A generic amplification strategy for electrochemical aptasensors using a non-enzymatic nanoceria tag

A novel electrochemical aptasensor based on AgPdNPs/PEI-GO and hollow nanobox-like Pt@Ni-CoHNBs for procymidone detection

Herein, an aptasensor based on a signal amplification strategy was developed for the sensitive detection of procymidone (PCM). AgPd nanoparticles/Polenimine Graphite oxide (AgPdNPs/PEI-GO) was weaned as electrode modification material to facilitate electron transport and increase the active sites on the electrode surface. Besides, Pt@Ni-Co nanoboxes (Pt@Ni-CoHNBs) were utilized to be carriers for signaling tags, after hollowing ZIF-67 and growing Pt, the resulting Pt@Ni-CoHNBs has a tremendous amounts of folds occurred on the surface, enables it to carry a larger quantity of thionine, thus amplify the detectable electrochemical signal. In the presence of PCM, the binding of PCM to the signal probe would trigger a change in electrical signal. The aptasensor was demonstrated with excellent sensitivity and a low detection limit of 0.98 pg·mL-1, along with a wide linear range of 1 μg·mL-1 to 1 pg·mL-1. Meanwhile, the specificity, stability and reproducibility of the constructed aptasensor were proved to be satisfactory.

Two decades of ceria nanoparticle research: structure, properties and emerging applications

Cerium oxide nanoparticles (CeNPs) are versatile materials with unique and unusual properties that vary depending on their surface chemistry, size, shape, coating, oxidation states, crystallinity, dopant, and structural and surface defects. This review encompasses advances made over the past twenty years in the development of CeNPs and ceria-based nanostructures, the structural determinants affecting their activity, and translation of these distinct features into applications. The two oxidation states of nanosized CeNPs (Ce3+/Ce4+) coexisting at the nanoscale level facilitate the formation of oxygen vacancies and defect states, which confer extremely high reactivity and oxygen buffering capacity and the ability to act as catalysts for oxidation and reduction reactions. However, the method of synthesis, surface functionalization, surface coating and defects are important factors in determining their properties. This review highlights key properties of CeNPs, their synthesis, interactions, and reaction pathways and provides examples of emerging applications. Due to their unique properties, CeNPs have become quintessential candidates for catalysis, chemical mechanical planarization (CMP), sensing, biomedical applications, and environmental remediation, with tremendous potential to create novel products and translational innovations in a wide range of industries. This review highlights the timely relevance and the transformative potential of these materials in addressing societal challenges and driving technological advancements across these fields.

Strategies to control mycotoxins and toxigenic fungi contamination by nano-semiconductor in food and agro-food: a review

Mycotoxins are toxic secondary metabolites generated from toxigenic fungi in the contaminated food and agro-food, which have been regarded as a serious threat to the food safety and human health. Therefore, the control of mycotoxins and toxigenic fungi contamination is of great significance and has attracted the increasing attention of researchers. As we know, nano-semiconductors have many unique properties such as large surface area, structural stability, good biocompatibility, excellent photoelectrical properties, and low cost, which have been developed and applied in many research fields. Recently, nano-semiconductors have also been promisingly applied in mitigating or controlling mycotoxins and toxigenic fungi contaminations in food and agro-food. In this review, the type, occurrence, and toxicity of main mycotoxins in food and agro-food were introduced. Then, a variety of strategies to mitigate the mycotoxin contamination based on nano-semiconductors involving mycotoxins detection, inhibition of toxigenic fungi, and mycotoxins degradation were summarized. Finally, the outlook, opportunities, and challenges have prospected in the future for the mitigation of mycotoxins and toxigenic fungi based on nano-semiconductors.

Application of Nanomaterials for Coping with Mycotoxin Contamination in Food Safety: From Detection to Control

Mycotoxins, which are toxic secondary metabolites produced by fungi, are harmful to humans. Mycotoxin-induced contamination has drawn attention worldwide. Consequently, the development of reliable and sensitive detection methods and high-efficiency control strategies for mycotoxins is important to safeguard food industry safety and public health. With the rapid development of nanotechnology, many novel nanomaterials that provide tremendous opportunities for greatly improving the detection and control performance of mycotoxins because of their unique properties have emerged. This review comprehensively summarizes recent trends in the application of nanomaterials for detecting mycotoxins (fluorescence, colorimetric, surface-enhanced Raman scattering, electrochemical, and point-of-care testing) and controlling mycotoxins (inhibition of fungal growth, mycotoxin absorption, and degradation). These detection methods possess the advantages of high sensitivity and selectivity, operational simplicity, and rapidity. With research attention on the control of mycotoxins and the gradual excavation of the properties of nanomaterials, nanomaterials are also employed for the inhibition of fungal growth, mycotoxin absorption, and mycotoxin degradation, and impressive controlling effects are obtained. This review is expected to provide the readers insight into this state-of-the-art area and a reference to design nanomaterials-based schemes for the detection and control of mycotoxins.

