Advancement of metal oxide nanomaterials on agri-food fronts.

The application of metal oxide nanomaterials (MOx NMs) in the agrifood industry offers innovative solutions that can facilitate a paradigm shift in a sector that is currently facing challenges in meeting the growing requirements for food production, while safeguarding the environment from the impacts of current agriculture practices. This review comprehensively illustrates recent advancements and applications of MOx for sustainable practices in the food and agricultural industries and environmental preservation. Relevant published data point out that MOx NMs can be tailored for specific properties, enabling advanced design concepts with improved features for various applications in the agrifood industry. Applications include nano-agrochemical formulation, control of food quality through nanosensors, and smart food packaging. Furthermore, recent research suggests MOx's vital role in addressing environmental challenges by removing toxic elements from contaminated soil and water. This mitigates the environmental effects of widespread agrichemical use and creates a more favorable environment for plant growth. The review also discusses potential barriers, particularly regarding MOx toxicity and risk evaluation. Fundamental concerns about possible adverse effects on human health and the environment must be addressed to establish an appropriate regulatory framework for nano metal oxide-based food and agricultural products.

Low-cost goldleaf electrode as a platform for Escherichia coli immunodetection.

Gold electrodes are one of most prevalent substrates in electrochemical biosensors because they can be easily and highly efficiently functionalized with thiolated biomolecules. However, conventional methods to fabricate gold electrodes are costly, time-consuming and require onerous equipment. Here, an affordable method for rapid fabrication of an electrochemical immunosensor for Escherichia coli detection is presented. The gold electrode was generated using 24-karat gold leaves and lowcost polyvinyl chloride adhesive sheets covered with an insulating PTFE layer. The goldleaf electrode (GLE) was patterned using laser ablation and characterized by cyclic voltammetry, electrochemical impedance spectroscopy, scanning electronic microscopy, contact angle and 3D profiling. The GLEs were modified by a self-assembled mercaptopropionic monolayer, followed by surface activation to allow binding of the specific anti-E. coli antibody via carbodiimide linking. The biosensor showed a detection limit of 2 CFU/mL and a linear dynamic range of 10-107 CFU/mL for E. coli cells. No false positive signals were obtained from control bacteria. The obtained results demonstrated suitability of GLE for use in biosensors with high reliability and reproducibility. It is foreseeable that our work will inspire design of point-of-need biosensors broadly applicable in low-resource settings.

A novel approach for amine derivatization of MoS2 nanosheets and their application toward label-free immunosensor.

The application of molybdenum disulfide (MoS2) nanosheets has assumed great significance in the design of next-generation biosensors. The immobilization of biomolecules on MoS2 nanosheets has generally been achieved via hydrophobic interactions or through other complicated surface modifications. In this work, we report a novel strategy for electrochemically assisted amine derivatization of MoS2 nanosheets. This newly proposed approach helped to immobilize the MoS2 nanosheets with antibodies via facile EDC/NHS {N-(3-dimethylaminopropyl)-N-(ethylcarbodiimide/N-hydroxysuccinimide)} cross-linking chemistry. The MoS2 nanosheets were first exfoliated and then electrochemically modified with 2-aminobenzylamine. Through a subsequent bioconjugation of the above amine-derivatized MoS2 nanosheets with anti-prostate-specific antigen (PSA) antibodies, an immunosensing device was realized for the detection of the 'prostate specific antigen'. The application of the proposed immunosensor was characterized with a low detection limit (10-3 ng/mL) over a very wide quantitation range (10-3 to 200 ng/mL).

A comprehensive review on nano-molybdenum disulfide/DNA interfaces as emerging biosensing platforms.

