3D metal-organic framework as highly efficient biosensing platform for ultrasensitive and rapid detection of bisphenol A

Exploring the potential of metal-organic framework based composites as key players in bisphenol detection

The extensive usage of bisphenols in the production of plastics and other materials has raised concerns about their potential adverse effects on human and marine ecosystems. This comprehensive review paper aims to provide insights into the various types of bisphenols and their derivatives, as well as the multiple pathways through which human and marine life can be exposed to these compounds. Additionally, it highlights the growing importance of developing effective detection methods for bisphenols and their derivatives due to their potential health and environmental implications. The focus then shifts towards metal-organic frameworks (MOFs) as promising materials for the detection of bisphenols. We delve into the characteristic properties of MOFs and their potential and limitations in the detection of bisphenols and their derivatives. This paper also addresses the significance of pristine MOFs and explores the potential of MOF-based composites for achieving enhanced detection performance. Subsequently, various detection techniques utilizing MOFs and their composites are reviewed. In the final sections, the recent strategic developments and challenges in this field, offering a concise summary of the principal findings of this review, novel approaches, limitations of current methodologies, and emerging trends for future directions, are discussed. This comprehensive exploration of the subject matter not only illuminates the current state of research on the detection of bisphenols but also provides valuable insights into the opportunities and challenges in this evolving field. In conclusion, this review underscores the critical importance of advancing the detection of bisphenols and their derivatives, with MOFs and their composites emerging as promising candidates for more efficient and sensitive detection. The potential for their applications in diverse fields, coupled with ongoing research efforts, suggests a bright future for MOF-based bisphenol detection technologies.

Redefining Metal Organic Frameworks in Biosensors: Where Are We Now?

As a broad class of porous nanomaterials, metal organic frameworks (MOFs) exhibit unique properties, such as broad tunability, high stability, atomically well-defined structure, and ordered uniform porosity. These features facilitate the rational design of MOFs as an outstanding nanomaterial candidate in biosensing, therapeutics delivery, and catalysis applications. Recently, novel modifications of the MOF nanoarchitecture and incorporation of synergistic guest materials have been investigated to achieve well-tailored functional design, gradually bridging the fundamental gap between structure and targeted activity. Specifically, the burgeoning studies of MOF-based high-performance biosensors have aimed to achieve high sensitivity, selectivity, and stability for a large variety of analytes in different sensing matrices. In this review, we elaborate the key roles of MOF nanomaterials in biosensors, including their high stability as a protective framework for biomolecules, their intrinsic sensitivity-enhancing functionalities, and their contribution of catalytic activity as a nanozyme. By examining the main structures of MOFs, we further identify varied structural engineering approaches, such as precursor tuning and guest molecule incorporation, that elucidate the concept of the structure-activity relationship of MOFs. Furthermore, we highlight the unique applications of MOF nanomaterials in electrochemical and optical biosensors for enhanced sensor performances. Finally, the challenges and future perspectives of developing next-generation MOF nanomaterials for biosensor applications are discussed.

A novel triple-signal biosensor based on ZrFe-MOF@PtNPs for ultrasensitive aflatoxins detection

The development of more sensitive, stable, and portable biosensors is crucial for meeting the growing demands of diverse and complex detection environments. MOF-based nanozymes have emerged as excellent optical reporters, making them ideal signal donors for constructing multi-signal lateral flow immunoassays (LFIA). In this study, a ZrFe-MOF@PtNPs nanocomposite was synthesized by uniformly depositing platinum nanoparticles (PtNPs) onto the surface of ZrFe-MOFs using an impregnation-reduction method. The ZrFe-MOF@PtNPs exhibited broad absorption spectra, excellent peroxidase-like activity (SA = 21.77 U/mg), high solvent stability, and efficient antibody binding capability. A portable LFIA platform was developed based on ZrFe-MOF@PtNPs and a smartphone for the targeted detection of carcinogenic aflatoxins. This method enabled the readout of colorimetric, fluorescent, and catalytic signals, significantly enhancing detection sensitivity, ensuring result accuracy, and expanding the dynamic detection range. For aflatoxin M1, the calculation of the detection limit of the three signal modes reached as low as 0.0062 ng/mL, which is two orders of magnitude more sensitive than AuNPs-LFIA (0.1839 ng/mL). This study provides effective guidance for multifunctional modification of MOFs and serves as a reference for the application of MOF-based nanozymes in point-of-care biosensors.

Recent advances on metal-organic framework-based electrochemical sensors for determination of organic small molecules

Metal-organic frameworks (MOFs) are an extraordinarily versatile class of porous materials renowned for their intricate three-dimensional skeletal architectures and exceptional chemical properties. These extraordinary attributes have pushed MOFs into the vanguard of diverse disciplines such as microporous conduction, catalysis, separation, biomedical engineering, and electrochemical sensing. The focus of this review is to offer a comprehensive summary of recent advancements in designing MOF-based electrochemical sensors for detecting organic small molecules. offer a comprehensive survey of the recent progress in the methodologies adopted for the construction of MOF composites, covering template-assisted synthesis, Modification in synthesis, and post-synthesis modification. In addition, we discuss the practical application of MOF-based electrochemical sensors in the detection of organic small molecules. Our findings highlight the superior electrochemical sensing capabilities of these novel composites compared to those of their pristine counterparts. In conclusion, we provide a condensed perspective on the potential future trajectories in this domain, underscoring the impetus for continued enquiry and enhancement of MOF composite assemblies. With sustained investigation, the horizon appears bright for electrochemical sensing of small organic molecules and their myriad applications.

