Biosensor for heavy metals detection in wastewater: A review

Engineering two-component systems for advanced biosensing: From architecture to applications in biotechnology

Two-component systems (TCSs) are prevalent signaling pathways in bacteria. These systems mediate phosphotransfer between histidine kinase and a response regulator, facilitating responses to diverse physical, chemical, and biological stimuli. Advancements in synthetic and structural biology have repurposed TCSs for applications in monitoring heavy metals, disease-associated biomarkers, and the production of bioproducts. However, the utility of many TCS biosensors is hindered by undesired performance due to the lack of effective engineering methods. Here, we briefly discuss the architectures and regulatory mechanisms of TCSs. We also summarize the recent advancements in TCS engineering by experimental or computational-based methods to fine-tune the biosensor functional parameters, such as response curve and specificity. Engineered TCSs have great potential in the medical, environmental, and biorefinery fields, demonstrating a crucial role in a wide area of biotechnology.

Indirect detection of lead(II), cadmium(II) and mercury(II) on a microfluidic electrophoresis chip

Water environments contaminated by heavy metal ions present significant challenges because these pollutants do not degrade naturally, leading to their gradual bioaccumulation in animals and plants, which ultimately poses an insurmountable threat to human health. Therefore, rapid and accurate detection of heavy metal ions in water is of great significance for environmental protection and disease prevention. In this work, we developed a novel method based on microfluidic electrophoresis coupled with indirect chemiluminescence for the immediate detection of Cd(II), Pb(II) and Hg(II) heavy metal ions. The displacement of the Co(II) ions within the chemiluminescence mixture by the above migrating sample cations caused a measurable reduction in the background signal. The results showed that the detection limits of Cd(II), Pb(II) and Hg(II) ions under the best detection conditions were 5.83 × 10-8 M, 5.38 × 10-8 M and 2.09 × 10-8 M, respectively, which were 1-2 orders of magnitude lower than those of the indirect UV method and 1 order of magnitude lower than that of the indirect laser induced detection method. This method can provide a possibility for the rapid detection of multiple heavy metal ions in actual water environments.

Photoresponsive metal-organic framework materials for advance applications

The interaction between light and materials produces a range of phenomena within molecular systems, leading to advanced applications in the field of materials science. In this regard, metal-organic framework (MOF) materials have become superior candidates to others because of their easy tailor-made synthetic methods via incorporation of photoactive moieties into their structural assembly. Photoresponsive MOFs exhibit a massive variety of exciting properties, including photochromism, photomagnetism, photoluminescence, photon up or down conversion, photoconductivity, nonlinear optical properties, photosalient effects and photoinduced switching of conformations. These photoresponsive properties of MOFs regulate different potential applications, such as on-demand gas sorption and separation, optical sensing, fabrication of photoactuators and photosensing electronic devices, dye degradation, catalysis, cargo delivery, ink-free erasable printing, bio-imaging and drug delivery in biological systems. Therefore, judicious crystal engineering along with an understanding of their structure-property relationship will lead to the fabrication of desired photosensitive MOFs. Herein, we attempted to incorporate categorical descriptions based on advanced applications of photoresponsive MOFs considering a wide range of recent publications.

Graphene Multiplexed Sensor for Point-of-Need Viral Wastewater-Based Epidemiology

Wastewater-based epidemiology (WBE) can help mitigate the spread of respiratory infections through the early detection of viruses, pathogens, and other biomarkers in human waste. The need for sample collection, shipping, and testing facilities drives up the cost of WBE and hinders its use for rapid detection and isolation in environments with small populations and in low-resource settings. Given the ubiquitousness and regular outbreaks of respiratory syncytial virus, SARS-CoV-2, and various influenza strains, there is a rising need for a low-cost and easy-to-use biosensing platform to detect these viruses locally before outbreaks can occur and monitor their progression. To this end, we have developed an easy-to-use, cost-effective, multiplexed platform able to detect viral loads in wastewater with several orders of magnitude lower limit of detection than that of mass spectrometry. This is enabled by wafer-scale production and aptamers preattached with linker molecules, producing 44 chips at once. Each chip can simultaneously detect four target analytes using 20 transistors segregated into four sets of five for each analyte to allow for immediate statistical analysis. We show our platform's ability to rapidly detect three virus proteins (SARS-CoV-2, RSV, and Influenza A) and a population normalization molecule (caffeine) in wastewater. Going forward, turning these devices into hand-held systems would enable wastewater epidemiology in low-resource settings and be instrumental for rapid, local outbreak prevention.