New analytical methods using carbon-based nanomaterials for detection of Salmonella species as a major food poisoning organism in water and soil resources

Salmonella is one of the most prevalent causing agents of food- and water-borne illnesses, posing an ongoing public health threat. These food-poisoning bacteria contaminate the resources at different stages such as production, aggregation, processing, distribution, as well as marketing. According to the high incidence of salmonellosis, effective strategies for early-stage detection are required at the highest priority. Since traditional culture-dependent methods and polymerase chain reaction are labor-intensive and time-taking, identification of early and accurate detection of Salmonella in food and water samples can prevent significant health economic burden and lessen the costs. The immense potentiality of biosensors in diagnosis, such as simplicity in operation, the ability of multiplex analysis, high sensitivity, and specificity, have driven research in the evolution of nanotechnology, innovating newer biosensors. Carbon nanomaterials enhance the detection sensitivity of biosensors while obtaining low levels of detection limits due to their possibility to immobilize huge amounts of bioreceptor units at insignificant volume. Moreover, conjugation and functionalization of carbon nanomaterials with metallic nanoparticles or organic molecules enables surface functional groups. According to these remarkable properties, carbon nanomaterials are widely exploited in the development of novel biosensors. To be specific, carbon nanomaterials such as carbon nanotubes, graphene and fullerenes function as transducers in the analyte recognition process or surface immobilizers for biomolecules. Herein the potential application of carbon nanomaterials in the development of novel Salmonella biosensors platforms is reviewed comprehensively. In addition, the current problems and critical analyses of the future perspectives of Salmonella biosensors are discussed.

A signal-enhancement fluorescent aptasensor based on the stable dual cross DNA nanostructure for simultaneous detection of OTA and AFB1

The simultaneous detection of multiple mycotoxins is of great significance for food safety and human health. Herein, a simple, convenient and accurate fluorescent aptasensor was designed based on the dual cross DNA nanostructure for the simultaneous detection of ochratoxin A (OTA) and aflatoxin B₁ (AFB₁), in which the stable dual cross DNA nanostructure provided an assay platform using the fluorescent dye-labeled aptamers as a sensing element. Owing to the higher affinity of aptamers for their target, the aptamer probes were released from the assay platform in the presence of OTA and AFB₁, resulting in an enhanced fluorescence at 570 nm and 670 nm. This "signal-on" fluorescent aptasensor assay system can effectively avoid background signals and minimize false positive. Furthermore, the designed method can realize the simultaneous detection of OTA and AFB₁ during the whole experiment. The limits of detection (LOD) were as low as 0.0058 ng/mL for OTA, ranging from 0.01 to 50 ng/mL and 0.046 ng/mL for AFB₁, ranging from 0.05 to 100 ng/mL. The proposed fluorescent aptasensor exhibits excellent performance in practical application and provides a novel approach for the simultaneous detection of multiple mycotoxins by simply changing the aptamers. A "signal-on" fluorescent aptasensor assay system based on the stable dual cross DNA nanostructure was successfully developed for simultaneous detection of OTA and AFB₁ with lower detection limits in wider linear ranges.

Carbon-Based Nanocomposite Smart Sensors for the Rapid Detection of Mycotoxins

Carbon-based nanomaterials have become the subject of intensive interest because their intriguing physical and chemical properties are different from those of their bulk counterparts, leading to novel applications in smart sensors. Mycotoxins are secondary metabolites with different structures and toxic effects produced by fungi. Mycotoxins have low molecular weights and highly diverse molecular structures, which can induce a spectrum of biological effects in humans and animals even at low concentrations. A tremendous amount of biosensor platforms based on various carbon nanocomposites have been developed for the determination of mycotoxins. Therefore, the contents of this review are based on a balanced combination of our own studies and selected research studies performed by academic groups worldwide. We first address the vital preparation methods of biorecognition unit (antibodies, aptamers, molecularly imprinted polymers)-functionalized carbon-based nanomaterials for sensing mycotoxins. Then, we summarize various types of smart sensors for the detection of mycotoxins. We expect future research on smart sensors to show a significant impact on the detection of mycotoxins in food products.