Development of Functional Biointerface Using Mixed Zwitterionic Silatranes

Strategies to design multifunctional interfaces for biosensors have been extensively investigated to acquire optimal sensitivity, specificity, and accuracy. However, heterogeneous ingredients in clinical samples inevitably generate background signals, exposing challenges in biosensor performance. Polymer coating has been recognized as a crucial method to functionalize biointerfaces by providing tailored properties that are essential for interacting with biological systems. Herein, we introduce for the first time two oligomeric silatranes, MPS-MPCn and MPS-PEGMACOOHm, which were copolymerized from mercaptopropylsilatrane (MPS) with either zwitterionic monomer 2-methacryloyloxyethyl phosphorylcholine (MPC) or carboxylated poly(ethylene glycol) methacrylate (PEGMACOOH) through thiol-ene polymerization. These oligomeric silatranes were prepared individually and in combinations in acidic and nonacid solvents for deposition on silicon wafers. Afterward, coating properties, including wettability, thickness, and elemental composition, were characterized by contact angle meter, ellipsometer, and X-ray photoelectron spectroscopy (XPS), respectively. Importantly, MPS-MPCn polymers were found to form thin films with high hydrophilicity and superior fouling repulsion to bacteria and protein, while mixed coating involving 70% MPS-PEGMACOOH2.5 and 30% MPS-MPC2.5 exhibited thinnest coating with best wettability among COOH-terminated coatings. Furthermore, the functional COOH group in the coated surfaces was exploited for postmodification with biological molecules via intermediated N-hydroxysuccinimide (NHS) ester group by amine coupling chemistry. Once again, the combination of 70% MPS-PEGMACOOH2.5 and 30% MPS-MPC2.5 provided an ultimate reduction in nonspecific adsorption (NSA) and established a finest signal discrimination through enzyme-linked immunosorbent assay. Consequently, these novel mixed oligomeric silatranes offer a promising approach for the construction of biosensor interfaces with dual functions in both nonspecific binding prevention and conjugation of biomolecules.

When microplastics/plastics meet metal-organic frameworks: turning threats into opportunities

Significant efforts have been devoted to removal and recycling of microplastics (MPs; <5 mm) to address the environmental crises caused by their ubiquitous presence and improper treatment. Metal-organic frameworks (MOFs) demonstrate compatibility with MPs/plastics through adsorption, degradation, or assembly with the MPs/plastic polymers. Above 90% of MPs/plastic particles can be adsorbed on MOF materials via the hydrophobic interaction, electrical attraction, π-π stacking, and van der Waals forces. Meanwhile, certain MOFs have successfully converted various types of plastics into high-valued small molecules through thermocatalysis and photocatalysis. In thermocatalysis, the primary process should be C-O bond cleavage, whereas in photocatalysis it ought to be the generation of reactive oxygen species (ROS). Moreover, the construction of novel MOFs using waste MPs/plastics as the ligands was mostly accomplished through three dominant ways, including glycolysis, hydrolysis and methanolysis. Once successfully composited, the MOF@plastic materials illustrated tremendous promise for interdisciplinary research in multifunctional applications, including sewage treatment, gas adsorption/separation, and the preparation of microbial fuel cells, plastic scintillators and other sensors. The review explicated the relationships between MPs/plastics and MOF materials, as well as the challenges and perspectives for their development. It can provide a deeper understanding of how MOFs remove/degrade MP/plastic particles, how MPs/plastics are recycled to prepare MOFs, and how to build multifunctional MOF@plastic composites. Overall, this analysis is anticipated to outline future prospects for turning the threats (MPs/plastics contamination) into opportunities (e.g., as ligands to prepare MOF or MOF@plastic materials for further applications).

A comprehensive review of the application of Zr-based metal-organic frameworks for electrochemical sensors and biosensors

A family of inorganic-organic hybrid crystalline materials made up of organic ligands and metal cations or clusters is known as metal-organic frameworks (MOFs). Because of their unique stability, intriguing characteristics, and structural diversity, zirconium-based MOFs (Zr-MOFs) are regarded as one of the most interesting families of MOF materials for real-world applications. Zr-MOFs that have the ligands, metal nodes, and guest molecules enclosed show distinct electrochemical reactions. They can successfully and sensitively identify a wide range of substances, which is important for both environmental preservation and human health. The rational design and synthesis of Zr-MOF electrochemical sensors and biosensors, as well as their applications in the detection of drugs, biomarkers, pesticides, food additives, hydrogen peroxide, and other materials, are the main topics of this comprehensive review. We also touch on the current issues and potential future paths for Zr-MOF electrochemical sensor research.

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.

Enzyme hybrid nanoflowers and enzyme@metal-organic frameworks composites: fascinating hybrid nanobiocatalysts

Hybrid nanomaterials have recently emerged as a new interface of nanobiocatalysis, serving as a host platform for enzyme immobilization. Enzyme immobilization in inorganic crystal nanoflowers and metal-organic frameworks (MOFs) has sparked the bulk of scientific interest due to their superior performances. Many breakthroughs have been achieved recently in the preparation of various types of enzyme@MOF and enzyme-hybrid nanoflower composites. However, it is unfortunate that there are few reviews in the literature related to enzyme@MOF and enzyme-hybrid nanoflower composites and their improved synthesis strategies and their applications in biotechnology. In this review, innovative synthetic strategies for enzyme@MOF composites and enzyme-hybrid nanoflower composites are discussed. Enzyme@MOF composites and enzyme-hybrid nanoflower composites are reviewed in terms of biotechnological applications and potential research directions. We are convinced that a fundamental study and application of enzyme@MOF composites and enzyme-hybrid nanoflower composites will be understood by the reader as a result of this work. The summary of different synthetic strategies for enzyme@MOF composites and enzyme-hybrid nanoflower composites and the improvement of their synthetic strategies will also benefit the readers and provide ideas and thoughts in the future research process.

