MFC-Ws at both low (10 °C) and warm (25 °C) operation temperatures. For example, the inhibition rate of voltage of MFC-Ls was 22.81 % with 1 mg/L Pb2+ shock at 10 °C, while that of MFC-Ws was only 5.9 %. The morphological observation showed the anode biofilm of MFC-Ls had appropriate amount of extracellular polymer substances, thinner thickness (28.95 μm for MFC-Ls and 41.58 μm for MFC-Ws) and higher proportion of living cells (90.65 % for MFC-Ls and 86.01 % for MFC-Ws) compared to that of MFC-Ws. Microbial analysis indicated the enrichment of psychrophilic electroactive microorganisms and cold-active enzymes as well as their sensitivity to Pb2+ shock was the foundation for the effective operation and good performance of MFC-Ls biosensors. In conclusion, low temperature acclimation of electroactive microorganisms enhanced not only the sensitivity but also the temperature adaptability of MFC biosensors.

Integrating Wireless Remote Sensing and Sensors for Monitoring Pesticide Pollution in Surface and Groundwater

Water constitutes an indispensable resource crucial for the sustenance of humanity, as it plays an integral role in various sectors such as agriculture, industrial processes, and domestic consumption. Even though water covers 71% of the global land surface, governments have been grappling with the challenge of ensuring the provision of safe water for domestic use. A contributing factor to this situation is the persistent contamination of available water sources rendering them unfit for human consumption. A common contaminant, pesticides are not frequently tested for despite their serious effects on biodiversity. Pesticide determination in water quality assessment is a challenging task because the procedures involved in the extraction and detection are complex. This reduces their popularity in many monitoring campaigns despite their harmful effects. If the existing methods of pesticide analysis are adapted by leveraging new technologies, then information concerning their presence in water ecosystems can be exposed. Furthermore, beyond the advantages conferred by the integration of wireless sensor networks (WSNs), the Internet of Things (IoT), Machine Learning (ML), and big data analytics, a notable outcome is the attainment of a heightened degree of granularity in the information of water ecosystems. This paper discusses methods of pesticide detection in water, emphasizing the possible use of electrochemical sensors, biosensors, and paper-based sensors in wireless sensing. It also explores the application of WSNs in water, the IoT, computing models, ML, and big data analytics, and their potential for integration as technologies useful for pesticide monitoring in water.

Recent Advancements in Molecularly Imprinted Polymers Based Aptasensors: Critical Role of Nanomaterials for the Efficient Food Safety Analysis

Biosensors are being studied extensively for their ability to detect and analyze molecules. There has been a growing interest in combining molecular imprinted polymers (MIPs) and aptamers to create hybrid recognition elements that offer advantages such as target binding, sensitivity, selectivity, and stability. These hybrid elements have been successfully used in identifying a wide range of analytes in food samples. However, the application of MIP-based aptasensors in different sensing approaches is still challenging due to the low conductivity of MIPs-aptamers and limited adsorption capacity of MIPs. To address these limitations, researchers have been exploring the use of nanomaterials (NMs) to design efficient multiple-recognition systems that exploit the synergies between aptamers and MIPs. These hybrid systems can enhance the sensitivity and selectivity of MIP-based aptasensors in quantifying analytical samples. This review provides a comprehensive overview of recent advancements in the field of MIP-based aptasensors. It also introduces technologies that combine MIPs and aptamers to achieve higher sensitivity and selectivity in quantifying analytical samples. The review also highlights potential future trends and practical approaches that can be employed to address the limitations of MIP-based aptasensors, including the use of new NMs, the development of new fabrication techniques, and the integration of MIP-based aptasensors with other analytical tools.

A low-cost and portable fluorometer based on an optical pick-up unit for chlorophyll-a detection

Chlorophyll-a (Chl-a) fluorescence detection is an important technique for monitoring water quality. In this work, we proposed an approach that employs the mass-produced low-cost optical pick-up unit (OPU) extracted from the high-definition digital versatile disc (HD-DVD) drive as the key optical component for our chlorophyll-a fluorometer. The built-in blue-violet 405 nm laser diode of the OPU acts as the excitation light to perform laser-induced fluorescence (LIF). The laser driver and a series of intrinsic lenses within the OPU, such as an objective lens with a numerical aperture (NA) of 0.65 and a collimating lens, help reduce the size, cost, and system complexity of the fluorometer. By integrating off-the-shelf electronic components, miniaturized optical setups, and 3D-printed assemblies, we have developed a low-cost, easy-to-make, standalone, and portable fluorometer. Finally, we validated the performance of the device for chlorophyll-a fluorescence detection under laboratory and on-site conditions, which demonstrated its great potential in water monitoring applications. The limit of detection (LOD) for chlorophyll-a is 0.35 μg/L, the size of the device is 151 × 100 × 80 mm3, and the total cost of the proposed fluorometer is as low as 137.5 USD. © 2023 Elsevier Science. All rights reserved.

Morphology Control of Self-Assembled Copper Coordination Polymers for Glucose Assays

Low-cost analytical assays enable accessible detection of clinically and environmentally important analytes; however, common enzyme-based assays suffer from high production and storage costs. Catalytically active synthetic materials serve as replacements for natural enzymes, but development of cost-effective, highly efficient synthetic strategies remains a challenge. Here, we utilized a facile synthesis for copper bipyridine coordination polymers (CuBpyCPs) and investigated structure-function relationships to achieve optimal catalytic properties for a glucose assay. We demonstrated the manipulation of CuBpyCP morphology, resulting in nanoscale petal-like structures and microscale high-index faceted structures, and identified three pure crystal morphologies exhibiting a comparable catalytic activity (Km = 0.3-0.5 mM) to horseradish peroxidase.