Two-Dimensional Nanostructures for Electrochemical Biosensor

Current advancements in the development of functional nanomaterials and precisely designed nanostructures have created new opportunities for the fabrication of practical biosensors for field analysis. Two-dimensional (2D) and three-dimensional (3D) nanomaterials provide unique hierarchical structures, high surface area, and layered configurations with multiple length scales and porosity, and the possibility to create functionalities for targeted recognition at their surface. Such hierarchical structures offer prospects to tune the characteristics of materials-e.g., the electronic properties, performance, and mechanical flexibility-and they provide additional functions such as structural color, organized morphological features, and the ability to recognize and respond to external stimuli. Combining these unique features of the different types of nanostructures and using them as support for bimolecular assemblies can provide biosensing platforms with targeted recognition and transduction properties, and increased robustness, sensitivity, and selectivity for detection of a variety of analytes that can positively impact many fields. Herein, we first provide an overview of the recently developed 2D nanostructures focusing on the characteristics that are most relevant for the design of practical biosensors. Then, we discuss the integration of these materials with bio-elements such as bacteriophages, antibodies, nucleic acids, enzymes, and proteins, and we provide examples of applications in the environmental, food, and clinical fields. We conclude with a discussion of the manufacturing challenges of these devices and opportunities for the future development and exploration of these nanomaterials to design field-deployable biosensors.

The role of band structure in Co- and Fe-co-doped Ba0.5Sr0.5Zr0.1Y0.1O3-δ perovskite semiconductor to design an electrochemical aptasensing platform: application in label-free detection of ochratoxin A using voltammetry

Nanocomposites can offer a platform to conjugate biorecognition features of aptamer with unique size-dependent properties of a given material, which can autoprobe the binding event based on their electroactive characteristics. Herein, we design electroactive switchable aptamer probes based on co-doped single-phase semiconducting materials employing the cyclic voltammetry method to record the current signal at each step of electrochemical characterization. To do so, we utilized a facile hydrothermal method assisted by co-precipitation method such as Co-Fe-co-doped Ba_0.5Sr_0.5Zr_0.1Y_0.1O_3-δ (CF-BSZY) and tuned the alignment of the energy band structure of the material to amplify the output of the electrochemical signal. At various steps, changes occurred in the electrochemical properties at the surface of CF-BSZY. The binding of the ssDNA with prepared materials enhances the current signal by the interaction with the target (ochratoxin A (OTA)) depressing the current signal and facilitating the construction of a novel design of electrochemical aptasensor. As a proof of concept, an electrochemical aptasensor for the detection of ochratoxin A (OTA) in rice samples has been developed. The electrochemical aptasensor provides a limit of detection (LOD) of 0.00012 μM (0.12 nM), with a linear range from 0.000247 to 0.74 μM and sound OTA recovery in real samples. The developed aptasensor is simply designed and is free of oligonucleotide labeling or decorative nanoparticle modifications. The proposed mechanism is generic in principle with the potential to translate any type of aptamer and target binding event into a detectable signal; hence, it can be largely applied to various bioreceptor recognition phenomena for subsequent applications.

Development of Two-Dimensional Nanomaterials Based Electrochemical Biosensors on Enhancing the Analysis of Food Toxicants

In recent times, food safety has become a topic of debate as the foodborne diseases triggered by chemical and biological contaminants affect human health and the food industry's profits. Though conventional analytical instrumentation-based food sensors are available, the consumers did not appreciate them because of the drawbacks of complexity, greater number of analysis steps, expensive enzymes, and lack of portability. Hence, designing easy-to-use tests for the rapid analysis of food contaminants has become essential in the food industry. Under this context, electrochemical biosensors have received attention among researchers as they bear the advantages of operational simplicity, portability, stability, easy miniaturization, and low cost. Two-dimensional (2D) nanomaterials have a larger surface area to volume compared to other dimensional nanomaterials. Hence, researchers nowadays are inclined to develop 2D nanomaterials-based electrochemical biosensors to significantly improve the sensor's sensitivity, selectivity, and reproducibility while measuring the food toxicants. In the present review, we compile the contribution of 2D nanomaterials in electrochemical biosensors to test the food toxicants and discuss the future directions in the field. Further, we describe the types of food toxicity, methodologies quantifying food analytes, how the electrochemical food sensor works, and the general biomedical properties of 2D nanomaterials.