The development of nucleic acid-based portable platforms for the real-time analysis of diseases has attracted considerable scientific and commercial interest. Recently, 2D layered molybdenum sulfide (2D MoS2 from here on) nanosheets have shown great potential for the development of next-generation platforms for efficient signal transduction. Through combination with DNA as a biorecognition medium, MoS2 nanostructures have opened new opportunities to design and construct highly sensitive, specific, and commercially viable sensing devices. The use of specific short ssDNA sequences like aptamers has been proven to bind well with the unique transduction properties of 2D MoS2 nanosheets to realize aptasensing devices. Such sensors can be operated on the principles of fluorescence, electro-cheumuluminescence, and electrochemistry with many advantageous features (e.g., robust biointerfacing through various conjugation chemistries, facile sensor assembly, high stability with regard to temperature/pH, and high affinity to target). This review encompasses the state of the art information on various design tactics and working principles of MoS2/DNA sensor technology which is emerging as one of the most sought-after and valuable fields with the advent of nucleic acid inspired devices. To help achieve a new milestone in biosensing applications, great potential of this emerging technique is described further with regard to sensitivity, specificity, operational convenience, and versatility.

Application of MoS2 modified screen-printed electrodes for highly sensitive detection of bovine serum albumin.

The present work reports the application of a new molybdenum disulphide (MoS2)-based electrochemical platform for highly sensitive quantitation of an iron-binding protein, bovine serum albumin (BSA). The gold screen-printed electrodes were modified with MoS2 nanoflakes, followed by bioconjugation with anti-BSA antibodies. Using the above bioelectrode, cyclic voltammetric analysis was carried out in the presence of a Fe(3+)/Fe(2+) redox probe which exhibited a linear response of peak current with varying concentrations of BSA up to 10 ng/mL (with a detection limit of 0.006 ng/mL). This study is novel in that it shows a considerable enhancement of signal during electrochemical sensing of a protein.

A label-free electrochemical immunosensor for the detection of cardiac marker using graphene quantum dots (GQDs).

A label-free immunosensor based on electrochemical impedance spectroscopy has been developed for the sensitive detection of a cardiac biomarker myoglobin (cMyo). Hydrothermally synthesized graphene quantum dots (GQDs) have been used as an immobilized template on screen printed electrodes for the construction of an impedimetric sensor platform. The GQDs-modified electrode was conjugated with highly specific anti-myoglobin antibodies to develop the desired immunosensor. The values of charge transfer resistance (Rct) were monitored as a function of varying antigen concentration. The Rct value of the immunosensor showed a linear increase (from 0.20 to 0.31kΩ) in the range of 0.01-100ng/mL cMyo. The specific detection of cMyo was also made in the presence of other competing proteins. The limit of detection for the proposed immunosensor was estimated as 0.01ng/mL which is comparable to the standard ELISA techniques.

A New Electrolytic Synthesis Method for Few-Layered MoS2 Nanosheets and Their Robust Biointerfacing with Reduced Antibodies.

We report an efficient method for the synthesis of few-layered MoS2 nanosheets and demonstrate their application in the label-free detection of the prostate-specific antigen (PSA) cancer marker. As a novel strategy, the electro-dissolution of molybdenum metal sheets in the presence of Na(+) and S(2-) ions led to the formation of Na(+) intercalated MoS2. Further exfoliation by ultrasonication yielded the desired formation of few-layered MoS2 nanosheets. After comprehensive characterization, the synthesized MoS2 nanosheets were channeled in a field-effect transistor (FET) microdevice. Chemically reduced anti-PSA antibodies were immobilized on the MoS2 channel above the FET microdevice to construct a specific PSA immunosensor. The antibodies were deliberately reduced to expose the hinge-region disulfide bonds. This approach offered a robust and site-directed immunosensing device through biointerfacing of the sulfhydryl groups (-SH) in the reduced antibody with the surface S atoms of MoS2. This device was validated as an effective immunosensor with a low detection limit (10(-5) ng/mL) over a wide linear detection range (10(-5) to 75 ng/mL).

Formation of High-Purity Indium Oxide Nanoparticles and Their Application to Sensitive Detection of Ammonia.