Realizing Ultrasensitive and Accurate Point-of-Care Profiling for ATP with a Triple-Mode Strategy Based on the ATP-Induced Reassembly of a Copper Coordination Polymer Nanoflower

New strategies for accurate and reliable detection of adenosine triphosphate (ATP) with portable devices are significant for biochemical analysis, while most recently reported approaches cannot satisfy the detection accuracy and independent of large instruments simultaneously, which are unsuitable for fast, simple, and on-site ATP monitoring. Herein, a unique, convenient, and label-free point-of-care sensing strategy based on novel copper coordination polymer nanoflowers (CuCPNFs) was fabricated for multimode (UV-vis, photothermal, and RGB values) onsite ATP determination with high selectivity, sensitivity, and accuracy. The resulting CuCPNFs with a 3D hierarchical structure exhibit the ATP-triggered decomposition behavior because the competitive coordination between ATP and the copper ions of CuCPNFs can result in the formation of ATP-Cu, which reveals preeminent peroxidase mimics activity and can accelerate the oxidation of 3, 3', 5, 5'-tetramethylbenzidine (TMB) to form oxTMB. During this process, the detection system displayed not only color changes but also a strong NIR laser-driven photothermal effect. Thus, the photothermal and color signal variations are easily monitored by a portable thermometer and a smartphone. This multimode point-of-care platform can meet the requirements of onsite, without bulky equipment, accuracy, and reliability all at once, greatly enhancing its application in practice and paving a new way in ATP analysis.

Single-Mg-Atom Catalyst with a Dual Active Center as an Emerging Promising Sensing Platform

Bisphenol compounds [bisphenol A (BPA), etc.] are one class of the most important and widespread pollutants in food and environment, which pose severe endocrine disrupting effect, reproductive toxicity, immunotoxicity, and metabolic toxicity on humans and animals. Simultaneous rapid determination of BPA and its analogues (bisphenol S, bisphenol AF, etc.) with extraordinary potential resolution and sensitivity is of great significance but still extremely challenging. Herein, a series of single-atom catalysts (SACs) were synthesized by anchoring different metal atoms (Mg, Co, Ni, and Cu) on N-doped carbon materials and used as sensing materials for simultaneous detection of bisphenols with similar chemical structures. The Mg-based SAC enables the potential discrimination and simultaneous rapid detection of multiple bisphenols, showing outstanding analytical performances, outperforming all other SACs and traditional electrode materials. Our experiments and density functional theory calculations show that pyrrolic N serves as the adsorption site for the adsorption of bisphenols and the Mg atom serves as the active site for the electrocatalytic oxidation of bisphenols, which play a synergistic role as dual active centers in improving the sensing performance. The results of this work may pave the way for the rational design of SACs as advanced sensing and catalytic materials.

Advances in Bioelectrode Design for Developing Electrochemical Biosensors

The critical performance factors such as selectivity, sensitivity, operational and storage stability, and response time of electrochemical biosensors are governed mainly by the function of their key component, the bioelectrode. Suitable design and fabrication strategies of the bioelectrode interface are essential for realizing the requisite performance of the biosensors for their practical utility. A multifaceted attempt to achieve this goal is visible from the vast literature exploring effective strategies for preparing, immobilizing, and stabilizing biorecognition elements on the electrode surface and efficient transduction of biochemical signals into electrical ones (i.e., current, voltage, and impedance) through the bioelectrode interface with the aid of advanced materials and techniques. The commercial success of biosensors in modern society is also increasingly influenced by their size (and hence portability), multiplexing capability, and coupling in the interface of the wireless communication technology, which facilitates quick data transfer and linked decision-making processes in real-time in different areas such as healthcare, agriculture, food, and environmental applications. Therefore, fabrication of the bioelectrode involves careful selection and control of several parameters, including biorecognition elements, electrode materials, shape and size of the electrode, detection principles, and various fabrication strategies, including microscale and printing technologies. This review discusses recent trends in bioelectrode designs and fabrications for developing electrochemical biosensors. The discussions have been delineated into the types of biorecognition elements and their immobilization strategies, signal transduction approaches, commonly used advanced materials for electrode fabrication and techniques for fabricating the bioelectrodes, and device integration with modern electronic communication technology for developing electrochemical biosensors of commercial interest.

Buffer Effects in Zirconium-Based UiO Metal-Organic Frameworks (MOFs) That Influence Enzyme Immobilization and Catalytic Activity in Enzyme/MOF Biocatalysts

Novel biocatalysts that feature enzymes immobilized onto solid supports have recently become a major research focus in an effort to create more sustainable and greener chemistries in catalysis. Many of these novel biocatalyst systems feature enzymes immobilized onto metal-organic frameworks (MOFs), which have been shown to increase enzyme activity, stability, and recyclability in industrial processes. While the strategies used for immobilizing enzymes onto MOFs can vary, the conditions always require a buffer to maintain the functionality of the enzymes during immobilization. This report brings attention to critical buffer effects important to consider when developing enzyme/MOF biocatalysts, specifically for buffering systems containing phosphate ions. A comparative analysis of different enzyme/MOF biocatalysts featuring horseradish peroxidase and/or glucose oxidase immobilized onto the MOFs UiO-66, UiO-66-NH₂, and UiO-67 using a noncoordinate buffering system (MOPSO buffer) and a phosphate buffering system (PBS) show that phosphate ions can have an inhibitory effect. Previous studies utilizing phosphate buffers for enzyme immobilization onto MOFs have shown Fourier transform infrared (FT-IR) spectra that have been assigned stretching frequencies associated with enzymes after immobilization. Analyses and characterizations using zeta potential measurements, scanning electron microscopy, Brunauer-Emmett-Teller surface area, powder X-ray diffraction, Energy Dispersive X-ray Spectroscopy, and FT-IR show concerning differences in enzyme loading and activity based on the buffering system used during immobilization.