A multi-colorimetric immunosensor for visual detection of ochratoxin A by mimetic enzyme etching of gold nanobipyramids

A multi-colorimetric immunosensor basing on the mimetic enzyme etching of gold nanobipyramids (Au NBPs) was established to detect ochratoxin A (OTA). Octahedral Cu₂O nanoparticles were successfully synthesized through a selective surface stabilization strategy, which can exhibit a peroxidase-like ability to oxidize 3,3',5,5'-tetramethylbenzidine (TMB). Au NBPs can be etched by the product, TMB²⁺, to form a significant longitudinal peak blue shift of local surface plasmon resonance. During the construction of the immunosensor, the microplate was coated with dopamine to immobilized OTA antigens, followed by the immunoreaction of OTA antibody and the Cu₂O-labled secondary antibody. A linear relationship can be found between the local surface plasmon resonance (LSPR) peak changes with the logarithm of OTA concentration in a wide range from 1 ng/L to 5 μg/L, while the detection limit was 0.47 ng/L. Meanwhile, the approximate OTA concentration can be conveniently and intuitively observed by the vivid color changes. Benefiting from the high specificity, the proposed multi-colorimetric immunoassay detection of OTA in millet samples was achieved, indicating the available potential of the immunoassay for the determination of OTA in real samples.

A review on graphene-based electrochemical sensor for mycotoxins detection

This work focuses on the study of nanomaterial-based sensors for mycotoxins detection. Due to their adverse effects on humans and animals, mycotoxins are heavily regulated, and the foodstuff and feed stocks with a high probability of being contaminated are often analyzed. In this context, the recent developments in graphene-based electrochemical sensors for mycotoxins detection were examined. The mycotoxins' toxicity implications on their detection and the development of diverse recognition elements are described considering the current challenges and limitations.

Recent advances in nanocomposite-based electrochemical aptasensors for the detection of toxins

Toxins are one of the major threatening factors to human and animal health, as well as economic growth. There is therefore an urgent demand from various communities to develop novel analytical methods for the sensitive detection of toxins in complex matrixes. Among the as-developed toxin detection strategies, nanocomposite-based aptamer sensors (termed as aptasensors) show tremendous potential for combating toxin pollution; in particular electrochemical (EC) aptasensors have received significant attention because of their unique advantages, including simplicity, rapidness, high sensitivity, low cost and suitability for field-testing. This paper reviewed the recently published approaches for the development of nanocomposite-/nanomaterial-based EC aptasensors for the detection of toxins with high assaying performance, and their potential applications in environmental monitoring, clinical diagnostics, and food safety control by summarizing the detection of different types of toxins, including fungal mycotoxins, algal toxins and bacterial enterotoxins. The effects of nanocomposite properties on the detection performance of EC aptasensors have been fully addressed for supplying readers with a comprehensive understanding of their improvement. The current technical challenges and future prospects of this subject have also been discussed.

Recent Advances in Ochratoxin A Electrochemical Biosensors: Recognition Elements, Sensitization Technologies, and Their Applications

Ochratoxin A (OTA) is a class of mycotoxin that are mainly produced by Aspergillus and Penicillium and widely found in plant origin food. OTA-contaminated foods can cause serious harm to animals and humans, while high stability of OTA makes it difficult to remove in conventional food processing. Thus, sensitive and rapid detection of OTA undoubtedly plays an important role in OTA prevention and control. In this paper, the conventional and novel methods of OTA at home and abroad are summarized and compared. The latest research progress and related applications of novel OTA electrochemical biosensors are mainly described with a new perspective. We innovatively divided the recognition element into single and combined recognition elements. Specifically, signal amplification technologies applied to the OTA electrochemical aptasensor are proposed. Furthermore, summary of the current limitations and future challenges in OTA analysis is included, which provide reference for the further research and applications.

