Carbon nanotubes and graphene modified screen-printed carbon electrodes as sensitive sensors for the determination of phytochelatins in plants using liquid chromatography with amperometric detection

CuSeO3@f-CNFs: A superoxide nanozyme for the selective nanomolar determination of the key cardiovascular biomarker, Glutathione

Nanocomposites that mimic the characteristics of enzymes, commonly as nanozymes, can function as an efficient sensing material with high selectivity towards the targeted biological macromolecule. These nanozymes overcome of the challenges that arise when using natural enzymes as sensing material. This study presents a novel nanozyme, Copper Selenite (CuSeO3) nanoparticles mounted on f-CNF, to electrochemically determine a potential cardiovascular biomarker, Glutathione (GSH). The choice of this material is due to the well-known ability of GSH to form a complex with copper. When a Cu ion enters a healthy cell, it quickly forms a complex with GSH, which then moves to another storage molecule: either a metalloprotein or a chelator. CNF was functionalized using acid to generate functionalized-CNF to enhance biocompatibility and boost conductivity. This was done to provide many active sites for effective integration of CuSeO3 in the nanocomposite preparation. The glassy carbon electrode (GCE) surface was enhanced by introducing CuSeO3@f-CNF nanocomposite, resulting in a significant increase in the current response for GSH in comparison to prior research. CuSeO3@f-CNF/GCE sensor has shown excellent sensing properties, like enhanced stability, selectivity, sensitivity, and reproducibility, for detecting and quantifying GSH. The sensor demonstrated an extensive linear detection range from 62.5 nM to 7785.0 μM, signifying one of the most comprehensive ranges documented to date. It attained a remarkable detection limit (LOD) of 17.6 nM. The sensor's performance was further tested by analyzing genuine biological fluid samples. The nanozyme-modified GCE demonstrated exceptional electrocatalytic efficiency for GSH detection, making it extremely appropriate for real-time monitoring applications.

Betaine-Modified Green Carbon Dot for Cr(VI) Sensing, in Vivo Cr(VI) Imaging, and Growth Promotion in the Rice Plant

Hexavalent chromium is a toxic environmental pollutant that damages plants due to disruption of nutrient uptake, photosynthesis metabolism, and oxidative stress, which suppresses the growth and development of the plant. In this work, we have developed a betaine-modified carbon dot (BT@CD) sensor for monitoring Cr(VI) in water and plants. Fluorescent carbon dots have been synthesized using jamun juice (Syzygium cumini) as the carbon source subjected to surface modification with betaine (BT@JCD). This BT@JCD exhibits strong blue fluorescence, which significantly decreases in the presence of Cr(VI) due to the inner filter effect in a range of 5-450 nM with a detection limit of 0.033 μM. Due to its easy translocation in the vascular bundles, these fluorescence nanosensors can be applied to detect Cr(VI) in rice plants Oryza sativa) through fluorescence confocal imaging. The treatment of rice plants with BT@JCDs in the concentration range of 0.2 to 1g/mL not only triggered photophysical parameters such as carbohydrates, chlorophyll, and carotenoids but also enhanced the antioxidant enzyme activity promoting plant growth.

An assessment of nanotechnology-based interventions for cleaning up toxic heavy metal/metalloid-contaminated agroecosystems: Potentials and issues

Heavy metals (HMs) are among the most dangerous environmental variables for a variety of life forms, including crops. Accumulation of HMs in consumables and their subsequent transmission to the food web are serious concerns for scientific communities and policy makers. The function of essential plant cellular macromolecules is substantially hampered by HMs, which eventually have a detrimental effect on agricultural yield. Among these HMs, three were considered, i.e., arsenic, cadmium, and chromium, in this review, from agro-ecosystem perspective. Compared with conventional plant growth regulators, the use of nanoparticles (NPs) is a relatively recent, successful, and promising method among the many methods employed to address or alleviate the toxicity of HMs. The ability of NPs to reduce HM mobility in soil, reduce HM availability, enhance the ability of the apoplastic barrier to prevent HM translocation inside the plant, strengthen the plant's antioxidant system by significantly enhancing the activities of many enzymatic and nonenzymatic antioxidants, and increase the generation of specialized metabolites together support the effectiveness of NPs as stress relievers. In this review article, to assess the efficacy of various NP types in ameliorating HM toxicity in plants, we adopted a 'fusion approach', in which a machine learning-based analysis was used to systematically highlight current research trends based on which an extensive literature survey is planned. A holistic assessment of HMs and NMs was subsequently carried out to highlight the future course of action(s).