A review on chitosan/metal oxide nanocomposites for applications in environmental remediation

A cleaner and safer environment is one of the most important requirements in the future. It has become increasingly urgent and important to fabricate novel environmentally-friendly materials to remove various hazardous pollutants. Compared with traditional materials, chitosan is a more environmentally friendly material due to its abundance, biocompatibility, biodegradability, film-forming ability and hydrophilicity. As an abundant of -NH2 and -OH groups on chitosan molecular chain could chelate with all kinds of metal ions efficiently, chitosan-based materials hold great potential as a versatile supporting matrix for metal oxide nanomaterials (MONMs) (TiO2, ZnO, SnO2, Fe3O4, etc.). Recently, many chitosan/metal oxide nanomaterials (CS/MONMs) have been reported as adsorbents, photocatalysts, heterogeneous Fenton-like agents, and sensors for potential and practical applications in environmental remediation and monitoring. This review analyzed and summarized the recent advances in CS/MONMs composites, which will provide plentiful and meaningful information on the preparation and application of CS/MONMs composites for wastewater treatment and help researchers to better understand the potential of CS/MONMs composites for environmental remediation and monitoring. In addition, the challenges of CS/MONM have been proposed.

A review of biosensor for environmental monitoring: principle, application, and corresponding achievement of sustainable development goals

Human health/socioeconomic development is closely correlated to environmental pollution, highlighting the need to monitor contaminants in the real environment with reliable devices such as biosensors. Recently, variety of biosensors gained high attention and employed as in-situ application, in real-time, and cost-effective analytical tools for healthy environment. For continuous environmental monitoring, it is necessary for portable, cost-effective, quick, and flexible biosensing devices. These benefits of the biosensor strategy are related to the Sustainable Development Goals (SDGs) established by the United Nations (UN), especially with reference to clean water and sources of energy. However, the relationship between SDGs and biosensor application for environmental monitoring is not well understood. In addition, some limitations and challenges might hinder the biosensor application on environmental monitoring. Herein, we reviewed the different types of biosensors, principle and applications, and their correlation with SDG 6, 12, 13, 14, and 15 as a reference for related authorities and administrators to consider. In this review, biosensors for different pollutants such as heavy metals and organics were documented. The present study highlights the application of biosensor for achieving SDGs. Current advantages and future research aspects are summarized in this paper.Abbreviations: ATP: Adenosine triphosphate; BOD: Biological oxygen demand; COD: Chemical oxygen demand; Cu-TCPP: Cu-porphyrin; DNA: Deoxyribonucleic acid; EDCs: Endocrine disrupting chemicals; EPA: U.S. Environmental Protection Agency; Fc-HPNs: Ferrocene (Fc)-based hollow polymeric nanospheres; Fe₃O₄@3D-GO: Fe₃O₄@three-dimensional graphene oxide; GC: Gas chromatography; GCE: Glassy carbon electrode; GFP: Green fluorescent protein; GHGs: Greenhouse gases; HPLC: High performance liquid chromatography; ICP-MS: Inductively coupled plasma mass spectrometry; ITO: Indium tin oxide; LAS: Linear alkylbenzene sulfonate; LIG: Laser-induced graphene; LOD: Limit of detection; ME: Magnetoelastic; MFC: Microbial fuel cell; MIP: Molecular imprinting polymers; MWCNT: Multi-walled carbon nanotube; MXC: Microbial electrochemical cell-based; NA: Nucleic acid; OBP: Odorant binding protein; OPs: Organophosphorus; PAHs: Polycyclic aromatic hydrocarbons; PBBs: Polybrominated biphenyls; PBDEs: Polybrominated diphenyl ethers; PCBs: Polychlorinated biphenyls; PGE: Polycrystalline gold electrode; photoMFC: photosynthetic MFC; POPs: Persistent organic pollutants; rGO: Reduced graphene oxide; RNA: Ribonucleic acid; SDGs: Sustainable Development Goals; SERS: Surface enhancement Raman spectrum; SPGE: Screen-printed gold electrode; SPR: Surface plasmon resonance; SWCNTs: single-walled carbon nanotubes; TCPP: Tetrakis (4-carboxyphenyl) porphyrin; TIRF: Total internal reflection fluorescence; TIRF: Total internal reflection fluorescence; TOL: Toluene-catabolic; TPHs: Total petroleum hydrocarbons; UN: United Nations; VOCs: Volatile organic compounds.

Confinement-enhanced microalgal individuals biosensing for digital atrazine assay

Microalgal sensors are widely recognized for their high sensitivity, accessibility, and low cost. However, the current dilemma of motion-induced spatial phase changes and concentration-related multiple scattering interferes with induced test instability and limited sensitivity, which has hindered their practical applications. Here, a differentiated strategy, named confinement-enhanced microalgal biosensing (C-EMB), is developed and proposed to pave the way. The in-situ printed microgel trap is designed to confine Chlamydomonas reinhardtii individuals, stabilizing their spatial phase. The microgel trap arrays are introduced to eliminate the multiple scattering of microalgae, breaking the existing effective concentration in traditional microalgal sensing and enabling sensitive assays. The integration with lab-on-a-chip technology and a developed digital imaging algorithm empower portable and automated detection. With this system, a microalgae analyzer is developed for atrazine detection, featuring a linear range of 0.04-100 μg/L. We assess the system's performance through practical atrazine assays on commercial food, using a double-blind test against a standard instrument. Our results demonstrate the good accuracy and test stability of this system with the mean bias atrazine detection in corn and sugarcane juice samples (SD) were 1.661 μg/L (3.122 μg/L) and 3.144 μg/L (4.125 μg/L), respectively. This method provides a new paradigm of microalgal sensors and should advance the further applications of microalgal sensors in commercial and practical settings.