Wastewater-borne viruses and bacteria, surveillance and biosensors at the interface of academia and field deployment

Wastewater is a complex, but an ideal, matrix for disease monitoring and surveillance as it represents the entire load of enteric pathogens from a local catchment area. It captures both clinical and community disease burdens. Global interest in wastewater surveillance has been growing rapidly for infectious diseases monitoring and for providing an early warning of potential outbreaks. Although molecular detection methods show high sensitivity and specificity in pathogen monitoring from wastewater, they are strongly limited by challenges, including expensive laboratory settings and prolonged sample processing and analysis. Alternatively, biosensors exhibit a wide range of practical utility in real-time monitoring of biological and chemical markers. However, field deployment of biosensors is primarily challenged by prolonged sample processing and pathogen concentration steps due to complex wastewater matrices. This review summarizes the role of wastewater surveillance and provides an overview of infectious viral and bacterial pathogens with cutting-edge technologies for their detection. It emphasizes the practical utility of biosensors in pathogen monitoring and the major bottlenecks for wastewater surveillance of pathogens, and overcoming approaches to field deployment of biosensors for real-time pathogen detection. Furthermore, the promising potential of novel machine learning algorithms to resolve uncertainties in wastewater data is discussed.

Recent developments of (bio)-sensors for detection of main microbiological and non-biological pollutants in plastic bottled water samples: A critical review

The importance of water in all biological processes is undeniable. Ensuring access to clean and safe drinking water is crucial for maintaining sustainable water resources. To elaborate, the consumption of water of inadequate quality can have a repercussion on human health. Furthermore, according to the instability of tap water quality, the consumption rate of bottled water is increasing every day at the global level. Although most people believe bottled water is safe, it can also be contaminated by microbiological or chemical pollution, which can increase the risk of disease. Over the last decades, several conventional analytical tools applied to analyze the contamination of bottled water. On the other hand, some limitations restrict their application in this field. Therefore, biosensors, as emerging analytical method, attract tremendous attention for detection both microbial and chemical contamination of bottled water. Biosensors enjoy several facilities including selectivity, affordability, and sensitivity. In this review, the developed biosensors for analyzing contamination of bottled water were highlighted, as along with working strategies, pros and cons of studies. Challenges and prospects were also examined.

Synthesis of zeolite from industrial wastes: a review on characterization and heavy metal and dye removal

Increasing world population, urbanization, and industrialization have led to an increase in demand in production and consumption, resulting in an increase in industrial solid wastes and pollutant levels in water. These two main consequences have become global problems. The high Si and Al content of solid wastes suggests that they can be used as raw materials for the synthesis of zeolites. In this context, when the literature studies conducted to obtain synthetic zeolites are evaluated, it is seen that hydrothermal synthesis method is generally used. In order to improve the performance of the hydrothermal synthesis method in terms of energy cost, synthesis time, and even product quality, additional methods such as alkaline fusion, ultrasonic effect, and microwave support have been developed. The zeolites synthesized by different techniques exhibit superior properties such as high surface area and well-defined pore sizes, thermal stability, high cation exchange capacity, high regeneration ability, and catalytic activity. Due to these specific properties, zeolites are recognized as one of the most effective methods for the removal of pollutants. The toxic properties of heavy metals and dyes in water and their carcinogenic effects in long-term exposure pose a serious risk to living organisms. Therefore, they should be treated at specified levels before discharge to the environment. In this review study, processes including different methods developed for the production of zeolites from industrial solid wastes were evaluated. Studies using synthetic zeolites for the removal of high levels of health and environmental risks such as heavy metals and dyes are reviewed. In addition, EPMA, SEM, EDX, FTIR, BET, AFM, and 29Si and 27Al NMR techniques, which are characterization methods of synthetic zeolites, are presented and the cation exchange capacity, thermodynamics of adsorption, effect of temperature, and pH are investigated. It is expected that energy consumption can be reduced by large-scale applications of alternative techniques developed for zeolite synthesis and their introduction into the industry. It is envisaged that zeolites synthesized by utilizing wastes will be effective in obtaining a green technology. The use of synthesized zeolites in a wide variety of applications, especially in environmental problems, holds great promise.

High-throughput screening of human mercury exposure based on a low-cost naked eye-recognized biosensing platform

Whole-cell biosensors could be helpful for in situ disease diagnosis. However, their use in analyzing biological samples has been hindered by unstable responses, low signal enhancement, and growth inhibition in complex media. Here, we offered a solution by building a visual whole-cell biosensor for urinary mercury determination. With deoxyviolacein as the preferred signal for the mercury biosensor for the first time, it enabled the quantitative detection of urinary mercury with a favorable linear range from 1.57 to 100 nM. The biosensor can accurately diagnose urine mercury levels exceeding the biological exposure index with 95.8% accuracy. Thus, our study provided a biosensing platform with great potential to serve as a stable, user-friendly, and high-throughput alternative for the daily monitoring or estimating of urinary mercury.

