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Electrochemical biosensors: enabling rapid and cost-effective point-of-care (POC) diagnostics.

A 3D printed hydrogel-based adsorbent provides an easy, eco-friendly, and cost-effective way to remove heavy metal ions from aqueous environments.

Sensitive detection of redox active analytes utilising its fluorescent nature requires a direct non-complicated approach to amplify its emission intensity. In this regard, we investigated nanoscale cerium oxide for its unique nanosized structure, surface reactivity and redox activity coupled with surface complexation. Variations in either oxidation state or the surface-terminated oxygen of the cerium oxide nanoparticales provide gaps for the adsorption of redox functionalities. It enables ceria particles to concentrate the analyte molecules on their surface promoting fluorescence signal amplification. As a proof of concept, we integrated surface complexation feature of nanoceria towards improved fluorescent response and successively implemented them for ultra-sensitive identification of a redox active Ochratoxin A (OTA) at specific wavelength range. Results obtained indicate that higher amplification efficacy of nanoparticles is due to its higher electron mobility along with good absorbability. Different identification techniques including XRD SEM, UV–Vis, EDX, FTIR, photoluminescence, RAMAN spectroscopy and finally fluorescence assays were performed to examine morphology and nano-surface chemistry along with signal amplified strategy of the developed nano-probe. Various experimental factors including incubation time, pH and concentrations of OTA and ceria particles were also optimised. Under optimised environment, the limit of detection was as smaller as 0.1 ng mL−1 with 0.5–100 ng mL−1of linear range. Thus, we proposed a highly sensitive and selective fluorescent nanoprobe for analytical applications based on surface complexation affinity and fluorescence signal amplification ability of nanoceria.

Food freshness monitoring, which can reflect the quality of the product at the time of use, remains a great challenge for consumers and the food industry. Herein, we report the development of a cost-effective enzyme-based paper biosensor, which can monitor fish freshness and predict spoilage. The biosensor measures the release of hypoxanthine (HX), an indicator of meat and fish degradation, using the enzymatic conversion of HX by xanthine oxidase (XOD). We demonstrate that the entrapment of XOD and an organic dye, nitro blue tetrazolium chloride (NBT), within a sol-gel biohybrid enables their stabilization on paper and promotes the enzymatic reaction with further retention of the reaction products within the cellulosic network . Linearity in the micromolar concentration range with a detection limit of 3.7 μM for HX is obtained. The biosensor has high selectivity toward HX and is manufactured in few steps from inexpensive widely available materials. The applicability of the biosensor is demonstrated by following fish degradation over time and measuring HX concentrations ranging from 117 (±9) to 198 (±5) μM within 24 h of degradation, at levels that are comparable with those measured by a commercial enzymatic kit for HX detection. As compared to the commercial kit, our biosensors are more cost-effective, do not require addition of exogenous reagents and are portable, having all of the reagents needed for analysis embedded within the sensing platform. This proof-of-concept work demonstrates that the paper-based HX biosensor has potential as a robust reagentless device for real-time monitoring of food freshness and for other applications in which HX plays an important role.

Phosphate removal has become a critical need to mitigate the negative effect of water eutrophication, which is responsible for the overgrowth of toxic algal blooms and the significant ecological harm generated to aquatic ecosystems. However, some of the currently available adsorbents have low removal capacity and function optimally at specific pH ranges. Here, we present an example of a cerium-based metal-organic framework (MOF) as a high-capacity sorbent for phosphate removal from eutrophic waters. Specifically, a Ce(IV)-based UiO-66 analogue, Ce 1,4-benzenedicarboxylate (Ce-BDC), was selected due to its water stability, high surface area, microporous structure, and the high binding affinity of phosphate with its open metal sites. Mechanistic studies supported by density functional theory (DFT) calculations indicate the formation of a Ce-O-P bond through ion exchange between the terminal (nonbridging) hydroxyl groups at the missing linker sites and the phosphate adducts. Experimental results demonstrate that Ce-BDC is highly selective for phosphates over other common anions (Cl-, Br-, I-, NO3-, HCO3-, SO42-) and stable in a broad pH range of (2-12), covering the relevant range for the treatment of contaminants in aquatic systems. The sorbent shows a fast removal rate, capturing significant amounts of phosphate within 4 min with a maximum adsorption capacity of 179 mg·g-1, outperforming other porous materials. These results show a remarkable adsorption capacity and fast kinetics compared with the current state-of-the-art crystalline porous materials. This study may advance the design of new microporous materials with high adsorption capabilities, good stability, and make a significant contribution to the development of future generation technology to mitigate the negative effects of water eutrophication.