Carbon nanotubes in plant dynamics: Unravelling multifaceted roles and phytotoxic implications

Carbon nanotubes (CNTs) have emerged as a promising frontier in plant science owing to their unique physicochemical properties and versatile applications. CNTs enhance stress tolerance by improving water dynamics and nutrient uptake and activating defence mechanisms against abiotic and biotic stresses. They can be taken up by roots and translocated within the plant, impacting water retention, nutrient assimilation, and photosynthesis. CNTs have shown promise in modulating plant-microbe interactions, influencing symbiotic relationships and mitigating the detrimental effects of phytopathogens. CNTs have demonstrated the ability to modulate gene expression in plants, offering a powerful tool for targeted genetic modifications. The integration of CNTs as sensing elements in plants has opened new avenues for real-time monitoring of environmental conditions and early detection of stress-induced changes. In the realm of agrochemicals, CNTs have been explored for their potential as carriers for targeted delivery of nutrients, pesticides, and other bioactive compounds. CNTs have the potential to demonstrate phytotoxic effects, detrimentally influencing both the growth and developmental processes of plants. Phytotoxicity is characterized by induction of oxidative stress, impairment of cellular integrity, disruption of photosynthetic processes, perturbation of nutrient homeostasis, and alterations in gene expression. This review aims to provide a comprehensive overview of the current state of knowledge regarding the multifaceted roles of CNTs in plant physiology, emphasizing their potential applications and addressing the existing challenges in translating this knowledge into sustainable agricultural practices.

Recent Advances in Electrochemical Sensors for Sulfur-Containing Antioxidants

Sulfur-containing antioxidants are an important part of the antioxidant defense systems in living organisms under the frame of a thiol-disulfide equilibrium. Among them, l-cysteine, l-homocysteine, l-methionine, glutathione, and α-lipoic acid are the most typical representatives. Their actions in living systems are briefly discussed. Being electroactive, sulfur-containing antioxidants are interesting analytes to be determined using various types of electrochemical sensors. Attention is paid to the chemically modified electrodes with various nanostructured coverages. The analytical capabilities of electrochemical sensors for sulfur-containing antioxidant quantification are summarized and discussed. The data are summarized and presented on the basis of the electrode surface modifier applied, i.e., carbon nanomaterials, metal and metal oxide nanoparticles (NPs) and nanostructures, organic mediators, polymeric coverage, and mixed modifiers. The combination of various types of nanomaterials provides a wider linear dynamic range, lower limits of detection, and higher selectivity in comparison to bare electrodes and sensors based on the one type of surface modifier. The perspective of the combination of chromatography with electrochemical detection providing the possibility for simultaneous determination of sulfur-containing antioxidants in a complex matrix has also been discussed.

Validation and uncertainty estimation of analytical method for quantification of phytochelatins in aquatic plants by UPLC-MS

Phytochelatins (PCs) are peptides that play an important role in homeostasis and detoxification of heavy metal in plants. Furthermore, they have been proposed as earlier potential biomarkers of aquatic pollution by heavy metals. Nowadays, several researchers have reported on current methods for quantification of glutathione (GSH) and the PCs (phytochelatin 2, phytochelatin 3, phytochelatin 4) quantification in plants. However, no method has reported the uncertainty of the measurement, which helps to improve the accuracy and quality assurance in the PC quantification. In this work, a new methodology using ultra-high-performance liquid chromatography coupled to mass spectrometry (UPLC-MS) to measure with high precision and accuracy the PCs in aquatic plants, was validated. Selectivity, linearity, limit of detection, limit of quantification, precision, trueness and uncertainty estimation were examined as parts of the method validation. The described method shows excellent linearity in different ranges for all analytes with coefficients of determination higher than 0.99. The relative standard deviation for intra-day precision was <3% and for inter-day <10%. All LOD and LOQ analytes ranged from 0.02 to 0.08 μg ml^-1, and from 0.03 to 0.09 μg ml^-1, respectively. The recoveries varied from 61% to 89%. In order to obtain an interval of results with the highest confidence levels, the uncertainty associated with the measurements was evaluated. The calibration curve (>50%) and recovery (19-44%) were the most important contributors to the total uncertainty. The proposed method was applied to quantify GSH and PCs in the aquatic plants Lemna gibba L., Myriophyllum heterophyllum Michx., Arenaria paludicola and Hydrocotyle ranunculoides L. fil., showing statistical differences in the mass fraction of the analytes.

Overview and recent advances in electrochemical sensing of glutathione - A review

The present paper is aimed at providing an overview of the recent advances in the electrochemical sensing of glutathione (GSH), an important electrochemically and biologically active molecule, for the period 2012-2018. Herein, the analytical performances of newly developed electrochemical methods, procedures and protocols for GSH sensing are comprehensively and critically discussed with respect to the type of method, electrodes used (new electrode modifications, advanced materials and formats), sample matrices, and basic validation parameters obtained (limit of detection, linear dynamic range, precision, selectivity/evaluation of interferences). This paper considers electrochemical methods used alone as well as the hyphenated methods with electrochemical detection (ECD), such as HPLC-ECD or CE-ECD. The practical applicability of the platforms developed for GSH detection and quantification is mostly focused on pharmaceutical and biomedical analysis. The most significant electrochemical approaches for GSH detection in multicomponent analyte samples and multicomponent matrices and for real-time in vivo GSH analysis are highlighted. The great variability in the electrochemical techniques, electrode approaches, and obtainable performance parameters, discussed in this review, brought new insights not only on current GSH and glutathione disulfide (GSSG) determinations, but, along with this, on the advances in electrochemical analysis from a more general point of view.

