Metal-organic framework-based sensors for the detection of toxins and foodborne pathogens

Detection of Foodborne Pathogens in Contaminated Food Using Nanomaterial-Based Electrochemical Biosensors

Foodborne pathogens are a grave concern for the for food, medical, environmental, and economic sectors. Their ease of transmission and resistance to treatments, such as antimicrobial agents, make them an important challenge. Food tainted with these pathogens is swiftly rejected, and if ingested, can result in severe illnesses and even fatalities. This review provides and overview of the current status of various pathogens and their metabolites transmitted through food. Despite a plethora of studies on treatments to eradicate and inhibit these pathogens, their indiscriminate use can compromise the sensory properties of food and lead to contamination. Therefore, the study of detection methods such as electrochemical biosensors has been proposed, which are devices with advantages such as simplicity, fast response, and sensitivity. However, these biosensors may also present some limitations. In this regard, it has been reported that nanomaterials with high conductivity, surface-to-volume ratio, and robustness have been observed to improve the detection of foodborne pathogens or their metabolites. Therefore, in this work, we analyze the detection of pathogens transmitted through food and their metabolites using electrochemical biosensors based on nanomaterials.

Emerging Biomimetic Sensor Technologies for the Detection of Pathogenic Bacteria: A Commercial Viability Study

Ensuring a rapid and accurate identification of harmful bacteria is crucial in various fields including environmental monitoring, food safety, and clinical diagnostics. Conventional detection methods often suffer from limitations such as long analysis time, complexity, and the need for qualified personnel. Therefore, a lot of research effort is devoted to developing technologies with the potential to revolutionize the detection of pathogenic bacteria by offering rapid, sensitive, and user-friendly platforms for point-of-care analysis. In this light, biosensors have gained significant commercial attention in recent years due to their simplicity, portability, and rapid analysis capabilities. The purpose of this review is to identify a trend by analyzing which biosensor technologies have become commercially successful in the field of bacteria detection. Moreover, we highlight the characteristics that a biosensor must possess to finally arrive in the market and therefore in the hands of the end-user, and we present critical examples of the market applications of various technologies. The aim is to investigate the reason why certain technologies have achieved commercial success and extrapolate these trends to the future economic viability of a new subfield in the world of biosensing: the development of biomimetic sensor platforms. Therefore, an overview of recent advances in the field of biomimetic bacteria detection will be presented, after which the challenges that need to be addressed in the coming years to improve market penetration will be critically evaluated. We will zoom into the current shortcomings of biomimetic sensors based on imprinting technology and aptamers and try to come up with a recommendation for further development based on the trends observed from previous commercial success stories in biosensing.

Porphyrin Metal-organic Framework Sensors for Chemical and Biological Sensing

Porphyrins and porphyrin derivatives have been intensively explored for a number of applications such as sensing, catalysis, adsorption, and photocatalysis due to their outstanding photophysical properties. Their usage in sensing applications, however, is limited by intrinsic defects such as physiological instability and self-quenching. To reduce self-quenching susceptibility, researchers have developed porphyrin metal-organic frameworks (MOFs). Metal-organic frameworks (MOFs), a unique type of hybrid porous coordination polymers comprised of metal ions linked by organic linkers, are gaining popularity. Porphyrin molecules can be integrated into MOFs or employed as organic linkers in the production of MOFs. Porphyrin-based MOFs are a separate branch of the huge MOF family that combines the distinguishing qualities of porphyrins (e.g., fluorescent nature) and MOFs (e.g., high surface area, high porosity) to enable sensing applications with higher sensitivity, specificity, and extended target range. The key synthesis techniques for porphyrin-based MOFs, such as porphyrin@MOFs, porphyrinic MOFs, and composite porphyrinic MOFs, are outlined in this review article. This review article focuses on current advances and breakthroughs in the field of porphyrin-based MOFs for detecting a variety of targets (for example, metal ions, anions, explosives, biomolecules, pH, and toxins). Finally, the issues and potential future uses of this class of emerging materials for sensing applications are reviewed.