Exposure to excessive ultraviolet (UV) radiation can have detrimental effects on human health. Inexpensive easy-to-use sensors for monitoring UV radiation can allow broad-scale assessment of UV exposure, but their implementation requires technology that enables rapid and affordable manufacturing of these sensors on a large scale. Herein, we report a novel three-dimensional (3D) printing procedure and printable ink composition that produce robust, flexible, and wearable UV sensors. To fabricate the sensors, a color-changing hydrogel ink was first developed from which standalone constructs were 3D printed. The ink contains alginate, gelatin, photoactive titanium dioxide nanoparticles, and dyes (methyl orange, methylene blue, and malachite green) in which the nanoparticles are used to initiate photocatalytic degradation of dyes, leading to discoloration of the dye. The sensors resemble a color-changing tattoo that loses color upon exposure to UV. The viscosity and ink composition were optimized to achieve printability and tune the mechanical properties (e.g., modulus, hardness) of the sensors. The optimized procedure enabled the one-step fabrication of mechanically stable sensors that can effectively measure outdoor sun exposure by quantifying the decrease in color, visible to the naked eye. Apart from being used as wearable sensors, these sensors have the potential to be used along with UV-based workspace sterilizing devices to ensure that surfaces have been efficiently exposed to UV. The sensors are inexpensive, stable, extremely robust, biodegradable, and easy to use. The tunability, biocompatibility, and printability of the ink offer excellent potential for developing advanced 3D printing methods that, in addition to UV sensors, can be applied more broadly to fabricate other sensing technologies for a variety of other applications.

Nanoelectrochemistry allows for the investigation of the interaction of per- and polyfluoroalkyl substances (PFASs) with silver nanoparticles (AgNPs) and the elucidation of the binding behaviour of PFASs to nanoscale surfaces with high sensitivity. Mechanistic studies supported by single particle collision electrochemistry (SPCE), spectroscopic and density functional theory (DFT) calculations indicate the capability of polyfluorooctane sulfonic acid (PFOS), a representative PFAS, to selectively bind and induce aggregation of AgNPs. Single-particle measurements provide identification of the "discrete" AgNPs agglomeration (e.g. 2-3 NPs) formed through the inter-particles F-F interactions and the selective replacement of the citrate stabilizer by the sulfonate of the PFOS. Such interactions are characteristic only for long chain PFAS (-SOsub3/subsup-/sup) providing a means to selectively identify these substances down to ppt levels. Measuring and understanding the interactions of PFAS at nanoscale surfaces are crucial for designing ultrasensitive methods for detection and for modelling and predicting their interaction in the environment.

Ceria nanoparticles (CeNPs) are promising enzyme mimetic catalysts due to their mixed oxidation states Ce3+/Ce4+ accompanied by the presence of oxygen vacancies. While their properties have been wi...

The rapid advancement of nanotechnology has provided opportunities for the development of new sensing and food packaging solutions, addressing long-standing challenges in the food sector to extend shelf-life, reduce waste, assess safety and improve the quality of food. Nanomaterials can be used to reinforce mechanical strength, enhance gas barrier properties, increase water repellence, and provide antimicrobial and scavenging activity to food packaging. They can be incorporated in chemical and biological sensors enabling the design of rapid and sensitive devices to assess freshness, and detect allergens, toxins or pathogenic contaminants. This review summarizes recent studies on the use of nanomaterials in the development of: (1) (bio)sensing technologies for detection of nutritional and non-nutritional components, antioxidants, adulterants and toxicants, (2) methods to improve the barrier and mechanical properties of food packaging, and (3) active functional packaging. The environmental, health and safety implications of nanomaterials in the food sector, along with an overview of regulation and consumer perception is also provided.