Smartphone-integrated paper-based biosensor for sensitive fluorometric ethanol quantification

The development of fluorometric paper-based analytical devices (fPADs) integrated with smartphone for fluorometric quantification of ethanol in an instrument-free and portable setup is described. The NAD+-dependent alcohol dehydrogenase immobilized within chitosan modified paper substate was utilized as a bio-recognition element and enzymatically generated NADH was used as a fluorescent probe. 3D-printed imaging setup which houses a paper chip holder and UV-light emitting device (LED) was developed for rapid, accurate capture of the fluorescent images. The biocompatible chitosan layer covering the paper provides a feasible environment for enzyme immobilization and enhances the fluorescence signal. The developed fPADs exhibited high sensitivity for ethanol detection and has a linear range for ethanol detection from 17 µM to 8.75 mM (R2 =0.99). Additionally, the fPADs were applied to quantify ethanol in four different wine samples including red, white, rose, and sparkling wines successfully. Moreover, the fPADs produce reproducible signals without loss of enzyme activity for at least 14 days and ~80% activity remained till 28 days. Thus, the proposed approach can provide a facile, affordable, portable, and instrument-free tool for the onsite quantification of ethanol in real samples and is applicable for food quality controls.

A hypothetical model of multi-layered cost-effective wastewater treatment plant integrating microbial fuel cell and nanofiltration technology: A comprehensive review on wastewater treatment and sustainable remediation

Wastewater management has emerged as an uprising concern that demands immediate attention from environmentalists worldwide. Indiscriminate and irrational release of industrial and poultry wastes, sewage, pharmaceuticals, mining, pesticides, fertilizers, dyes and radioactive wastes, contribute immensely to water pollution. This has led to the aggravation of critical health concerns as evident from the uprising trends of antimicrobial resistance, and the presence of xenobiotics and pollutant traces in humans and animals due to the process of biomagnification. Therefore, the development of reliable, affordable and sustainable technologies for the supply of fresh water is the need of the hour. Conventional wastewater treatment often involves physical, chemical, and biological processes to remove solids from the effluent, including colloids, organic matter, nutrients, and soluble pollutants (metals, organics). Synthetic biology has been explored in recent years, incorporating both biological and engineering concepts to refine existing wastewater treatment technologies. In addition to outlining the benefits and drawbacks of the current technologies, this review addresses novel wastewater treatment techniques, especially those using dedicated rational design and engineering of organisms and their constituent parts. Furthermore, the review hypothesizes designing a multi-bedded wastewater treatment plant that is highly cost-efficient, sustainable and requires easy installation and handling. The novel setup envisages removing all the major wastewater pollutants, providing water fit for household, irrigation and storage purposes.

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.

Fluorescent sensor based on solid-phase extraction with negligible depletion: A proof-of-concept study with amines as analytes

This paper describes the development and proof-of-concept testing of an easy-to-use trace analysis technique, namely F-SPE, by coupling fluorescent sensor with solid phase extraction (SPE). F-SPE is a two-step methodology that concentrates an analyte from a liquid sample onto a fluorophore-modified membrane and measures the amount of analyte from the extent the extracted analyte quenches the emission of the fluorophore. By applying the principle of negligible depletion (ND) intrinsic to SPE, the procedure of F-SPE for analyzing a sample can be markedly simplified while maintaining the ability to detect analytes at low limits of detection (LOD). The merits of this approach are demonstrated by impregnating a SPE membrane with a perylene diimide (PDI) fluorophore, N,N'-di(nonyldecyl)-perylene-3,4,9,10-tetracarboxylic diimide (C9/9-PDI), for the low-level detection of organic amines (e.g., aniline) and amine-containing drugs (e.g., Kanamycin). The sensing mechanism is based on the donor-acceptor quenching of PDI by amines, which, when coupled with the concentrative nature of SPE, yields LODs for aniline and Kanamycin of 67 nM (∼6 ppb) and 32 nM (∼16 ppb), respectively.

Self-assembled monolayer-assisted label-free electrochemical genosensor for specific point-of-care determination of Haemophilus influenzae

For sensitive detection of the L-fuculokinase genome related to the Haemophilus influenzae (H. influenzae), this research work demonstrates the label-free electrochemical-based oligonucleotide genosensing assay relying on the performing hybridization process. To enhance the electrochemical responses, multiple electrochemical modifier-tagged agents were effectively utilized. For attaining this goal, NiCr-layered double hydroxide (NiCr LDH) has been synthesized and combined with biochar (BC) to create an efficient electrochemical signal amplifier that has been immobilized on the surface of the bare Au electrode. Low detection and quantification limits (LOD and LOQ) associated with the designed genosensing bio-platform to detect L-fuculokinase have been achieved to 6.14 fM and 11 fM, respectively. Moreover, the wide linear range of 0.1 to 1000 pM demonstrates the capability of the designed platform. Investigated were the 1-, 2-, and 3-base mismatched sequences, and the negative control samples clarified the high selectivity and better performance of the engineered assay. The values of 96.6-104% and 2.3-3.4% have been obtained for the recoveries and RSDs, respectively. Furthermore, the repeatability and reproducibility of the associated bio-assay have been studied. Consequently, the novel method is appropriate for rapidly and quantitatively detecting H. influenzae, and is considered a better candidate for advanced tests on biological samples such as urine samples.