Two-Dimensional Layered Nanomaterial-Based Electrochemical Biosensors for Detecting Microbial Toxins

Toxin detection is an important issue in numerous fields, such as agriculture/food safety, environmental monitoring, and homeland security. During the past two decades, nanotechnology has been extensively used to develop various biosensors for achieving fast, sensitive, selective and on-site analysis of toxins. In particular, the two dimensional layered (2D) nanomaterials (such as graphene and transition metal dichalcogenides (TMDs)) and their nanocomposites have been employed as label and/or biosensing transducers to construct electrochemical biosensors for cost-effective detection of toxins with high sensitivity and specificity. This is because the 2D nanomaterials have good electrical conductivity and a large surface area with plenty of active groups for conjugating 2D nanomaterials with the antibodies and/or aptamers of the targeted toxins. Herein, we summarize recent developments in the application of 2D nanomaterial-based electrochemical biosensors for detecting toxins with a particular focus on microbial toxins including bacterial toxins, fungal toxins and algal toxins. The integration of 2D nanomaterials with some existing antibody/aptamer technologies into electrochemical biosensors has led to an unprecedented impact on improving the assaying performance of microbial toxins, and has shown great promise in public health and environmental protection.

A review on recent developments in optical and electrochemical aptamer-based assays for mycotoxins using advanced nanomaterials

This review (with 163 refs) covers the recent developments of nanomaterial-based optical and electrochemical sensors for mycotoxins. The review starts with a brief discussion on occurrence, distribution, toxicity of mycotoxins and the legislations in monitoring their levels. It further outlines the research methods, various recognition matrices and the strategies involved in the development of highly sensitive and selective sensor systems. It also points out the salient features and importance of aptasensors in the detection of mycotoxins along with the different immobilization methods of aptamers. The review meticulously discusses the performance of different optical and electrochemical sensors fabricated using aptamers coupled with nanomaterials (CNT, graphene, metal nanoparticles and metal oxide nanoparticles). The review addresses the limitations in the current developments as well as the future challenges involved in the successful construction of aptasensors with the functionalized nanomaterials. Graphical abstract Recent developments in nanomaterial based aptasensors for mycotoxins are summarized. Specifically, the efficiency of the nanomaterial coupled aptasensors (such as CNT, graphene, metal nanoparticles and metal oxide nanoparticles) in optical and electrochemical methods are discussed.

Multifunctional Peroxidase-Encapsulated Nanoliposomes: Bioetching-Induced Photoelectrometric and Colorimetric Immunoassay for Broad-Spectrum Detection of Ochratoxins

In this study, a versatile dual-modal readout immunoassay platform was achieved for sensitive and broad-spectrum detection of ochratoxins based on the photocurrent response of flexible CdS/ZnO nanorod arrays/reduced graphene oxide and the localized surface plasmon resonance (LSPR) peak shift of Au nanobipyramids (Au NBPs). By using nanoliposomes as the vehicle to carry the secondary antibody and encapsulate horseradish peroxidase (HRP), the photocurrent change and the peak shift can be greatly amplified. The reaction mechanism was investigated in detail, indicating that HRP can trigger enzymatic bioetching in the presence of H₂O₂. In the photoelectrochemical detection, the oxidized HRP can etch CdS on the photoelectrode, resulting in the photocurrent change, while in the colorimetric detection, HRP can oxidize H₂O₂ to produce hydroxyl radicals that can etch Au NBPs to form multiple color changes and LSPR shifts. Compared with the common single-modal immunoassay for ochratoxins, such dual-modal immunoassay is more precise and reliable, owing to the completely independent signal conversion and transmission mechanism. Therefore, we hope that this accurate, simple, and visualized strategy may create a new avenue and provide innovative inspiration for food analysis.

Nanomaterials with enzyme-like characteristics (nanozymes): next-generation artificial enzymes (II)

An updated comprehensive review to help researchers understand nanozymes better and in turn to advance the field.

Electrochemical aptamer-based sensors for food and water analysis: A review

Global food and water safety issues have prompted the development of highly sensitive, specific, and fast analytical techniques for food and water analysis. The electrochemical aptamer-based detection platform (E-aptasensor) is one of the more promising detection techniques because of its unique combination of advantages that renders these sensors ideal for detection of a wide range of target analytes. Recent research results have further demonstrated that this technique has potential for real world analysis of food and water contaminants. This review summaries the recently developed E-aptasensors for detection of analytes related to food and water safety, including bacteria, mycotoxins, algal toxins, viruses, drugs, pesticides, and metal ions. Ten different electroanalytical techniques and one opto-electroanalytical technique commonly employed with these sensors are also described. In addition to highlighting several novel sensor designs, this review also describes the strengths, limitations, and current challenges this technology faces, and future development trend.