We describe a rapid and sensitive electrochemical approach to evaluate the interaction of arsenite (As3+) with magnetic Fe3O4 nanoparticles (MNPs) by single particle collision electrochemistry (SPCE). The method is based on direct measurements of the (As3+) adsorbed on single MNPs, quantified via the oxidation of As3+ to As5+ at 0.4 V vs. Ag/AgCl, as the As-MNPs collide with a gold microelectrode (AuME). Measurement of the intensity of current spikes and the charge passed per impact spike provides a measure of As3+ content adsorbed per MNP. The total calculated charge passed at AuME was monitored over 400 s collision time and the As3+ adsorption was quantified at different pH and environmental conditions. The charge increased significantly for MNPs exposed to a natural organic material, humic acid (HA), at concentrations of up to 5 ppm, and when the pH of the solution was between 6 and 8, indicating enhanced adsorption. The concentration of As3+ (0.013–0.036 fM As/MNP) was found to correlate well with the initial concentration of As3+ in solution (0.001–10 μM), suggesting that the method can also be used as an analytical tool to determine As contamination in environmental samples. The results were confirmed with spectroscopic techniques and demonstrate As3+ adsorption. Overall, this study demonstrates the capability of SPCE to fundamentally probe the surface properties of magnetite with high resolution and elemental specificity allowing a direct ultrasensitive assessment of the As3+ loading on individual MNPs. This approach could be used as a simple cost effective and fast screening tool to evaluate heavy metal ion adsorption on nanomaterial sorbents for environmental monitoring and remediation applications.

While phosphorus (P) is an essential nonrenewable resource and a key nutrient for agricultural production, its excessive accumulation in the environment can cause overgrowth of water plants and alg...

Copper (Cu2+)-containing pesticides are commonly used in agriculture to control fungal and bacterial diseases, but the release of large quantities of Cu2+ in water and soil can lead to harmful long...

The direct monitoring of biofilm formation enables valuable insights into the industrial processes, microbiology, and biomedical applications. Therefore, in the present study, nano-structured bioelectrochemical platforms were designed for sensing the formation of biofilm of P. aeruginosa along with monitoring its electrochemical/morphological changes under different stresses. Through the assay optimizations, the performances of different electrode modifiers such as reduced graphene oxide (rGO) nanosheets, hyperbranched chitosan nanoparticles (HBCs NPs), and rGO-HBCs nano-composite were tested to assess the influence of the electrode materials on biofilm progression. As a need for the anodic respiration, the bioelectrochemical responses of the adhered bacterial cells changed from a non-electrochemically active (planktonic state) to an electrochemically active (biofilm matrix) state. Our results demonstrated that electrode modifications with conductive nanostructured elements is highly sensitive and enable direct assay for the biofilm formation without any preachments. Consequently, the morphological changes in bacterial cell wall, upon switching from the planktonic state to the biofilm matrix were imaged using scanning electron microscopy (SEM), and the changes in cell wall chemical composition were monitored by the Energy Dispersive X-ray analysis (EDX). Thus, the designed microbial electrochemical system (MES) was successfully used to monitor changes in the biofilm matrix under different stresses through direct measurements of electron exchanges.

Various parameters can influence the toxic response to silver nanoparticles (Ag NPs), including the size and surface properties, as well as the exposure environment and the biological site of action. Herein, we assess the intestinal toxicity of three different sizes (10, 40, and 100 nm) of Ag NPs in embryonic zebrafish, and describe the relationship between the properties and behavior of Ag NPs in the exposure medium, and induction of lethal and sublethal effects. We find that the composition of the medium and the size contribute to differential NPs agglomeration, release of Ag ions, and subsequent effects during exposure. The exposure medium causes dramatic reduction in silver dissolution due to the presence of salts and divalent cations, which limits the lethal potential of silver ions. Lethality is observed primarily for embryos exposed to medium sized Ag NPs (40 nm), but not to the supernatant originated from particles, which suggests that the exposure to particulate silver is the main cause of mortality. On the other hand, the exposure to 10 nm and 100 nm NPs, as well as Ag ions, only causes sublethal developmental defects in skeletal muscles and intestine, and induces a nitric oxide imbalance.