Role of Metal-Organic Frameworks (MOFs) in treating and diagnosing microbial infections

This review article highlights the innovative role of metal-organic frameworks (MOFs) in addressing global healthcare challenges related to microbial infections. MOFs, comprised of metal nodes and organic ligands, offer unique properties that can be applied in the treatment and diagnosis of these infections. Traditional methods, such as antibiotics and conventional diagnostics, face issues such as antibiotic resistance and diagnostic limitations. MOFs, with their highly porous and customizable structure, can encapsulate and deliver therapeutic or diagnostic molecules precisely. Their large surface area and customizable pore structures allow for sensitive detection and selective recognition of microbial pathogens. They also show potential in delivering therapeutic agents to infection sites, enabling controlled release and possible synergistic effects. However, challenges like optimizing synthesis techniques, enhancing stability, and developing targeted delivery systems remain. Regulatory and safety considerations for clinical translation also need to be addressed. This review not only explores the potential of MOFs in treating and diagnosing microbial infections but also emphasizes their unique approach and discusses existing challenges and future directions.

Nanomaterial-based biosensors for the detection of foodborne bacteria: a review

Ensuring food safety is a critical concern for the development and well-being of humanity, as foodborne illnesses caused by foodborne bacteria have increasingly become a major public health concern worldwide. Traditional food safety monitoring systems are expensive and time-consuming, relying heavily on specialized equipment and operations. Therefore, there is an urgent need to develop low-cost, user-friendly and highly sensitive biosensors for detecting foodborne bacteria. In recent years, the combination of nanomaterials with optical biosensors has provided a prospective future platform for the detection of foodborne bacteria. By harnessing the unique properties of nanomaterials, such as their high surface area-to-volume ratio and exceptional sensitivity, in tandem with the precision of optical biosensing techniques, a new prospect has opened up for the rapid and accurate identification of potential bacterial contaminants in food. This review focuses on recent advances and new trends of nanomaterial-based biosensors for the detection of foodborne pathogens, which mainly include noble metal nanoparticles (NMPs), metal organic frameworks (MOFs), graphene nanomaterials, quantum dot (QD) nanomaterials, upconversion fluorescent nanomaterials (UCNPs) and carbon dots (CDs). Additionally, we summarized the research progress of color indicators, nanozymes, natural enzyme vectors and fluorescent dye biosensors, focusing on the advantages and disadvantages of nanomaterial-based biosensors and their development prospects. This review provides an outlook on future technological directions and potential applications to help identify the most promising areas of development in this field.

Two-Dimensional Cu-Porphyrin Metal-Organic Framework Nanosheet-Supported Flaky TiO2 as an Efficient Visible-Light-Driven Photocatalyst for Dye Degradation and Cr(VI) Reduction

A series of 2D M(Cu, Zn, Co, and Mn)-TCPP MOFs/TiO2 binary nanocomposites (TCPP = tetrakis(4-carboxyphenyl)porphyrin) were constructed by solvothermal in situ loading of flaky TiO2 on the surface of 2D metal-organic frameworks (MOFs). The influence of different coordination metals on the catalytic activity was studied, and it was found that the 2D Cu-TCPP MOFs/TiO2 nanocomposite exhibited the best photo-Fenton performance. The superior property can be attributed to the high absorption coefficient and ultrathin two-dimensional structure of the 2D Cu-TCPP MOFs nanosheets. Meanwhile, the 2D Cu-TCPP MOFs/TiO2 II heterostructure can effectively promote the separation and transfer of photoformed carriers. Moreover, under visible irradiation, the optimized 2D Cu-TCPP MOFs/TiO2 composite can convert 99.9% of Cr(VI) to Cr(III) within 60 min with methanol as the hole scavenger at pH 3.14. Also, the photocatalytic performance of 2D Cu-TCPP MOFs/TiO2 was maintained after five reaction cycles. Furthermore, the proposed visible-light-driven photocatalysis mechanism of the 2D Cu-MOFs/TiO2 composite was reasonably derived according to experimental results. This study demonstrates the potential of building efficient TiO2-based visible light photocatalysts with 2D metal-porphyrin MOFs.