Chemical and Biological Sensors for Food-Quality Monitoring and Smart Packaging

The growing interest in food quality and safety requires the development of sensitive and reliable methods of analysis as well as technology for freshness preservation and food quality. This review describes the status of chemical and biological sensors for food monitoring and smart packaging. Sensing designs and their analytical features for measuring freshness markers, allergens, pathogens, adulterants and toxicants are discussed with example of applications. Their potential implementation in smart packaging could facilitate food-status monitoring, reduce food waste, extend shelf-life, and improve overall food quality. However, most sensors are still in the development stage and need significant work before implementation in real-world applications. Issues like sensitivity, selectivity, robustness, and safety of the sensing materials due to potential contact or migration in food need to be established. The current development status of these technologies, along with a discussion of the challenges and opportunities for future research, are discussed.

Progress on nanostructured electrochemical sensors and their recognition elements for detection of mycotoxins: A review

Nanomaterial-embedded sensors have been developed and applied to monitor various targets. Mycotoxins are fungal secondary metabolites that can exert carcinogenic, mutagenic, teratogenic, immunotoxic, and estrogenic effects on humans and animals. Consequently, the need for the proper regulation on foodstuff and feed materials has been recognized from times long past. This review provides an overview of recent developments in electrochemical sensors and biosensors employed for the detection of mycotoxins. Basic aspects of the toxicity of mycotoxins and the implications of their detection are comprehensively discussed. Furthermore, the development of different molecular recognition elements and nanomaterials required for the detection of mycotoxins (such as portable biosensing systems for point-of-care analysis) is described. The current capabilities, limitations, and future challenges in mycotoxin detection and analysis are also addressed.

DNA assay based on Nanoceria as Fluorescence Quenchers (NanoCeracQ DNA assay)

Functional nanomaterials with fluorescent or quenching abilities are important for the development of molecular probes for detection and studies of nucleic acids. Here, we describe a new class of molecular nanoprobes, the NanoCeracQ that uses nanoceria particles as a nanoquencher of fluorescent oligonucleotides for rapid and sensitive detection of DNA sequences and hybridization events. We show that nanoceria forms stable and reversible bionanoconjugates with oligonucleotides and can specifically recognize and detect DNA sequences in a single step. In absence of the target DNA, the nanoprobe produced minimal background fluorescence due to the high quenching efficiency of nanoceria. Competitive binding of the target induced a concentration dependent increase in the fluorescence signal due to hybridization and release of the fluorescent tag from the nanoparticle surface. The nanoprobe enabled sensitive detection of the complementary strand with a detection limit of 0.12 nM, using a single step procedure. The results show that biofunctionalized nanoceria can be used as a universal nanoquencher and nanosensing platform for fluorescent DNA detection and studies of nucleic acid interactions. This approach can find broad applications in molecular diagnostics, sensor development, gene expression profiling, imaging and forensic analysis.

Nano-Aptasensing in Mycotoxin Analysis: Recent Updates and Progress

Recent years have witnessed an overwhelming integration of nanomaterials in the fabrication of biosensors. Nanomaterials have been incorporated with the objective to achieve better analytical figures of merit in terms of limit of detection, linear range, assays stability, low production cost, etc. Nanomaterials can act as immobilization support, signal amplifier, mediator and artificial enzyme label in the construction of aptasensors. We aim in this work to review the recent progress in mycotoxin analysis. This review emphasizes on the function of the different nanomaterials in aptasensors architecture. We subsequently relate their features to the analytical performance of the given aptasensor towards mycotoxins monitoring. In the same context, a critically analysis and level of success for each nano-aptasensing design will be discussed. Finally, current challenges in nano-aptasensing design for mycotoxin analysis will be highlighted.

Functional Paper-Based Platform for Rapid Capture and Detection of CeO2 Nanoparticles

Development of systems for capture, sequestration, and tracking of nanoparticles (NPs) is becoming a significant focus in many aspects of nanotechnology and environmental research. These systems enable a broad range of applications for evaluating concentration, distribution, and effects of NPs for environmental, clinical, epidemiological, and occupational exposure studies. Herein, we describe the first example of a ligand-graft multifunctional platform for capture and detection of cerium oxide (CeO₂ or ceria) NPs. The approach involves the use of redox-active ligands containing o-dihydroxy functionality, enabling multivalent binding, surface retention, and formation of charge transfer complexes between the grafted ligand and the NPs. Using this strategy, paper-based and microarray-printed platforms with NP-capture ability involving either catechol or ascorbic acid as ligands were successfully fabricated. Surface modification was determined by infrared spectroscopy, electron microscopy, X-ray spectroscopy, and thermogravimetric analysis. Functionality was demonstrated for the rapid assessment of NPs in chemical mechanical planarization (CMP) slurries and CMP wastewaters. This novel approach can enable further development of devices and separation technologies including platforms for retention and separation of NPs and measurement tools for detection of NPs in various environments.