Closed-loop Control Systems for Pumps used in Portable Analytical Systems

The demand for accurate control of the flowrate/pressure in chemical analytical systems has given rise to the adoption of mechatronic approaches in analytical instruments. A mechatronic device is a synergistic system which combines mechanical, electronic, computer and control components. In the development of portable analytical devices, considering the instrument as a mechatronic system can be useful to mitigate compromises made to decrease space, weight, or power consumption. Fluid handling is important for reliability, however, commonly utilized platforms such as syringe and peristaltic pumps are typically characterized by flow/pressure fluctuations and slow responses. Closed loop control systems have been used effectively to decrease the difference between desired and realized fluidic output. This review discusses the way control systems have been implemented for enhanced fluidic control, categorized by pump type. Advanced control strategies used to enhance the transient and the steady state responses are discussed, along with examples of their implementation in portable analytical systems. The review is concluded with the outlook that the challenge in adequately expressing the complexity and dynamics of the fluidic network as a mathematical model has yielded a trend towards the adoption of experimentally informed models and machine learning approaches.

An Ultrasensitive miRNA-Based Genosensor for Detection of MicroRNA 21 in Gastric Cancer Cells Based on Functional Signal Amplifier and Synthesized Perovskite-Graphene Oxide and AuNPs

In the present research work, the state-of-art label-free electrochemical genosensing platform was developed based on the hybridization process in the presence of [Fe(CN)₆]^3-/4- as an efficient redox probe for sensitive recognition of the miRNA-21 in human gastric cell lines samples. To attain this aim, perovskite nanosheets were initially synthesized. Afterward, the obtained compound was combined with the graphene oxide resulting in an effective electrochemical modifier, which was dropped on the surface of the Au electrode. Then, AuNPs (Gold Nano Particles) have been electrochemically-immobilized on perovskite-graphene oxide/Au-modified electrode surface through the chronoamperometry (CA) technique. Finally, a self-assembling monolayer reaction of ss-capture RNA ensued by the thiol group at the end of the probe with AuNPs on the modified electrode surface. miRNA-21 has been cast on the Au electrode surface to apply the hybridization process. To find out the effectiveness of the synthesized modifier agent, the electrochemical behavior of the modified electrode has been analyzed through DPV (differential pulse voltammetry) and CV (cyclic voltammetry) techniques. The prepared biomarker-detection bioassay offers high sensitivity and specificity, good performance, and appropriate precision and accuracy for the highly-sensitive determination of miRNA-21. Different characterization methods have been used, such as XRD, Raman, EDS, and FE-SEM, for morphological characterization and investigation of particle size. Based on optimal conditions, the limit of detection and quantification have been acquired at 2.94 fM and 8.75 fM, respectively. Furthermore, it was possible to achieve a wide linear range which is between 10^-14 and 10^-7 for miRNA-21. Moreover, the selectivity of the proposed biosensing assay was investigated through its potential in the detection of one, two, and three-base mismatched sequences. Moreover, it was possible to investigate the repeatability and reproducibility of the related bio-assay. To evaluate the hybridization process, it is important that the planned biomarker detection bio-assay could be directly re-used and re-generated.

Colorimetric Cu2+ Detection of (1E,2E)-1,2-Bis((1H-pyrrol-2-yl)methylene)hydrazine Using a Custom-Built Colorimeter

The compound (1E,2E)-1,2-bis((1H-pyrrol-2-yl)methylene)hydrazine (1) was investigated for its chemosensor application. The colorimetric response of 1 with various ions was investigated, and the selective optical change upon mixing with Cu²⁺ was found. The Cu²⁺ binding stoichiometry of 1 derived from Job's plot and the in silico study give us the tentative structural detail of the binding mode of 1 and Cu²⁺ being 1:1. The binding constant between 1 and Cu²⁺ from the Benesi-Hildebrand plot was 1.49 × 10⁴ M^-1. The limit of detection of 1 in Cu²⁺ detection was 0.64 μM (0.040 ppm), which is much lower than the WHO and US EPA maximum allowable Cu²⁺ level in drinking water (2 and 1.3 ppm, respectively). The custom-built colorimeter demonstrates a good linear relationship between Cu²⁺ concentration and electrical resistance (Ω) upon 1-Cu²⁺ ion binding.

Optoelectronic refractometric sensing device for gases based on dielectric bow-ties and amorphous silicon solar cells

The transformation of an hydrogenated amorphous silicon solar cell (aSiH) into an optoelectronic refratometric sensor has been possible through the addition of dielectric bow-tie resonant structures. The indium transparent oxide top electrode is replaced by a thin metallic layer to selectively prevent the direct transmission of light to the active layer of the cell. Then, an array of dielectric bow-tie structures is placed on top of this electrode, to activate the optical absorption through surface plasmon resonance (SPR). The whole device is exposed to the analyte under measure, which is the surrounding medium. Three different dielectric materials with low, medium, and high refractive index were selected for the bow-ties, namely magnesium fluoride (MgF[Formula: see text]), silicon dioxide (SiO[Formula: see text]), and aluminum nitride (AlN) have been tested as coupling structure for SPR excitation. The maximization of the readout/short circuit current has been achieved through the geometrical parameters of such structure. We have selected the geometrical parameters to maximize the short circuit current delivered by the a-Si cell at a given selected wavelength. The design has been customized to gas measurements application, where the index of refraction is slightly above 1 around 10[Formula: see text]. Our analysis reveals ultra-high sensitivity of [Formula: see text] (mA/W)/RIU, and a figure of merit FOM= 107 RIU[Formula: see text], when the bow-tie is made of SiO[Formula: see text]. A performance rally competitive with those previously reported in literature, with the additional advantage of circunventing both moving parts and spectral interrogation elements.