Extremozyme-Based Biosensors for Environmental Pollution Monitoring: Recent Developments

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

Development of smartphone-controlled and machine-learning-powered integrated equipment for automated detection of bioavailable heavy metals in soils

Rapid and accurate on-site detection of crop-absorbable cadmium (Cd) and lead (Pb) in soils is important for food security and human health. The automated soil sample pretreatment method, including the ultrasonic extraction of weakly acid-soluble heavy metals, suction-filtration, and UV photolysis, was proposed to achieve the high-efficiency preparation from soil sample to extract solution. Bismuth-film-modified glass carbon electrode combined with the homemade potentiostat was fabricated to implement the square-wave anodic stripping voltammetry (SWASV) measurements of soil extracts. The peak-information-acquisition algorithm was designed to automatically obtain peak heights and widths of Zn2+, Cd2+, Pb2+, Bi3+, and Cu2+ stripping currents, and then which were used as input variables for establishing machine-learning models to enhance the detection accuracy of SWASV to Cd2+ and Pb2+ under the coexistence of multiple heavy metal ions. Eventually, the smartphone-controlled integrated-automated detection equipment was developed and successfully applied to the automatic pretreatment of soil samples and the determination of weakly acid-soluble Cd2+ and Pb2+ in real soil samples. The detection speed was 75 min/sample, and the detection results were close to the standard method (BCR-ICP-MS). This equipment can provide powerful technical support for on-site rapid and accurate determination of crop-absorbable heavy metals in soils.

Biosensing of DNA through difference in interaction between microparticle and glass plate based on particle dissociation in a coupled acoustic-gravitational field

A novel approach for detecting DNA without labeling the target DNA was developed based on the particle dissociation behavior in a combined acoustic-gravitational field. The particles, which are tethered on a glass plate via intermolecular interactions (Fbind), are dissociated by the resultant force of the acoustic radiation force (Fac), which is a function of the applied voltage (V), and the sedimentation force. In this system, V required for particle dissociation is dependent on Fbind. The differences in Fbind were exploited for detecting the target DNA. A glass plate and polystyrene (PS) particles were respectively modified with anchor and capture DNAs. The target DNA induces immobilization of the PS particles on the glass plate through sandwich hybridization, with a large accompanying Fbind. In the absence of the target DNA, the anchor DNA on the glass plate interacted weakly with the capture DNA on the PS particles via direct binding (small Fbind). The particle dissociation behavior varies based on the concentration of the target DNA due to changes in the ratio of the PS particles tethered through direct binding and sandwich hybridization. Target DNA with a length exceeding 12 base pairs (bps) can be detected on the picomolar scale at concentrations of 10-12 to 10-5 M. This detection scheme was applied to a specific sequence of HIV-2 with 20 bps, achieving a picomolar detection limit.

A review on the potential risks and mechanisms of heavy metal exposure to Chronic Obstructive Pulmonary Disease

Chronic Obstructive Pulmonary Disease (COPD) is a chronic disease that affects patients as well as the health and economic stability of society as a whole. At the same time, heavy metal pollution is widely recognized as having a possible impact on the environment and human health. Therefore, these diseases have become important global public health issues. In recent years, researchers have shown great interest in the potential association between heavy metal exposure and the development of COPD, and there has been a substantial increase in the number of related studies. However, we still face the challenge of developing a comprehensive and integrated understanding of this complex association. Therefore, this review aimed to evaluate the existing epidemiological studies to clarify the association between heavy metal exposure and COPD. In addition, we will discuss the biological mechanisms between the two to better understand the multiple molecular pathways and possible mechanisms of action involved, and provide additional insights for the subsequent identification of potential strategies to prevent and control the effects of heavy metal exposure on the development of COPD in individuals and populations.

A Comparison of a Conventional Chemical Coagulant and a Natural Coagulant Derived from Cassia fistula Seeds for the Removal of Heavy Metal Ions

Cassia fistula seed-derived coagulant has been reported to exhibit high coagulating-flocculating activity, environmental friendliness, and cost-effectiveness for the wastewater treatment, especially of textile wastewater. For heavy metal removal, however, research focusing on evaluating the feasibility of this material is still limited. Therefore, this study reports jar-test experiments in which the Zn2+ and Ni2+ removal efficiency of C. fistula coagulant was assessed. Moreover, a comparison of coagulation performance using a conventional chemical coagulant and the natural coagulant was performed. Characterization of the C. fistula seed-derived coagulant revealed the presence of important functional groups and fibrous networks with rough surfaces. A bench-scale study indicated that the coagulation performance of the two coagulants depends strongly on the initial concentration of metal ions, pH level, and coagulant dosage. The C. fistula seed-derived coagulant was found to possess higher removal efficiency than polyaluminum chloride. This natural coagulant removed over 80% of metal ions at the optimal conditions of pH 5.0, a metal ion concentration of 25 ppm, and a dosage of 0.8 and 1.6 g/L for Zn2+ and Ni2+, respectively. This study shows that C. fistula seed-derived coagulant is a potential alternative to chemical coagulants and could be developed to provide an environmentally friendly, economical, and efficient wastewater treatment.