Thrombin aptasensor enabled by Pt nanoparticles-functionalized Co-based metal organic frameworks assisted electrochemical signal amplification

In this work, a Pt nanoparticles-functionalized Co-based metal organic frameworks (PtNPs@Co(II)MOFs@PtNPs) was synthesized and applied in electrochemical aptasensor for thrombin (TB) detection. First, the Co(II)MOFs@PtNPs were prepared via the mixed solvothermal method, which consists of inner Pt nanoparticles (PtNPs) encapsulated by aminofunctionalized Co(II)MOFs materials. Following that, additional PtNPs were adsorbed on the surface of Co(II)MOFs@PtNPs, resulting in the formation of PtNPs@Co(II)MOFs@PtNPs nanocomposite. The PtNPs@Co(II)MOFs@PtNPs nanocomposites with a large surface area were implimented as nanocarriers to immobilize a mass of TBA II for the formation of the TBA II bioconjugates that could be captured onto the electrode surface by sandwich-type format. Moreover, the PtNPs@Co(II)MOFs@PtNPs nanocomposites could directly use as redox tags for charge-generating and electron-transporting with the electron transfer from Co(II) to Co(III). Furthermore, in the presence of H₂O₂, the PtNPs@Co(II)MOF@PtNPs could effectively catalyze H₂O₂ oxidation with improvement electron transfer of redox probe, resulting in electrochemical signal amplification. Based on the above superior advantages, TB was determined in the concentration range from 0.1pM to 50nM with a detection limit of 0.33fM. Furthermore, the excellent sensitivity and selectivity can be easily established for quantitative analysis of other analytes.

Nanotechnology for Food Packaging and Food Quality Assessment

Nanotechnology has paved the way to innovative food packaging materials and analytical methods to provide the consumers with healthier food and to reduce the ecological footprint of the whole food chain. Combining antimicrobial and antifouling properties, thermal and mechanical protection, oxygen and moisture barrier, as well as to verify the actual quality of food, e.g., sensors to detect spoilage, bacterial growth, and to monitor incorrect storage conditions, or anticounterfeiting devices in food packages may extend the products shelf life and ensure higher quality of foods. Also the ecological footprint of food chain can be reduced by developing new completely recyclable and/or biodegradable packages from natural and eco-friendly resources. The contribution of nanotechnologies to these goals is reviewed in this chapter, together with a description of portable devices ("lab-on-chip," sensors, nanobalances, etc.) which can be used to assess the quality of food and an overview of regulations in force on food contact materials.

Conformational Changes of Enzymes and Aptamers Immobilized on Electrodes

Conformation constitutes a vital property of biomolecules, especially in the cases of enzymes and aptamers, and is essential in defining their molecular recognition ability. When biomolecules are immobilized on electrode surfaces, it is very important to have a control on all the possible conformational changes that may occur, either upon the recognition of their targets or by undesired alterations. Both enzymes and aptamers immobilized on electrodes are susceptible to conformational changes as a response to the nature of the charge of the surface and of the surrounding environment (pH, temperature, ionic strength, etc.). The main goal of this review is to analyze how the conformational changes of enzymes and aptamers immobilized on electrode surfaces have been treated in reports on biosensors and biofuel cells. This topic was selected due to insufficient information found on the actual conformational changes involved in the function of these bioelectrochemical devices despite its importance.