State-of-the-art progress of metal-organic framework-based electrochemical and optical sensing platforms for determination of bisphenol A as an endocrine disruptor

Considering the low concentration levels of bisphenol compounds present in environmental, food, and biological samples, and the difficulty in analyzing the matrices, the main challenge is with the cleanup and extraction process, as well as developing highly sensitive determination methods. Recent advances in the field of metal-organic frameworks (MOFs) due to their large surface area, low weight, and other extraordinary physical, chemical, and mechanical features have made these porous materials a crucial agent in developing biosensing assays. This review focuses on MOFs across their definition, structural features, various types, synthetic routes, and their significant utilization in sensing assays for bisphenol A (BPA) determination. Additionally, recent improvements in characteristics and physio-chemical features of MOFs and their functional applications in developing electrochemical and optical sensing assays via different recognition elements for detecting BPA are comprehensively discussed. Finally, the existing boundaries of the current advances including future challenges concerning successful construction of sensing approaches by employing functionalized MOFs are addressed.

Analytical Chemistry: Tasks, Resolutions and Future Standpoints of the Quantitative Analyses of Environmental Complex Sample Matrices

Currently, the challenges that analytical chemistry has to face are ever greater and more complex both from the point of view of the selectivity of analytical methods and their sensitivity. This is especially true in quantitative analysis, where various methods must include the development and validation of new materials, strategies, and procedures to meet the growing need for rapid, sensitive, selective, and green methods. In this context, given the International Guidelines, which over time, are updated and which set up increasingly stringent “limits”, constant innovation is required both in the pre-treatment procedures and in the instrumental configurations to obtain reliable, accurate, and reproducible information. In addition, the environmental field certainly represents the greatest challenge, as analytes are often present at trace and ultra-trace levels. These samples containing analytes at ultra-low concentration levels, therefore, require very labor-intensive sample preparation procedures and involve the high consumption of organic solvents that may not be considered “green”. In the literature, in recent years, there has been a strong development of increasingly high-performing sample preparation techniques, often “solvent-free”, as well as the development of hyphenated instrumental configurations that allow for reaching previously unimaginable levels of sensitivity. This review aims to provide an update of the most recent developments currently in use in sample pre-treatment and instrument configurations in the environmental field, also evaluating the role and future developments of analytical chemistry in light of upcoming challenges and new goals yet to be achieved.

Flow-Through Acetylcholinesterase Sensor with Replaceable Enzyme Reactor

Fast and reliable determination of enzyme inhibitors are of great importance in environmental monitoring and biomedicine because of the high biological activity and toxicity of such species and the necessity of their reliable assessment in many media. In this work, a flow-through biosensor has been developed and produced by 3D printing from poly(lactic acid). Acetylcholinesterase from an electric eel was immobilized on the inner walls of the reactor cell. The concentration of thiocholine formed in enzymatic hydrolysis of the substrate was monitored amperometrically with a screen-printed carbon electrode modified with carbon black particles, pillar[5]arene, electropolymerized Methylene blue and thionine. In the presence of thiocholine, the cathodic current at −0.25 V decreased because of an alternative chemical reaction of the macrocycle. The conditions of enzyme immobilization and signal measurements were optimized and the performance of the biosensor was assessed in the determination of reversible (donepezil, berberine) and irreversible (carbofuran) inhibitors. In the optimal conditions, the flow-through biosensor made it possible to determine 1.0 nM–1.0 μM donepezil, 1.0 μM–1.0 mM berberine and 10 nM to 0.1 μM carbofuran. The AChE biosensor was tested on spiked samples of artificial urine for drugs and peanuts for carbofuran. Possible interference of the sample components was eliminated by dilution of the samples with phosphate buffer. Easy mounting, low cost of replaceable parts of the cell and satisfactory analytical and metrological characteristics made the biosensor a promising future application as a point-of-care or point-of-demand device outside of a chemical laboratory.

Dual-reverse-signal ratiometric fluorescence method for malachite green detection based on multi-mechanism synergistic effect

The proposition of ratiometric detection mode has demonstrated great superiority in improving analysis accuracy by forming self-calibration. Herein, the novel dual-reverse-signal ratiometric fluorescence detection for malachite green (MG) was first achieved based on synergistic effect of fluorescence resonance energy transfer (FRET) and inner filter effect (IFE). The ratiometric fluorescence probe (B-RCDs) was self-assembled via electrostatic attraction between blue-emission carbon dots (BCDs) and red-emission carbon dots (RCDs), followed with FRET effect from BCDs to RCDs and exhibited dual-emission at 450 nm and 627 nm. In the presence of MG, the IFE effect between MG and RCDs quenched the fluorescence at 627 nm and restored the fluorescence at 450 nm, sending out two reverse signals along with an obvious color change from pink to purple (302 nm UV lamp). This ratiometric method not only simplified the preparation process, but also improved the detection sensitivity, showing a low limit of detection (LOD) of 41.8 nM, which exhibited superiority than that of single-signal RCDs (157.3 nM). This method held a rapid response of 10 min and represented satisfactory recoveries (99.14%-109.08%) in real water samples, revealing it was a promising candidate in the fast, sensitive and practical detection of MG. Moreover, the design of synergistic effect supplied a new perspective for the development of ratiometric sensing in the future.