Metal-Organic Frameworks (MOFs)-Based Sensors for the Detection of Heavy Metals: A Review

Metal-organic-frameworks (MOFs) have emerged as promising candidates in different scientific disciplines owing to their intriguing characteristics. Their unique structural properties, including large surface area to volume ratio with multi-functionalities and ultra-high porosity, tunability, uniformity, and easy derivation and fabrication, render them effective materials for sensing applications. The detection of heavy metals in different environmental matrices using various MOF-based sensors is in practice. They include luminescent, electrochemical, electrochemiluminescent, colorimetric, and surface-enhanced Raman scattering, are of great interest. This review elaborates on selected synthetic methods for the fabrication of MOF-based sensors, modification routes for tailoring and enhancing the desired properties, basic characterization techniques, and their limitations in the detection of heavy metals. Also, it emphasizes the use of various types of MOF-based sensors alternatively for the detection of different heavy metals such as Fe(III), Cr(III), Hg(II), Cd(II), and Pb(II) in addition to a normal metal Al(III). A collection of recent references is provided for researchers interested in such applications. Results from the literature have been summarized in tables which give an easy comparison and will help to develop efficient materials.

Air-enclosed pores in graphene aerogel inhibit the adsorption of bisphenol A but accelerate the adsorption of naphthalene

Graphene hydrogel (GH) and aerogel (GA) have great application potential as highly effective adsorbents, but the accessibility of their adsorption sites have not yet been identified, restricting our understanding on the adsorption mechanisms and manufacturing. This study comparatively studied the adsorption characteristics of bisphenol A (BPA) and naphthalene (NAP) on GH and GA, focussing on the accessibility of the adsorption sites. The adsorption of BPA on GA was much lower but faster than that on GH. NAP adsorption on GA was very close to that on GH but faster than that on the latter. Considering that NAP is volatilisable, we speculate that some unwetted sites in the air-enclosed pores are available to it, but not to BPA. We applied ultrasonic and vacuum treatments to remove the air in GA pores, which was verified using a CO₂ replacement experiment. BPA adsorption was greatly enhanced but slowed, while that of NAP was not enhanced. This phenomenon suggested that some inner pores became accessible in the aqueous phase after air removal from pores. The enhanced accessibility of air-enclosed pores was verified by the increased relaxation rate of surface-bounded water on GA, based on a ¹H NMR relaxation analysis. This study highlights that the accessibility of adsorption site plays a crucial role for the adsorption properties of carbon-based aerogel. The volatile chemicals may be quickly adsorbed in the air-enclosed pores, which be useful for immobilizing volatile contaminants.

Carbon Capture Materials in Post-Combustion: Adsorption and Absorption-Based Processes

Global warming and climate changes are among the biggest modern-day environmental problems, the main factor causing these problems is the greenhouse gas effect. The increased concentration of carbon dioxide in the atmosphere resulted in capturing increased amounts of reflected sunlight, causing serious acute and chronic environmental problems. The concentration of carbon dioxide in the atmosphere reached 421 ppm in 2022 as compared to 280 in the 1800s, this increase is attributed to the increased carbon dioxide emissions from the industrial revolution. The release of carbon dioxide into the atmosphere can be minimized by practicing carbon capture utilization and storage methods. Carbon capture utilization and storage (CCUS) has four major methods, namely, pre-combustion, post-combustion, oxyfuel combustion, and direct air capture. It has been reported that applying CCUS can capture up to 95% of the produced carbon dioxide in running power plants. However, a reported cost penalty and efficiency decrease hinder the wide applicability of CCUS. Advancements in the CCSU were made in increasing the efficiency and decreasing the cost of the sorbents. In this review, we highlight the recent developments in utilizing both physical and chemical sorbents to capture carbon. This includes amine-based sorbents, blended absorbents, ionic liquids, metal-organic framework (MOF) adsorbents, zeolites, mesoporous silica materials, alkali-metal adsorbents, carbonaceous materials, and metal oxide/metal oxide-based materials. In addition, a comparison between recently proposed kinetic and thermodynamic models was also introduced. It was concluded from the published studies that amine-based sorbents are considered assuperior carbon-capturing materials, which is attributed to their high stability, multifunctionality, rapid capture, and ability to achieve large sorption capacities. However, more work must be done to reduce their cost as it can be regarded as their main drawback.

Recent Advances in Wearable Biosensors for Non-Invasive Detection of Human Lactate

Lactate, a crucial product of the anaerobic metabolism of carbohydrates in the human body, is of enormous significance in the diagnosis and treatment of diseases and scientific exercise management. The level of lactate in the bio-fluid is a crucial health indicator because it is related to diseases, such as hypoxia, metabolic disorders, renal failure, heart failure, and respiratory failure. For critically ill patients and those who need to regularly control lactate levels, it is vital to develop a non-invasive wearable sensor to detect lactate levels in matrices other than blood. Due to its high sensitivity, high selectivity, low detection limit, simplicity of use, and ability to identify target molecules in the presence of interfering chemicals, biosensing is a potential analytical approach for lactate detection that has received increasing attention. Various types of wearable lactate biosensors are reviewed in this paper, along with their preparation, key properties, and commonly used flexible substrate materials including polydimethylsiloxane (PDMS), polyethylene terephthalate (PET), paper, and textiles. Key performance indicators, including sensitivity, linear detection range, and detection limit, are also compared. The challenges for future development are also summarized, along with some recommendations for the future development of lactate biosensors.