Development of fast and sensitive assays for enzyme activity detection has received a great deal of attention because of the wide spread applications in measurements of numerous clinical, food and environmental processes. Herein, a novel amplification approach to enhance the sensitivity of colorimetric assays for detection of β-galactosidase (β-Gal) activity is proposed. β-Gal detection is important in biomedical applications and in food industry, where it is associated with the ripening process of fruits. The method is based on the use of multivalent cerium oxide nanoparticles (CeNPs) which catalyze the oxidation of 4-aminophenol (4-AP) produced in the hydrolysis process of the 4-aminophenyl-β- d -galactopyranoside substrate (4-APG) by β-Gal, thus enhancing detection sensitivity of β-Gal in the visible range. The developed assay is highly sensitive and easy to use. Using the optimized procedure, a limit of detection of 0.06 mU/mL was obtained with a linearity range up to 2.0 mU/mL. The feasibility of the method was demonstrated for detection of β-Gal activity in fruits and the results were compared with the conventional assay, providing over a 30-fold amplification as compared to a commercially available β-Gal protocol. The advantage of the presented assay is its biocatalytic event amplified by a secondary reaction, which enables much more sensitive detection of the enzymatic product. The sensing platform can be applied broadly to a variety of applications that rely on β-Gal activity measurements.

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.

Measurements of neurotransmitter levels are of great physiological and pathological importance and help understanding the state and progression of a variety of neurological diseases. Such studies require the availability of effective methods to probe biochemical processes in real time and allow accurate detection and quantification in vivo. These studies are also important to develop therapies and assess pharmacological effects. However, the presence of neurotransmitters at very low concentrations and variable levels and the complexity of the biological environment pose a great challenge for detection. Electrochemical methods provide real-time measurements in vitro and in vivo. In this presentation, we will discuss design and development of nanomaterials based microbiosensing platforms for the detection of neurotransmitters in vivo, with focus on the monitoring of dopamine, lactate and glutamate. The influence of the electrode design parameters including surface coatings and electrode configurations, and the ability to obtain quantitative spatial and temporal analytical data of the release and distribution of neurotransmitters will be provided with examples of applications. Advantages and limitations of these systems for measurements in real biological environments and the use of oxygen-releasing nanomaterials to address issues related to oxygen limitations and increase sensitivity of measurements in biological environments will be discussed. Our results demonstrate the potential of electrochemical techniques to measure neurotransmitters release in real time and obtain fundamental biochemical-relevant information on physiology, metabolism and disease states in living systems.

Proteins are utilized across many biomedical and pharmaceutical industries; therefore, methods for rapid and accurate monitoring of protein aggregation are needed to ensure proper product quality. Although these processes have been previously studied, it is difficult to comprehensively evaluate protein folding and aggregation by traditional characterization techniques such as atomic force microscopy (AFM), electron microscopy, or X-ray diffraction, which require sample pre-treatment and do not represent native state proteins in solution. Herein, we report early tracking of lysozyme (Lyz) aggregation states by using single-particle collision electrochemistry (SPCE) of silver nanoparticle (AgNP) redox probes. The method relies on monitoring the rapid interaction of Lyz with AgNPs, which decreases the number of single AgNPs available for collisions and ultimately the frequency of oxidative impacts in the chronoamperometric profile. When Lyz is in a non-aggregated monomeric form, the protein forms a homogeneous coverage onto the surface of AgNPs, stabilizing the particles. When Lyz is aggregated, part of the AgNP surface remains uncoated, promoting the agglomeration of Lyz-AgNP conjugates. The frequency of AgNP impacts decreases with increasing aggregation time, providing a metric to track protein aggregation. Visualizations of integrated oxidation charge-transfer data displayed significant differences between the charge transfer per impact for AgNP samples alone and in the presence of non-aggregated and aggregated Lyz with 99% confidence using parametric ANOVA tests. Electrochemical results revealed meaningful associations with UV-vis, circular dichroism, and AFM, demonstrating that SPCE can be used as an alternative method for studying protein aggregation. This electrochemical technique could serve as a powerful tool to indirectly evaluate protein stability and screen protein samples for formation of aggregates.