Recent trends in layered double hydroxides based electrochemical and optical (bio)sensors for screening of emerging pharmaceutical compounds

The rapid expansion of the human population has given rise to new environmental and biomedical concerns, contributing to different advancements in the pharmaceutical industry. In the field of analytical chemistry over the last few years, layered double hydroxides (LDHs) have drawn significant attention, owing to their extraordinary properties. Furthermore, the novel advancement of LDH-based optical and electrochemical platforms to detect different pharmaceutical materials has acquired substantial attention because of their outstanding specificity, actual-time controlling, and user-friendliness. This review aims to recapitulate advanced LDHs-based optical and electrochemical sensors and biosensors to identify and measure important pharmaceutical compounds, such as anti-depressant, anti-inflammatory, anti-viral, anti-bacterial, anti-cancer, and anti-fungal drugs. Additionally, fundamental parameters, namely interactions between sensor and analyte, design rationale, classification, selectivity, and specificity are considered. Finally, the development of high-efficiency techniques for optical and electrochemical sensors and biosensors is featured to deliver scientists and readers a complete toolbox to identify a broad scope of pharmaceutical substances. Our goals are: (i) to elucidate the characteristics and capabilities of available LDHs for the identification of pharmaceutical compounds; and (ii) to deliver instances of the feasible opportunities that the existing devices have for the developed sensing of pharmaceuticals regarding the protection of ecosystems and human health at the global level.

Sustainable Downscaled Catalytic Colorimetric Determination of Manganese in Freshwater Using Smartphone-Based Monitoring Oxidation of 3,3′,5,5′-Tetramethylbenzidine by Periodate

A sustainable downscaled procedure using smartphone-based colorimetric determination of manganese (Mn(II)) was developed. This novel Mn(II) determination procedure is proposed using a simple, available microwell-plate platform and a smartphone as a detector. This approach is based on the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) by periodate using Mn(II) as a catalyst. The catalytic kinetics of Mn(II) under different conditions was investigated to determine the optimum condition where the different catalytic activities of various concentrations of Mn(II) evince. Under the optimum condition, the bluish-green product of oxidized TMB, proportioned to the concentration of Mn(II), was monitored using a smartphone camera, and the color signals were processed using ImageJ Software. The developed procedure showed great selectivity and sensitivity as linearity ranged from 1.8 × 10⁻⁶ to 4.6 × 10⁻⁵ M (0.1 to 2.5 μg/mL). The limits of detection and quantitation were 3.6 × 10⁻⁶ and 1.1 × 10⁻⁵ M (0.2 and 0.6 μg/mL), respectively. The determination of Mn(II) in freshwater samples was demonstrated to assess environmental water quality as an initial model to more easily promote water management according to the United Nations Sustainable Development Goals (UN-SDGs). The intensity of the red could be successfully applied to evaluate Mn(II) in canals and river water with no significant differences compared with the reference method of Inductively Coupled Plasma Optical Emission Spectrometry at a confidence level of 95%.

Recent Advancements in Electrochemical Biosensors for Monitoring the Water Quality

The release of chemicals and microorganisms from various sources, such as industry, agriculture, animal farming, wastewater treatment plants, and flooding, into water systems have caused water pollution in several parts of our world, endangering aquatic ecosystems and individual health. World Health Organization (WHO) has introduced strict standards for the maximum concentration limits for nutrients and chemicals in drinking water, surface water, and groundwater. It is crucial to have rapid, sensitive, and reliable analytical detection systems to monitor the pollution level regularly and meet the standard limit. Electrochemical biosensors are advantageous analytical devices or tools that convert a bio-signal by biorecognition elements into a significant electrical response. Thanks to the micro/nano fabrication techniques, electrochemical biosensors for sensitive, continuous, and real-time detection have attracted increasing attention among researchers and users worldwide. These devices take advantage of easy operation, portability, and rapid response. They can also be miniaturized, have a long-life span and a quick response time, and possess high sensitivity and selectivity and can be considered as portable biosensing assays. They are of special importance due to their great advantages such as affordability, simplicity, portability, and ability to detect at on-site. This review paper is concerned with the basic concepts of electrochemical biosensors and their applications in various water quality monitoring, such as inorganic chemicals, nutrients, microorganisms' pollution, and organic pollutants, especially for developing real-time/online detection systems. The basic concepts of electrochemical biosensors, different surface modification techniques, bio-recognition elements (BRE), detection methods, and specific real-time water quality monitoring applications are reviewed thoroughly in this article.

Review of the Design of Ruthenium-Based Nanomaterials and Their Sensing Applications in Electrochemistry

In this review, ruthenium nanoparticles (Ru NPs)-based functional nanomaterials have attractive electrocatalytic characteristics and they offer considerable potential in a number of fields. Ru-based binary or multimetallic NPs are widely utilized for electrode modification because of their unique electrocatalytic properties, enhanced surface-area-to-volume ratio, and synergistic effect between two metals provides as an effective improved electrode sensor. This perspective review suggests the current research and development of Ru-based nanomaterials as a platform for electrochemical (EC) sensing of harmful substances, biomolecules, insecticides, pharmaceuticals, and environmental pollutants. The advantages and limitations of mono-, bi-, and multimetallic Ru-based nanocomposites for EC sensors are discussed. Besides, the relevant EC properties and analyte sensing approaches are also presented. On the basis of these insights, we highlighted recent results for synthesizing techniques and EC environmental pollutant sensors from the perspectives of diverse supports, including graphene, carbon nanotubes, silica, semiconductors, metal sulfides, and polymers. Finally, this work overviews the modern improvements in the utilization of Ru-based nanocomposites on the basis for electroanalytical sensors as well as suggestions for the field's future development.