Nanomaterial-based electrochemical enzymatic biosensors for recognizing phenolic compounds in aqueous effluents

With the rapid development of industrial society, phenolic pollutants already identified in water are severe threats to human health. Traditional detection techniques like chromatography are poor in the ability of cost-effectiveness and on-site detection. In recent years, electrochemical enzymatic biosensors have attracted increasing attention for use in the recognition of phenolic compounds, which is considered an effective strategy for the product transfer of portable analytical devices. Although electrochemical enzymatic biosensors provide a fast, accurate on-site detection technique, the difficulties of enzyme deactivation, poor stability and low sensitivity remain to be solved. Thus, effective immobilization methods of enzymes and nanomaterials with excellent properties have been extensively researched to obtain a high-sensitivity and high-stability biosensing platform. Simultaneous detection of multiple phenols may become the focus of further research. In this review, we provide an overview of recent progress toward electrochemical enzymatic biosensors for the detection of phenolic compounds, including enzyme immobilization approaches and advanced nanomaterials, especially nanocomposites with attractive properties such as good conductivity, high specific surface area, and porous structure. We will comprehensively discuss the features and mechanisms of the main enzymes adopted in the construction of different phenolic biosensors, as well as traditional methods (e.g., adsorption, covalent bonding, entrapment, encapsulation, cross-linking) of enzyme immobilization. The most effective method is based on the properties of enzymes, supports and application objective because there is no one-size-fits-all method of enzymatic immobilization. The emphasis will be given to various advanced nanomaterials, including their special nanostructures, preparation methods and performance. Finally, the main challenges in future research on electrochemical phenolic biosensors will be discussed to provide further perspectives for practical applications in dynamic and on-site monitoring. We believe this review will deliver an important inspiration for the construction of novel and high-performance electrochemical biosensors from enzyme selection to nanomaterial design for the detection of various hazardous materials. We believe this review will deliver an important inspiration on the construction of novel and high-performance electrochemical biosensors from the enzyme selection to the nanomaterial design for detections of various hazardous materials.

Design and Application of Electrochemical Sensors with Metal-Organic Frameworks as the Electrode Materials or Signal Tags

Metal-organic frameworks (MOFs) with fascinating chemical and physical properties have attracted immense interest from researchers regarding the construction of electrochemical sensors. In this work, we review the most recent advancements of MOF-based electrochemical sensors for the detection of electroactive small molecules and biological macromolecules (e.g., DNA, proteins, and enzymes). The types and functions of MOF-based nanomaterials in terms of the design of electrochemical sensors are also discussed. Furthermore, the limitations and challenges of MOF-based electrochemical sensing devices are explored. This work should be invaluable for the development of MOF-based advanced sensing platforms.

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.

Applications of metal-organic framework-based bioelectrodes

Metal-organic frameworks (MOFs) are an emerging class of porous nanomaterials that have opened new research possibilities. The inherent characteristics of MOFs such as their large surface area, high porosity, tunable pore size, stability, facile synthetic strategies and catalytic nature have made them promising materials for enormous number of applications, including fuel storage, energy conversion, separation, and gas purification. Recently, their high potential as ideal platforms for biomolecule immobilization has been discovered. MOF-enzyme-based materials have attracted the attention of researchers from all fields with the expansion of MOFs development, paving way for the fabrication of bioelectrochemical devices with unique characteristics. MOFs-based bioelectrodes have steadily gained interest, wherein MOFs can be utilized for improved biomolecule immobilization, electrolyte membranes, fuel storage, biocatalysis and biosensing. Likewise, applications of MOFs in point-of-care diagnostics, including self-powered biosensors, are exponentially increasing. This paper reviews the current trends in the fabrication of MOFs-based bioelectrodes with emphasis on their applications in biosensors and biofuel cells.

The role of MOF based nanocomposites in the detection of phenolic compounds for environmental remediation- A review

Phenolic compounds would be the emerging pollutant by 2050, because of their wide spread applicability in daily life and therefore the adoption of suitable detection methods in which identification and separation of isomers is highly desirable. Owing to the fascinating features, Metal-organic framework (MOF), a class of reticular materials holds a large surface area with tunable shape and adjustable porosity will provide strong interaction with analytes through abundant functional groups resulting in high selectivity towards electrochemical determination of phenolic isomers. Nevertheless, the sensing performance can still be further improved by building MOF network (intrinsic resistance) with functional (conducting) materials, resulting in MOF based nanocomposite. Herein, this review provides the summary of MOF based nanocomposites for electrochemical sensing of phenolic compounds developed from 2015. In this review, we discussed the demerits of pristine MOF as electrode materials, and the requirement of new class of MOF with functional materials such as nanomaterials, carbon nanotubes, graphene and MXene. The history and evolution of MOF nanocomposite-based materials are discussed and also featured the impressive physical and chemical properties. Besides this review discusses the factors influencing the conducting pathway and mass transport of MOF based nanocomposite for enhanced sensing performance of phenolic compounds with suitable mechanistic illustrations. Finally, the major challenges governing the determination of phenolic compounds and the future advancements required for the development of MOF based electrodes for various applications are highlighted.