Biomolecular detection at ssDNA-conjugated nanoparticles by nano-impact electrochemistry

We describe the use of ssDNA functionalized silver nanoparticle (AgNP) probes for quantitative investigation of biorecognition and real time detection of biomolecular targets using nano-impact electrochemistry. The method is based on measurements of the individual collision events between ssDNA aptamer-functionalized AgNPs and a carbon fiber miroelectrode (CFME). Specific binding events of target analyte induced collision frequency changes enabling ultrasensitive detection of the aptamer target in a single step. These changes are assigned to the surface coverage of the NP by the ssDNA aptamers and subsequent conformational changes of the aptamer probe which affect the electron transfer between the NP and the electrode surface. The method enables sensitive and selective detection of ochratoxin A (OTA), chosen here as a model target, with a limit of detection of 0.05nM and a relative standard deviation of 4.9%. The study provides a means of characterizing bioconjugation of AgNPs with aptamers and assessing biomolecular recognition events with high sensitivity and without the use of exogenous reagents or enzyme amplification steps. This methodology can be broadly applicable to other bioconjugated systems, biosensing and related bioanalytical applications.

Recent Progresses in Nanobiosensing for Food Safety Analysis

With increasing adulteration, food safety analysis has become an important research field. Nanomaterials-based biosensing holds great potential in designing highly sensitive and selective detection strategies necessary for food safety analysis. This review summarizes various function types of nanomaterials, the methods of functionalization of nanomaterials, and recent (2014-present) progress in the design and development of nanobiosensing for the detection of food contaminants including pathogens, toxins, pesticides, antibiotics, metal contaminants, and other analytes, which are sub-classified according to various recognition methods of each analyte. The existing shortcomings and future perspectives of the rapidly growing field of nanobiosensing addressing food safety issues are also discussed briefly.

A single use electrochemical sensor based on biomimetic nanoceria for the detection of wine antioxidants

We report the development and characterization of a disposable single use electrochemical sensor based on the oxidase-like activity of nanoceria particles for the detection of phenolic antioxidants. The use of nanoceria in the sensor design enables oxidation of phenolic compounds, particularly those with ortho-dihydroxybenzene functionality, to their corresponding quinones at the surface of a screen printed carbon electrode. Detection is carried out by electrochemical reduction of the resulting quinone at a low applied potential of -0.1V vs the Ag/AgCl electrode. The sensor was optimized and characterized with respect to particle loading, applied potential, response time, detection limit, linear concentration range and sensitivity. The method enabled rapid detection of common phenolic antioxidants including caffeic acid, gallic acid and quercetin in the µM concentration range, and demonstrated good functionality for the analysis of antioxidant content in several wine samples. The intrinsic oxidase-like activity of nanoceria shows promise as a robust tool for sensitive and cost effective analysis of antioxidants using electrochemical detection.

Reactivity of nanoceria particles exposed to biologically relevant catechol-containing molecules

The interaction of nanoceria with catecholic molecules was investigated to obtain mechanistic information of the surface reactivity of these particles, and develop predictive models of their behavior and potential effects in complex environments.

Portable Nanoparticle-Based Sensors for Food Safety Assessment

The use of nanotechnology-derived products in the development of sensors and analytical measurement methodologies has increased significantly over the past decade. Nano-based sensing approaches include the use of nanoparticles (NPs) and nanostructures to enhance sensitivity and selectivity, design new detection schemes, improve sample preparation and increase portability. This review summarizes recent advancements in the design and development of NP-based sensors for assessing food safety. The most common types of NPs used to fabricate sensors for detection of food contaminants are discussed. Selected examples of NP-based detection schemes with colorimetric and electrochemical detection are provided with focus on sensors for the detection of chemical and biological contaminants including pesticides, heavy metals, bacterial pathogens and natural toxins. Current trends in the development of low-cost portable NP-based technology for rapid assessment of food safety as well as challenges for practical implementation and future research directions are discussed.

Recent Advances for the Detection of Ochratoxin A

Ochratoxin A (OTA) is one of the mycotoxins secreted by Aspersillus and Penicillium that can easily colonize various grains like coffee, peanut, rice, and maize. Since OTA is a chemically stable compound that can endure the physicochemical conditions of modern food processing, additional research efforts have been devoted to develop sensitive and cost-effective surveillance solutions. Although traditional chromatographic and immunoassays appear to be mature enough to attain sensitivity up to the regulation levels, alternative detection schemes are still being enthusiastically pursued in an attempt to meet the requirements of rapid and cost-effective detections. Herein, this review presents recent progresses in OTA detections with minimal instrumental usage, which have been facilitated by the development of OTA aptamers and by the innovations in functional nanomaterials. In addition to the introduction of aptamer-based OTA detection techniques, OTA-specific detection principles are also presented, which exclusively take advantage of the unique chemical structure and related physicochemical characteristics.