MicroRNA: A Dynamic Player from Signalling to Abiotic Tolerance in Plants

MicroRNAs (miRNAs) are a class of non-coding single-stranded RNA molecules composed of approximately 20-24 nucleotides in plants. They play an important regulatory role in plant growth and development and as a signal in abiotic tolerance. Some abiotic stresses include drought, salt, cold, high temperature, heavy metals and nutritional elements. miRNAs affect gene expression by manipulating the cleavage, translational expression or DNA methylation of target messenger RNAs (mRNAs). This review describes the current progress in the field considering two aspects: (i) the way miRNAs are produced and regulated and (ii) the way miRNA/target genes are used in plant responses to various abiotic stresses. Studying the molecular mechanism of action of miRNAs' downstream target genes could optimize the genetic manipulation of crop growth and development conditions to provide a more theoretically optimized basis for improving crop production. MicroRNA is a novel signalling mechanism in interplant communication relating to abiotic tolerance.

Synthetic bacteria for the detection and bioremediation of heavy metals

Toxic heavy metal accumulation is one of anthropogenic environmental pollutions, which poses risks to human health and ecological systems. Conventional heavy metal remediation approaches rely on expensive chemical and physical processes leading to the formation and release of other toxic waste products. Instead, microbial bioremediation has gained interest as a promising and cost-effective alternative to conventional methods, but the genetic complexity of microorganisms and the lack of appropriate genetic engineering technologies have impeded the development of bioremediating microorganisms. Recently, the emerging synthetic biology opened a new avenue for microbial bioremediation research and development by addressing the challenges and providing novel tools for constructing bacteria with enhanced capabilities: rapid detection and degradation of heavy metals while enhanced tolerance to toxic heavy metals. Moreover, synthetic biology also offers new technologies to meet biosafety regulations since genetically modified microorganisms may disrupt natural ecosystems. In this review, we introduce the use of microorganisms developed based on synthetic biology technologies for the detection and detoxification of heavy metals. Additionally, this review explores the technical strategies developed to overcome the biosafety requirements associated with the use of genetically modified microorganisms.

Polymeric Micellar Systems-A Special Emphasis on "Smart" Drug Delivery

Concurrent developments in anticancer nanotechnological treatments have been observed as the burden of cancer increases every year. The 21st century has seen a transformation in the study of medicine thanks to the advancement in the field of material science and nanomedicine. Improved drug delivery systems with proven efficacy and fewer side effects have been made possible. Nanoformulations with varied functions are being created using lipids, polymers, and inorganic and peptide-based nanomedicines. Therefore, thorough knowledge of these intelligent nanomedicines is crucial for developing very promising drug delivery systems. Polymeric micelles are often simple to make and have high solubilization characteristics; as a result, they seem to be a promising alternative to other nanosystems. Even though recent studies have provided an overview of polymeric micelles, here we included a discussion on the "intelligent" drug delivery from these systems. We also summarized the state-of-the-art and the most recent developments of polymeric micellar systems with respect to cancer treatments. Additionally, we gave significant attention to the clinical translation potential of polymeric micellar systems in the treatment of various cancers.

A recent advancement on the applications of nanomaterials in electrochemical sensors and biosensors

Industrialization and globalization, both on an international and local scale, have caused large quantities of toxic chemicals to be released into the environment. Thus, developing an environmental pollutant sensor platform that is sensitive, reliable, and cost-effective is extremely important. In current years, considerable progress has been made in the expansion of electrochemical sensors and biosensors to monitor the environment using nanomaterials. A large number of emerging biomarkers are currently in existence in the biological fluids, clinical, pharmaceutical and bionanomaterial-based electrochemical biosensor platforms have drawn much attention. Electrochemical systems have been used to detect biomarkers rapidly, sensitively, and selectively using biomaterials such as biopolymers, nucleic acids, proteins etc. In this current review, several recent trends have been identified in the growth of electrochemical sensor platforms using nanotechnology such as carbon nanomaterials, metal oxide nanomaterials, metal nanoparticles, biomaterials and polymers. The integration strategies, applications, specific properties and future projections of nanostructured materials for emerging progressive sensor platforms are also observed. The objective of this review is to provide a comprehensive overview of nanoparticles in the field of electrochemical sensors and biosensors.