A Status Update on the Development of Polymer and Metal-Based Graphene Electrochemical Sensors for Detection and Quantitation of Bisphenol A

The detection and quantitation of bisphenol A (BPA) in the environment and food products has been a subject of considerable interest. BPA, a diphenylmethane derivative is a well-known industrial raw material with wide range of applications. It is a well-known endocrine disruptor and acts as an estrogen mimic. BPA is an environmental health concern and its accumulation in hydro-geological cycles is a matter of serious ecological peril. This review basically assesses various chemically modified electrodes composed of diverse components that have been employed to recognize BPA in different matrices. Electrochemical sensors prepared using graphene materials in combination with metals and polymers for selective detection of BPA have been discussed extensively. The emphasis is on detection of BPA in various samples encountered in routine use such as plastic bottles, receipts, baby feed bottles, milk samples, mineralized water, tissue paper, DVDs, and others. Although research in this field is in the exploratory stage, deeper insights into fundamental studies of sensing systems, fast analysis of real samples and validation of sensors are some of the factors that need major impetus. It is expected that chemically modified electrode-based sensing systems will soon take over as a viable option for monitoring diverse pollutants.

Metal-Organic Frameworks-Based Sensors for the Detection of Toxins in Food: A Critical Mini-Review on the Applications and Mechanisms

Using scientific technologies to detect toxins in food is significant to prevent food safety problems and protect people’s health. Recently, the rise of sensors has made rapid, efficient, and safe detection of food toxins possible. One of the key factors impacting the sensor’s performance is the nanomaterials employed. Metal-organic frameworks (MOFs), with high specific surface area, tunable composition, porous structure, and flexible properties, have aroused the interest of researchers. The applications of MOFs in detecting food toxins have seen remarkable success in the past few years. In this critical mini-review, the impact of various synthesis methods on MOFs’ properties is first presented. Then, the applications and mechanisms of MOFs-based sensors in detecting various toxins are summarized and analyzed. Finally, future perspectives, potential opportunities, and challenges in this field are discussed.

Laccase bioconjugate and multi-walled carbon nanotubes-based biosensor for bisphenol A analysis

Bisphenol A (BPA) is an endocrine disruptor compound that has been detected in aquatic ecosystems. In this work, the development of an electrochemical biosensor for BPA determination based on laccase from Trametes versicolor is reported. A bioconjugate was optimized to maximize the biosensor electrocatalytic activity and stability, which for the first time involved the synergistic effect of this specific enzyme (6.8 UmL-1), chitosan (5 mgmL-1) and the ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate in an optimum 5:5:2 (v/v/v) proportion. This bioconjugate was deposited onto a screen-printed carbon electrode previously modified with multi-walled carbon nanotubes (MWCNTs). Nanostructuration with MWCNTs enlarged the electrocatalytic activity and surface area, thus improving the biosensor performance. The BPA electrochemical reaction follows an EC mechanism at the optimum pH value of 5.0. Linearity up to 12 µM, a sensitivity of (6.59 ± 0.04) × 10-2 μAμM-1 and a detection limit of 8.4 ± 0.3 nM were obtained coupled with high reproducibility (relative standard deviations lower than 6%) and stability (87% of the initial response after one month). The developed biosensor was employed to the analysis of BPA in river water displaying appropriate accuracy (94.6-97.9%) and repeatability (3.1 to 6% relative standard deviations) proving its high potential applicability for in situ environmental analysis.

Recent advancements in metal-organic frameworks composites based electrochemical (bio)sensors

Metal-organic frameworks (MOFs) are a novel class of crystalline materials which find widespread applications in the field of microporous conductors, catalysis, separation, biomedical engineering, and electrochemical sensing. With a specific emphasis on the MOF composites for electrochemical sensor applications, this review summarizes the recent construction strategies on the development of conductive MOF composites (post-synthetic modification of MOFs, in situ synthesis of functional materials@MOFs composites, and incorporating electroactive ligands). The developed composites are revealed to have excellent electrochemical sensing activity better than their pristine forms. Notably, the applicable functionalized MOFs to electrochemical sensing/biosensing of various target species are discussed. Finally, we highlight the perspectives and challenges in the field of electrochemical sensors and biosensors for potential directions of future development.

Nanostructured Carbons: towards Soft-Bioelectronics, Biosensing and Theraputic Applications

Recently, nanostructured carbon-based soft bioelectronics and biosensors have received tremendous attention due to their outstanding physical and chemical properties. The ultrahigh specific surface area, high flexibility, lightweight, high electrical conductivity, and biocompatibility of 1D and 2D nanocarbons, such as carbon nanotubes (CNT) and graphene, are advantageous for bioelectronics applications. These materials improve human life by delivering therapeutic advancements in gene, tumor, chemo, photothermal, immune, radio, and precision therapies. They are also utilized in biosensing platforms, including optical and electrochemical biosensors to detect cholesterol, glucose, pathogenic bacteria (e. g., coronavirus), and avian leucosis virus. This review summarizes the most recent advancements in bioelectronics and biosensors by exploiting the outstanding characteristics of nanocarbon materials. The synthesis and biocompatibility of nanocarbon materials are briefly discussed. In the following sections, applications of graphene and CNTs for different therapies and biosensing are elaborated. Finally, the key challenges and future perspectives of nanocarbon materials for biomedical applications are highlighted.

Understanding the endocrine disruptor and determination of bisphenol A by functional Cu-BTABB-MOF/rGO composite as facile rapid electrochemical sensor: an experimental and DFT investigation

A pioneering CuBTABB-MOF/rGO composite customized electrode is fabricated and utilized as a sensor towards identifying bisphenol A (BPA) in a phosphate buffer solution of pH 7.0. The composite is characterized by FTIR, Raman spectroscopy, XRD, SEM, EDX, HRTEM, and XPS to study its structural and morphological properties. Compared with Cu-BTABB-MOF and Cu-BTABB-MOF@GO, the Cu-BTABB-MOF@rGO modified electrode is more sensitive and selective to BPA due to a strong interaction between them. The developed Cu-BTABB-MOF@rGO modified electrode exhibits good sensitivity (6.95 × 10^-5 A mol^-1 L^-1) for BPA having a wide linear range of 0-100 μmol L^-1 with the LOD of 2.08 × 10^-5 mol L^-1, reproducibility of 4.35%, and relative standard deviation (RSD) and stability of 90% for thirty days. In addition, the developed electrocatalyst remained unoccupied from interfering substances and consequently provided an encouraging platform for swift detection of BPA in real samples such as pond water and packed water bottles. Additionally, we utilized DFT (density functional theory) to model GO and Cu-BTABB-MOF structures for detecting BPA molecules.