Aptamer-modified metal organic frameworks for measurement of food contaminants: a review

The measurement of food contaminants faces a great challenge owing to the increasing demand for safe food, increasing consumption of fast food, and rapidly changing patterns of human consumption. As different types of contaminants in food products can pose different levels of threat to human health, it is desirable to develop specific and rapid methods for their identification and quantification. During the past few years, metal-organic framework (MOF)-based materials have been extensively explored in the development of food safety sensors. MOFs are porous crystalline materials with tunable composition, dynamic porosity, and facile surface functionalization. The construction of high-performance biosensors for a range of applications (e.g., food safety, environmental monitoring, and biochemical diagnostics) can thus be promoted through the synergistic combination of MOFs with aptamers. Accordingly, this review article delineates recent innovations achieved for the aptamer-functionalized MOFs toward the detection of food contaminants. First, we describe the basic concepts involved in the detection of food contaminants in terms of the advantages and disadvantages of the commonly used analytical methods (e.g., DNA-based methods (PCR/real-time PCR/multiplex PCR/digital PCR) and protein-based methods (enzyme-linked immunosorbent assay/immunochromatography assay/immunosensor/mass spectrometry). Afterward, the progress in aptamer-functionalized MOF biosensors is discussed with respect to the sensing mechanisms (e.g., the role of MOFs as signal probes and carriers for loading signal probes) along with their performance evaluation (e.g., in terms of sensitivity). We finally discuss challenges and opportunities associated with the development of aptamer-functionalized MOFs for the measurement of food contaminants.

Metal-organic frameworks for food contaminant adsorption and detection

Metal-organic framework materials (MOFs) have been widely used in food contamination adsorption and detection due to their large specific surface area, specific pore structure and flexible post-modification. MOFs with specific pore size can be targeted for selective adsorption of some contaminants and can be used as pretreatment and pre-concentration steps to purify samples and enrich target analytes for food contamination detection to improve the detection efficiency. In addition, MOFs, as a new functional material, play an important role in developing new rapid detection methods that are simple, portable, inexpensive and with high sensitivity and accuracy. The aim of this paper is to summarize the latest and insightful research results on MOFs for the adsorption and detection of food contaminants. By summarizing Zn-based, Cu-based and Zr-based MOFs with low cost, easily available raw materials and convenient synthesis conditions, we describe their principles and discuss their applications in chemical and biological contaminant adsorption and sensing detection in terms of stability, adsorption capacity and sensitivity. Finally, we present the limitations and challenges of MOFs in food detection, hoping to provide some ideas for future development.

Two-Dimensional and Three-Dimensional Coordination Polymers Based on Ln(III) and 2,5-Diiodoterephthalates: Structures and Luminescent Behavior

Five new coordination polymers based on Ln3+ and 2,5-diiodoterephthalates (2,5-I-bdc)— {[La2(2,5-I-bdc)3(DMF)4]}·2DMF (1) and {[Ln2(2,5-I-bdc)3(DMF)4]} (Ln = La (2), Nd (3), Sm (4) and Eu (5))—were prepared and characterized by single crystal and powder X-ray diffractometry. Luminescent behavior was examined (the highest quantum yield is 4.5%); thermal stability was examined using thermogravimetric analysis.

Design and Development of Magnetic Iron Core Gold Nanoparticle-Based Fluorescent Multiplex Assay to Detect Salmonella