MXenes are recently developed 2D layered nanomaterials that provide unique capabilities for bioanalytical applications. These include high metallic conductivity, large surface area, hydrophilicity, high ion transport properties, low diffusion barrier, biocompatibility, and ease of surface functionalization. MXenes are composed of transition metal carbides, nitrides, or carbonitrides and have a general formula Mn+1Xn, where M is an early transition metal while X is carbon and/or nitrogen. Due to their unique features, MXenes have attracted significant attention in fields such as clean energy production, electronics, fuel cells, supercapacitors, and catalysis. Their composition and layered structure make MXenes attractive for biosensing applications. The high conductivity allows these materials to be used in the design of electrochemical biosensors and the multilayered configuration makes them an efficient immobilization matrix for the retention of activity of the immobilized biomolecules. These properties are applicable to many biosensing systems and applications. This review describes the progress made on the use and application of MXenes in the development of electrochemical and optical biosensors and highlights future needs and opportunities in this field. In particular, opportunities for developing wearable sensors and systems with integrated biomolecule recognition are highlighted.

With the increased use of nanobiotechnology-enabled solutions for diagnostics, therapeutics, bioelectronics, environmental, and energy-related applications, there exists a great demand for developing manufacturing processes that can reliably and reproducibly generate functional nanostructures with bioactive properties at low cost and in large quantities for implementation in practical devices. Interest in the development of field portable monitoring devices has increased throughout the past decade. Herein we describe fabrication, characterization and performance of portable and printable enzyme biosensors based on functional enzyme–nanoparticle conjugates. We review specific physicochemical and surface properties of nanoparticles used as carriers and sensing components for the design of portable biosensors and describe the role of these parameters in enhancing the performance, stability and field operability of these devices. Assembly of enzyme–nanoparticle conjugates is also discussed with an overview of current and emerging techniques enabling large scale roll-to-roll fabrication and miniaturization, including screen-printing, inkjet and 3D printing methods and their integration in flexible, wearable and inexpensive point-of-use devices. Current status and implementation challenges are provided with examples of applications in the clinical, environmental, public safety and food monitoring fields.

Molecular nanoprobes with intrinsic enzyme-like activity represent a new wave of technology for rapid and sensitive detection of molecular targets. This work reports synthesis and characterization ...

Increased industrial and agricultural activity has affected the availability of phosphorus (P) in nature and has caused a significant imbalance in the P cycle with long-term consequences on ecosystem health and sustainability. While P is an essential element for food production as well as plant and animal nutrition, it is also a limited nonrenewable resource whose availability is expected to decrease in the next century. Widespread application of P-based fertilizers and their excessive accumulation in water bodies leads to eutrophication which is associated with overgrowth of harmful algal blooms and degradation of water quality. This paper provides an overview of contemporary challenges and methodologies for improving P use efficiency and sustainability in the environment. Technologies and processes for the removal of P-containing compounds from water through the use of functional nanomaterial sorbents with tailored surface properties for capture, removal, and recycling are described. Various classes of ...

Chemical mechanical planarization (CMP) is a widely used technique for the manufacturing of integrated circuit chips in the semiconductor industry. The process generates large amounts of waste containing engineered particles, chemical additives, and chemo-mechanically removed compounds. The environmental and health effects associated with the release of CMP materials are largely unknown and have recently become of significant concern. Using a zebrafish embryo assay, we established toxicity profiles of individual CMP particle abrasives (SiO2 and CeO2), chemical additives (hydrogen peroxide, proline, glycine, nicotinic acid, and benzotriazole), as well as three model representative slurries and their resulting waste. These materials were characterized before and after use in a typical CMP process in order to assess changes that may affect their toxicological profile and alter their surface chemistry due to polishing. Toxicity outcome in zebrafish is discussed in relation with the physicochemical characteristics of the abrasive particles and with the type and concentration profile of the slurry components pre and post-polishing, as well as the interactions between particle abrasives and additives. This work provides toxicological information of realistic CMP slurries and their polishing waste, and can be used as a guideline to predict the impact of these materials in the environment.

Cellulose-nanomaterial hybrid systems are promising platforms for the development of portable devices that can be used for fast and inexpensive analysis in the clinical, environmental and food monitoring fields. By combining the chemical and physical properties of the cellulosic network with the unique optical, electrical and catalytic functions of nanomaterials, it is possible to create versatile devices with engineered sensing functions. This review describes the most commonly used types of nanomaterials, their unique properties and assembly in hybrid structures in conjunction with cellulose paper and provides an overview of the most commonly used detection methodologies and their performance for selected applications. Finally, future perspectives and challenges to the implementation of these devices for real world applications are discussed, with focus on method optimization, validation and regulation in order to reach consumers.