Ultrasensitive and Highly Selective Detection of Bisphenol a Using Core-Shell Magnetic Molecularly Imprinted Quantum Dots Electrochemiluminescent Probe

The main aim of this work was to develop a magnetic molecularly imprinted polymer (MMIP)-based quantum dots electrochemiluminescent (ECL) probe for the ultrasensitive and highly selective detection of bisphenol A (BPA). The prepared core-shell Fe₃O₄@SiO₂ exhibited superparamagnetic properties, making them easy to separate. The MIP was fabricated by the self-polymerization of dopamine on the surface of amine-terminated Fe₃O₄@SiO₂ (Fe₃O₄@SiO₂-NH₂) magnetic nanoparticles and doped with quantum dots (QDs) to form an ECL system. The ECL intensity decrease with the concentration of BPA increased, due to the BPA molecules occupied molecularly imprinted sites and blocked the strong ECL emission of QDs. The prepared ECL sensor performed satisfactorily in the detection of BPA, with a wide linear range from 10^- 4 to 10^- 9 mol L^- 1 and a low detection limit of 3.4 × 10^- 10 mol L^- 1 (S/N = 3). The recoveries of BPA achieved were in the range 96%-107% in the detection of actual water samples. The proposed ECL sensor displayed high sensitivity and stability, and may provide an approach for determining other important analytes.

Advances in Metal-organic Frameworks (MOFs) based Biosensors for Diagnosis: An Update

Metal-organic frameworks (MOFs) have significant advantages over other candidate classes of chemo-sensory materials owing to their extraordinary structural tunability and characteristics. MOF-based biosensing is a simple and convenient method for identifying various species. Biomarkers are molecular or cellular processes that link environmental exposure to a health outcome. Biomarkers are important in understanding the links between environmental chemical exposure and the development of chronic diseases, as well as in identifying disease-prone subgroups. Until now, several species, including nanoparticles (NPs) and their nanocomposites, small molecules, and unique complex systems, have been used for the chemical sensing of biomarkers. Following the overview of the field, we discussed the various fabrication methods for MOFs development in this review. We provide a thorough overview of the previous five years of progress to broaden the scope of analytes for future research. Several enzymatic and non-enzymatic sensors are offered, together with a mandatory measuring method that includes detection range and dynamic range. In addition, we reviewed the comparison of enzymatic and non-enzymatic biosensors, inventive edges, and the difficulties that need to be solved. This work might open up new possibilities for material production, sensor development, medical diagnostics, and other sensing fields.

A MOF chemosensor for highly sensitive and ultrafast detection of folic acid in biofriendly medium, paper strips and real samples

A new dansyl functionalized Zr(iv) MOF was used for ultra-fast (<5 s), highly sensitive (detection limit: 1.3 nM) and selective fluorescence sensing of folic acid in bio-fluids, real samples and paper strips.

Covalent organic framework DQTP modified pencil graphite electrode for simultaneous determination of bisphenol A and bisphenol S

The sensitivity and selectivity of electrochemical analysis are challenging due to the materials used for electrode modification as well as electrical conductivity, catalytic activity and recognition ability of the working electrode. In this work, a portable 3D-printed electrochemical electrode clamp was designed and applied in combination with the developed covalent organic framework (COF DQTP)-modified pencil graphite electrode (DQTP/PGE). The β-ketoenamine-linked COF DQTP synthesized by 1,3,5-triformylphloroglucinol (TP) and 2,6-diaminoanthraquinone (DQ) through solvothermal method is a porous crystalline with excellent conductivity and large periodic π-arrays, coupled with commercial available pencil graphite electrode to fabricate a disposable sensor for simultaneous determination of environmental endocrine disruptors bisphenol A and bisphenol S. The DQTP/PGE sensor exhibited high electrical conductivity and catalytic activity, and a good linearity was obtained in a range of 0.5-30 μM for two bisphenols with a detection limit of 0.15 μM (S/N = 3). Moreover, the sensor showed a reproducible and stable response over one month with negligible interference, and an accepted recovery with real food packaging samples.

Tetrakaidecahedron-shaped Cu four-core supramolecular as novel high-performance electrode material for lithium-ion batteries

Here, a tetrakaidecahedron-shaped Cu four-core supramolecular was designed to overcome the defects of supramoleculars for lithium-ion batteries. With multiple metal centers, conductive ligands and abundant hydrogen bonds, this novel electrode...