Recent Advances in Early Diagnosis of Viruses Associated with Gastroenteritis by Biosensors

Gastroenteritis, as one of the main worldwide health challenges, especially in children, leads to 3–6 million deaths annually and causes nearly 20% of the total deaths of children aged ˂5 years, of which ~1.5 million gastroenteritis deaths occur in developing nations. Viruses are the main causative agent (~70%) of gastroenteritis episodes and their specific and early diagnosis via laboratory assays is very helpful for having successful antiviral therapy and reduction in infection burden. Regarding this importance, the present literature is the first review of updated improvements in the employing of different types of biosensors such as electrochemical, optical, and piezoelectric for sensitive, simple, cheap, rapid, and specific diagnosis of human gastroenteritis viruses. The Introduction section is a general discussion about the importance of viral gastroenteritis, types of viruses that cause gastroenteritis, and reasons for the combination of conventional diagnostic tests with biosensors for fast detection of viruses associated with gastroenteritis. Following the current laboratory detection tests for human gastroenteritis viruses and their limitations (with subsections: Electron Microscope (EM), Cell Culture, Immunoassay, and Molecular Techniques), structural features and significant aspects of various biosensing methods are discussed in the Biosensor section. In the next sections, basic information on viruses causing gastroenteritis and recent developments for fabrication and testing of different biosensors for each virus detection are covered, and the prospect of future developments in designing different biosensing platforms for gastroenteritis virus detection is discussed in the Conclusion and Future Directions section as well.

Paper-based microfluidic colorimetric sensor on a 3D printed support for quantitative detection of nitrite in aquatic environments

To ensure safe drinking water, it is necessary to have a simple method by which the probable pollutants are detected at the point of distribution. Nitrite contamination in water near agricultural locations could be an environmental concern due to its deleterious effects on the human population. The development of a frugal paper-based microfluidic sensor could be desirable to achieve the societal objective of providing safe drinking water. This work describes the development of a facile and cost-effective microfluidic paper-based sensor for quantitative estimation of nitrite in aquatic environments. A simple punching machine was used for fabrication and rapid prototyping of paper-based sensors without the need of any specialized equipment or patterning techniques. A reusable 3D printed platform served as the support for simultaneous testing of multiple samples. The nitrite estimation was carried out with smartphone-assisted digital image acquisition and colorimetric analysis. Under optimized experimental conditions, the variation in average grayscale intensity with concentration of nitrite was linear in the range from 0.1 to 10 ppm. The limits of detection and quantitation were 0.12 ppm and 0.35 ppm respectively. The reproducibility, expressed as relative standard deviation was 1.31%. The selectivity of nitrite detection method was determined by performing interference studies with commonly existing co-ions in water, such as bicarbonates, chloride and sulphate. The paper-based sensor was successfully applied for estimation of nitrite in actual water samples and showed high recoveries in the range of 83.5-109%. The results were in good agreement with those obtained using spectrophotometry. The developed paper-based sensor method, by virtue of its simplicity, ease of fabrication and use, could be readily extended for detection of multiple analytes in resource-limited settings.

Genosensors as an alternative diagnostic sensing approaches for specific detection of various certain viruses: a review of common techniques and outcomes

Viral infections are responsible for the deaths of millions of people throughout the world. Since outbreak of highly contagious and mutant viruses such as contemporary sars-cov-2 pandemic, has challenged the conventional diagnostic methods, the entity of a thoroughly sensitive, specific, rapid and inexpensive detecting technique with minimum level of false-positivity or -negativity, is desperately needed more than any time in the past decades. Biosensors as minimized devices could detect viruses in simple formats. So far, various nucleic acid, immune- and protein-based biosensors were designed and tested for recognizing the genome, antigen, or protein level of viruses, respectively; however, nucleic acid-based sensing techniques, which is the foundation of constructing genosensors, are preferred not only because of their ultra-sensitivity and applicability in the early stages of infections but also for their ability to differentiate various strains of the same virus. To date, the review articles related to genosensors are just confined to particular pathogenic diseases; In this regard, the present review covers comprehensive information of the research progress of the electrochemical, optical, and surface plasmon resonance (SPR) genosensors that applied for human viruses' diseases detection and also provides a well description of viruses' clinical importance, the conventional diagnosis approaches of viruses and their disadvantages. This review would address the limitations in the current developments as well as the future challenges involved in the successful construction of sensing approaches with the functionalized nanomaterials and also allow exploring into core-research works regarding this area.

The status of potable water reuse implementation

A review of the current status of direct and indirect potable water reuse (DPR/IPR) implementation has been conducted, focusing on the regulatory and practical aspects and with reference to the most recent published literature. The review encompasses (a) the principal contaminant types, their required removal and the methods by which their concentration is monitored, (b) regulatory approaches and stipulations in assessing/ratifying treatment schemes and maintaining treated water quality, and (c) existing full-scale installations. Analytical methods discussed include established in-line monitoring tools, such as turbidity measurement, to more recent polymerase chain reaction (PCR)-based assay methods for microbial detection. The key risk assessment tools of quantitative microbial risk assessment (QMRA) and water safety plans (WSPs) are considered in relation to their use in selecting/ratifying treatment schemes, and the components of the treatment schemes from 40 existing IPR/DPR installations summarised. Five specific schemes are considered in more detail. The review reveals:Whilst there are a number of ongoing projects where RO is not used because of the challenge imposed by disposal of RO concentrate, the prevalence of the sequential RO-UV combination implies the importance of quantifying the impact of process upsets on these unit operations.