Salmonella is a bacterial pathogen which is one of the leading causes of severe illnesses in humans. The current study involved the design and development of two methods, respectively using iron oxide nanoparticle (IONP) and iron core gold nanoparticle (ICGNP), conjugated with the Salmonella antibody and the fluorophore, 4-Methylumbelliferyl Caprylate (4-MUCAP), used as an indicator, for its selective and sensitive detection in contaminated food products. Twenty double-blind beverage samples, spiked with Salmonella enteritidis, Staphylococcus aureus, and Escherichia coli, were prepared in sterile Eppendorf^® tubes at room temperature. The gold layer and spikes of ICGNPs increased the surface areas. The ratio of the surface area is 0.76 (IONPs/ICGNPs). The comparative sensitivity and specificity of the IONP-based and the ICGNP-based methods to detect Salmonella were determined. The ICGNP method shows the limit of detection is 32 Salmonella per mL. The ICGNPs had an 83.3% sensitivity and a 92.9% specificity value for the presence and detection of Salmonella. The IONP method resulted in a limit of detection of 150 Salmonella per mL, and a 66.7% sensitivity and 83.3% specificity for the presence and detection of Salmonella. The higher surface area of ICGNPs increases the efficiency of detection. The monitoring of Salmonella can thus be achieved by a rapid magnetic fluorescent assay using a smartphone for image capture and analyze, providing quantitative results. The findings from the present study would help to detect Salmonella rapidly in water. It can improve the microbial quality of water and food safety due to the presence of Salmonella in the water environment.

Recent Progress in Aptamer-Functionalized Metal-Organic Frameworks-Based Optical and Electrochemical Sensors for Detection of Mycotoxins

Mycotoxin contamination in foodstuffs and agricultural products has posed a serious hazard to human health and raised international concern. The progress of cost-effective, facile, rapid and reliable analytical tools for mycotoxin determination is in urgent need. In this regard, the potential utility of metal-organic frameworks (MOFs) as a class of crystalline porous materials has sparked immense attention due to their large specific surface area, adjustable pore size, nanoscale framework structure and good chemical stability. The amalgamation of MOFs with high-affinity aptamers has resulted in the progress of advanced aptasensing methods for clinical and food/water safety diagnosis. Aptamers have many advantages over classical approaches as exceptional molecular recognition constituents for versatile bioassays tools. The excellent sensitivity and selectivity of the MOF-aptamer biocomposite nominate them as efficient lab-on-chip tools for portable, label-free, cost-effective and real-time screening of mycotoxins. Current breakthroughs in the concept, progress and biosensing applications of aptamer functionalized MOFs-derived electrochemical and optical sensors for mycotoxins have been discussed in this study. We first highlighted an overview part, which provides some insights into the functionalization mechanisms of MOFs with aptamers, offering a foundation to create MOFs-based aptasensors. Then, we discuss various strategies to design high-performance MOFs-based aptamer scaffolds, which serve as either signal nanoprobe carriers or signal nanoprobes and their applications. We perceived that applications of optical aptamers are in their infancy in comparison with electrochemical MOFs-derived aptasensors. Finally, current challenges and prospective trends of MOFs-aptamer sensors are discussed.

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.

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.

Advanced Metal–Organic Frameworks-Based Catalysts in Electrochemical Sensors

Developing efficient catalysts is vital for the application of electrochemical sensors. Metal–organic frameworks (MOFs), with high porosity, large specific surface area, good conductivity, and biocompatibility, have been widely used in catalysis, adsorption, separation, and energy storage applications. In this invited review, the recent advances of a novel MOF-based catalysts in electrochemical sensors are summarized. Based on the structure–activity–performance relationship of MOF-based catalysts, their mechanism as electrochemical sensor, including metal cations, synthetic ligands, and structure, are introduced. Then, the MOF-based composites are successively divided into metal-based, carbon-based, and other MOF-based composites. Furthermore, their application in environmental monitoring, food safety control, and clinical diagnosis is discussed. The perspective and challenges for advanced MOF-based composites are proposed at the end of this contribution.

Zn(II) and Co(II) 3D Coordination Polymers Based on 2-Iodoterephtalic Acid and 1,2-bis(4-pyridyl)ethane: Structures and Sorption Properties

Metal-organic frameworks [M₂(2-I-bdc)₂bpe] (M = Zn(II) (1), Co(II) (2), 2-I-bdc = 2-iodoterephtalic acid, and bpe = 1,2-bis(4-pyridyl)ethane) were prepared and characterized by X-ray diffractometry. Both compounds retain their 3D structure after the removal of guest DMF molecules. Selectivity of sorption of different organic substrates from the gas phase was investigated for both complexes.