Metal-Organic Framework-Based Composites for the Detection and Monitoring of Pharmaceutical Compounds in Biological and Environmental Matrices

The production of synthetic drugs is considered a huge milestone in the healthcare sector, transforming the overall health, aging, and lifestyle of the general population. Due to the surge in production and consumption, pharmaceutical drugs have emerged as potential environmental pollutants that are toxic with low biodegradability. Traditional chromatographic techniques in practice are time-consuming and expensive, despite good precision. Alternatively, electroanalytical techniques are recently identified to be selective, rapid, sensitive, and easier for drug detection. Metal-organic frameworks (MOFs) are known for their intrinsic porous nature, high surface area, and diversity in structural design that provides credible drug-sensing capacities. Long-term reusability and maintaining chemo-structural integrity are major challenges that are countered by ligand-metal combinations, optimization of synthetic conditions, functionalization, and direct MOFs growth over the electrode surface. Moreover, chemical instability and lower conductivities limited the mass commercialization of MOF-based materials in the fields of biosensing, imaging, drug release, therapeutics, and clinical diagnostics. This review is dedicated to analyzing the various combinations of MOFs used for electrochemical detection of pharmaceutical drugs, comprising antibiotics, analgesics, anticancer, antituberculosis, and veterinary drugs. Furthermore, the relationship between the composition, morphology and structural properties of MOFs with their detection capabilities for each drug species is elucidated.

Tyrosinase@HKUST-1: a super stable biocatalyst efficient for catecholic product synthesis

Although metal-organic frameworks (MOFs) have been considered as promising matrices for enzyme immobilization, HKUST-1, constructed from copper acetate (CuAc2) and benzene 1,3,5-tricarboxylate (BTC), has rarely been explored for this application. In this study, mushroom tyrosinase (EC 1.14.18.1) was immobilized in the form of tyrosinase@HKUST-1 following a simple reaction procedure by mixing BTC with the enzyme prior to addition of CuAc2. The resultant biocatalyst was characterized in both structural features and catalytic properties. Upon incorporation into the HKUST-1 frameworks, the enzyme gained a prominent enhancement in stability against pH, temperature and storage: When incubated at 50 °C and pH 6.0, tyrosinase@HKUST-1 presented a half-life of 32.6 h, which is 77-fold and over tenfold higher than that of the free enzyme and its other immobilization forms, respectively; and the catalyst fully maintained its activity for at least 2 months when stored at 30 °C. The applicability of this new biocatalyst was demonstrated by employing it as catalyst for regioselective ortho-hydroxylation reactions to produce catecholic products with huge pharmacological effects, i.e., hydroxytyrosol and L-DOPA, with excellent yields and productivities. This study has thus offered a facile immobilization method to prepare a novel biocatalyst with super stability, and tyrosinase@HKUST-1 so formed from crude mushroom extract provides an efficient catalyst which can be applied to the production of catecholic products with health benefits.

Peptide-Mediated Synthesis of Zeolitic Imidazolate Framework-8: Effect of Molecular Hydrophobicity, Charge Number and Charge Location

Three amphiphilic peptides with varied molecular hydrophobicity, charge number and charge location have been designed as regulators to modulate the crystal growth of zeolitic imidazolate framework-8 (ZIF-8). All three peptides can interact with ZIF-8 to inhibit {100} facet growth and produce truncated cubic crystals. The peptide's molecular hydrophobicity plays a dominant role in defining the final morphology and size of the ZIF-8 crystals. The peptides with less charge and higher hydrophobicity can promote nuclei formation and crystal growth to give smaller ZIF-8 crystals. However, the charge located in the center of the molecular hydrophobic region has little effect on the crystal nucleation and growth due to the shielding of its charge by molecular aggregation. The study provides insights into the effect of molecular charge and hydrophobicity on ZIF-8 crystal growth and is helpful for guiding the molecular design for regulating the synthesis of metal-organic framework materials.

Quantitative detection of crystal violet using a surface-enhanced Raman scattering based on a flower-like HAp/Ag nanocomposite

Herein, we proposed a simple one-pot sol-thermal strategy to prepare a highly sensitive and reproducible SERS substrate. The silver-doped hydroxyapatite nanocomposite (HAp/Ag) could suppress the oxidation of silver nanoparticles, which endow the SERS substrate with good stability and reproducibility. Due to the strong interaction between the HAp/Ag substrate and the analytes, a stronger Raman signal generated during the process of SERS detection. In particular, the HAp/Ag substrate enabled the determination of rhodamine 6G (R6G) and crystal violet (CV), and the limits of detection (LOD) were low at 10^-6 M and 10^-5 M, respectively. In addition, the HAp/Ag substrate could be used for the quantitative analysis of CV in wastewater with a good linear relationship between 10^-2 and 10^-5 M. In this context, the HAp/Ag substrate combines the superior properties of both Ag NPs and HAp particles, providing a potential method for monitoring the environment and building a convenient SERS platform to detect pollutants in wastewater.

A new strategy for the development of efficient impedimetric tobramycin aptasensors with metallo-covalent organic frameworks (MCOFs)

Two bimetallic CoNi-based metallo-covalent organic frameworks (MCOFs) were prepared and explored as the sensitive platforms of impedimetric aptasensors for efficient detection of tobramycin (TOB). The two CoNi-MCOFs were constructed using metallophthalocyanine tetra-amine (MPc-TA, M = Co²⁺ or Ni²⁺) and 4,4'-(1,10-phen-anthroline-2,9-diyl) dibenzaldehyde (PTD) as building units and further coordinating to the secondary metal ions (Ni²⁺ or Co²⁺) by phenanthroline. Interestingly, the immobilization ability of CoPc-TA-PTD(Ni) to TOB-targeted aptamer is higher than that of NiPc-TA-PTD(Co) due to its stronger binding interactions to aptamer. As a result, the CoPc-TA-PTD(Ni)-based aptasensor shows the superior TOB detection ability, giving a low detection limit of 0.07 fg mL^-1 and satisfied sensing performances, such as high selectivity, good reproducibility, and excellent stability. Also, the aptasensor shows the acceptable applicability for detecting TOB in milk or chicken egg. This MCOFs-based sensing strategy could be extensively applied to detect other analytes by anchoring the corresponding probes.