Interfacing Machine Learning and Microbial Omics: A Promising Means to Address Environmental Challenges

Microbial communities are ubiquitous and carry an exceptionally broad metabolic capability. Upon environmental perturbation, microbes are also amongst the first natural responsive elements with perturbation-specific cues and markers. These communities are thereby uniquely positioned to inform on the status of environmental conditions. The advent of microbial omics has led to an unprecedented volume of complex microbiological data sets. Importantly, these data sets are rich in biological information with potential for predictive environmental classification and forecasting. However, the patterns in this information are often hidden amongst the inherent complexity of the data. There has been a continued rise in the development and adoption of machine learning (ML) and deep learning architectures for solving research challenges of this sort. Indeed, the interface between molecular microbial ecology and artificial intelligence (AI) appears to show considerable potential for significantly advancing environmental monitoring and management practices through their application. Here, we provide a primer for ML, highlight the notion of retaining biological sample information for supervised ML, discuss workflow considerations, and review the state of the art of the exciting, yet nascent, interdisciplinary field of ML-driven microbial ecology. Current limitations in this sphere of research are also addressed to frame a forward-looking perspective toward the realization of what we anticipate will become a pivotal toolkit for addressing environmental monitoring and management challenges in the years ahead.

Enzymeless voltammetric sensor for simultaneous determination of parathion and paraoxon based on Nd-based metal-organic framework

The aim of this work is to fabricate a sensitive and novel enzymeless electrochemical sensor for the simultaneous determination of parathion and paraoxon using the Nd-UiO-66@MWCNT nanocomposite. For this purpose, Neodymium (Nd) was introduced into a Universitetet i Oslo (UiO-66) structure to construct Nd-UiO-66 and then, adding multi-walled carbon nanotubes to the Nd-UiO-66 to increase the electrocatalytic activity and surface area of the obtained composite. The Nd-UiO-66@MWCNT has numerous advantages like excellent conductivity, tunable texture, and large surface area and can be used as a distinctive structure for the construction of modified glassy carbon electrode (GCE) to enhance the charge-transfer and the efficiency of electrochemical sensors. This modified electrode showed sensitive and selective determination of paraoxon and parathion over the linear ranges of 0.7-100 and 1-120 nM, with detection limits of 0.04 and 0.07 nM, respectively. The proposed Nd-UiO-66@MWCNT/GCE sensor in this study can be applied in environmental and toxicological laboratories and field tests to detect parathion and paraoxon levels.

Recent advances in the highly sensitive determination of zearalenone residues in water and environmental resources with electrochemical biosensors

Zearalenone (ZEN), a significant class of mycotoxin which is considered as a xenoestrogen, permits, similar to natural estrogens, it's binding to the receptors of estrogen resulting in various reproductive diseases especially, hormonal misbalance. ZEN has toxic effects on human and animal health as a result of its teratogenicity, carcinogenicity, mutagenicity, nephrotoxicity, genotoxicity, and immunotoxicity. To ensure water and environmental resources safety, precise, rapid, sensitive, and reliable analytical and conventional methods can be progressed for the determination of toxins such as ZEN. Different selective nanomaterial-based compounds are used in conjunction with different analytical detection approaches to achieve this goal. The current review demonstrates the state-of-the-art advances of nanomaterial-based electrochemical sensing assays including various sensing, apta-sensing and, immunosensing studies to the highly sensitive determination of various ZEN families. At first, a concise study of the occurrence, structure, toxicity, legislations, and distribution of ZEN in monitoring has been performed. Then, different conventional and clinical techniques and procedures to sensitive and selective sensing techniques have been reviewed and the efficient comparison of them has been thoroughly discussed. This study has also summarized the salient features and the requirements for applying various sensing and biosensing platforms and diverse immobilization techniques in ZEN detection. Finally, we have defined the performance of several electrochemical sensors applying diverse recognition elements couples with nanomaterials fabricated using various recognition elements coupled with nanomaterials (metal NPs, metal oxide nanoparticles (NPs), graphene, and CNT) the issues limiting development, and the forthcoming tasks in successful construction with the applied nanomaterials.

State of the art: Lateral flow assays toward the point-of-care foodborne pathogenic bacteria detection in food samples

Diverse chemicals and some physical phenomena recently introduced in nanotechnology have enabled scientists to develop useful devices in the field of food sciences. Concerning such developments, detecting foodborne pathogenic bacteria is now an important issue. These kinds of bacteria species have demonstrated severe health effects after consuming foods and high mortality related to acute cases. The most leading path of intoxication and infection has been through food matrices. Hence, quick recognition of foodborne bacteria agents at low concentrations has been required in current diagnostics. Lateral flow assays (LFAs) are one of the urgent and prevalently applied quick recognition methods that have been settled for recognizing diverse types of analytes. Thus, the present review has stressed on latest developments in LFAs-based platforms to detect various foodborne pathogenic bacteria such as Salmonella, Listeria, Escherichia coli, Brucella, Shigella, Staphylococcus aureus, Clostridium botulinum, and Vibrio cholera. Proper prominence has been given on exactly how the labels, detection elements, or procedures have affected recent developments in the evaluation of diverse bacteria using LFAs. Additionally, the modifications in assays specificity and sensitivity consistent with applied food processing techniques have been discussed. Finally, a conclusion has been drawn for highlighting the main challenges confronted through this method and offered a view and insight of thoughts for its further development in the future.