High-purity In2O3 nanoparticles were recovered from scrap indium tin oxide substrates in a stepwise process involving acidic leaching, liquid-liquid extraction with a phosphine oxide extractant, and combustion of the organic phase. The morphological and structural parameters of the recovered nanoparticles were investigated to support the formation of the desired products. These In2O3 nanoparticles were used for sensitive sensing of ammonia gas using a four-probe electrode device. The proposed sensor offered very quick response time (around 10 s) and highly sensitive detection of ammonia (at a detection limit of 1 ppm).

One step in-situ synthesis of amine functionalized graphene for immunosensing of cardiac marker cTnI.

2-Aminobenzyl amine (2-ABA) functionalized graphene is proposed for the ultrasensitive immunosensing of Cardiac Troponin I (cTnI). 2-ABA was electrochemically polymerized on the graphene decorated interdigitated electrode to obtain the amine functionalized graphene (f-GN). The f-GN electrode was then modified with monoclonal anti-cTnI antibodies via Schiff reaction based chemistry. Detailed characteristics of the processes involved and the finally developed antibody conjugated f-GN interdigitated electrode have been studied. The above micro-device was used in a drain source configuration for the sensing of cTnI. A wide dynamic linear range of antigen detection (0.01-1ng/mL) is achieved with the limit of detection of 0.01ng/mL. The utility of the proposed sensing technique is demonstrated by successfully testing the antigen concentration in spiked serum samples.

Plasmon enhanced fluoro-immunoassay using egg yolk antibodies for ultra-sensitive detection of herbicide diuron.

Plasmon enhanced fluorescence immunoassay (PEFI) format has been reported in developing a sensitive heterogeneous fluoroimmunoassay for monitoring the phenylurea herbicide diuron. Computer-assisted molecular modeling was carried out to study the conformational and electrostatic effects of synthesized hapten for producing highly specific egg yolk antibody against a phenyl urea herbicide diuron. The generated antibodies were labeled with fluorescein isothiocyanate at different molar ratios and used as tracer in the developed fluorescence based immunoassay. The sensitivity of the assay format was enhanced by using silver nanoparticles tagged with bovine serum albumin as a new blocking reagent in the developed PEFI format. Enhancer treatment on the developed immunoassay showed a significant improvement of fluorescence signal intensity with approximately 10 fold increase in assay sensitivity. The immunoassay has a detection limit of 0.01 ng mL(-1) with good signal precision (~2%) in the optimum working concentration range between 1 pg mL(-1) to 10 µg mL(-1) of diuron. These findings facilitate high throughput fluorescence-based processes that could be useful in biology, drug discovery and compound screening applications.

Rapid extraction and quantitative detection of the herbicide diuron in surface water by a hapten-functionalized carbon nanotubes based electrochemical analyzer.

A solid phase extraction micro-cartridge containing a non-polar polystyrene absorbent matrix was coupled with an electrochemical immunoassay analyzer (EIA) and used for the ultra-sensitive detection of the phenyl urea herbicide diuron in real samples. The EIA was fabricated by using carboxylated carbon nanotubes (CNTs) functionalized with a hapten molecule (an amine functionalized diuron derivative). Screen printed electrodes (SPE) were modified with these haptenized CNTs and specific in-house generated anti diuron antibodies were used for bio-interface development. The immunodetection was realized in a competitive electrochemical immunoassay format using alkaline phosphatase labeled secondary anti-IgG antibody. The addition of 1-naphthyl phosphate substrate resulted in the production of an electrochemically active product, 1-naphthol, which was monitored by using differential pulse voltammetry (DPV). The assay exhibited excellent sensitivity and specificity having a dynamic response range of 0.01 pg mL(-1) to 10 µg mL(-1) for diuron with a limit of detection of around 0.1 pg mL(-1) (n = 3) in standard water samples. The micro-cartridge coupled hapten-CNTs modified SPE provided an effective and efficient electrochemical immunoassay for the real-time monitoring of pesticides samples with a very high degree of sensitivity.