Occurrence, toxicity, and speciation analysis of arsenic in edible mushrooms

Owing to the strong concentration and biotransformation of arsenic, the influence of some edible mushrooms on human health has attracted widespread attention. The toxicity of arsenic greatly depends on its species, so the speciation analysis of arsenic is of critical importance. The aim of the present review is to highlight recent advances in arsenic speciation analysis in edible mushrooms. We summarized the contents and distribution of arsenic species in some edible mushrooms, the methods of sample preparation, and the techniques for their identification and quantification. Stability of the arsenic species during sample pretreatment and storage is also briefly discussed.

Characterization and classification of Spanish paprika (Capsicum annuum L.) by liquid chromatography coupled to electrochemical detection with screen-printed carbon-based nanomaterials electrodes

Screen-printed electrodes based on graphite, carbon nanotubes, carbon nanofibers, and graphene were tested as amperometric detectors for the determination of phenolic compounds by high performance liquid chromatography (HPLC). The chromatographic performance as well as the obtained sensitivity, detection and quantification limits suggest that carbon nanofibers modified screen-printed electrode (SPCE-CNF) is the amperometric sensor that provides the best analytical performance. Upon this confirmation, chromatographic data obtained using SPCE-CNF were exploited by means of linear discriminant analysis (LDA) to successfully characterize and classify 96 Spanish paprika (Capsicum annuum L.) samples with different origin and type: from La Vera (including sweet, bittersweet and spicy types) and from Murcia (including sweet and spicy types).

Progress in utilisation of graphene for electrochemical biosensors

This review discusses recent graphene (GR) electrochemical biosensor for accurate detection of biomolecules, including glucose, hydrogen peroxide, dopamine, ascorbic acid, uric acid, nicotinamide adenine dinucleotide, DNA, metals and immunosensor through effective immobilization of enzymes, including glucose oxidase, horseradish peroxidase, and haemoglobin. GR-based biosensors exhibited remarkable performance with high sensitivities, wide linear detection ranges, low detection limits, and long-term stabilities. Future challenges for the field include miniaturising biosensors and simplifying mass production are discussed.

Nanostructured carbon electrode modified with N-doped graphene quantum dots-chitosan nanocomposite: a sensitive electrochemical dopamine sensor

A highly selective and sensitive dopamine electrochemical sensor based on nitrogen-doped graphene quantum dots-chitosan nanocomposite-modified nanostructured screen printed carbon electrode is presented, for the first time. Graphene quantum dots were prepared via microwave-assisted hydrothermal reaction of glucose, and nitrogen doping was realized by introducing ammonia in the reaction mixture. Chitosan incorporation played a significant role towards the selectivity of the prepared sensor by hindering the ascorbic acid interference and enlarging the peak potential separation between dopamine and uric acid. The proposed sensor's performance was shown to be superior to several recently reported investigations. The as-prepared CS/N,GQDs@SPCE exhibited a high sensitivity (i.e. ca. 418 µA mM cm^-2), a wide linear range i.e. (1-100 µM) and (100-200 µM) with excellent correlations (i.e. R² = 0.999 and R² = 1.000, respectively) and very low limit of detection (LOD = 0.145 µM) and limit of quantification (LOQ = 0.482 µM) based on S/N = 3 and 10, respectively. The applicability of the prepared sensor for real sample analysis was tested by the determination of dopamine in human urine in pH 7.0 PBS showing an approximately 100% recovery with RSD < 2% inferring both the practicability and reliability of CS/N,GQDs@SPCE. The proposed sensor is endowed with high reproducibility (i.e. RSD = ca. 3.61%), excellent repeatability (i.e. ca. 0.91% current change) and a long-term stability (i.e. ca. 94.5% retained activity).

Phytochelatin synthesis in response to Hg uptake in aquatic plants near a chlor-alkali factory

The effects of mercury (Hg) released from a chlor-alkali factory in aquatic plants along the Ebro River basin (NE Spain) were analysed considering the phytochelatins (PC_n) and their isoforms content in these plants. These compounds were analyzed using HPLC with amperometric detection, and the macrophytes species Ceratophyllum demersum and Myriopyllum spicatum were collected in two sampling campaigns, autumn and spring, respectively. To correlate the PC_n content in macrophytes with the Hg contamination, analysis of total Hg (THg) content in plants and suspended particulate matter, as well as the dissolved-bioavailable fraction of Hg in water measured by the diffusive gradient in thin film (DGT) technique were done. The results confirm the presence of PC₂-Ala in extracts of C. demersum and PC₂-desGly in M. spicatum, and the concentration of these thiol compounds depends clearly on the distance between the hot spot and the downstream sites: the higher the levels are, the closer the hot spot is. Since most of the Hg is hypothesized to be associated with SPM and transported downstream, our results of the DGT suggest that trace amounts of Hg in water can be released as free metal ions yielding a certain accumulation in plants (reaching the ppb level) that are enough for activation of induction of PCs. A few PCs species have been determined, at different seasons, indicating that they can be used as good indicators of the presence of bioavailable Hg in aquatic media throughout the year.

Simple and Sensitive Colorimetric Detection of Dopamine Based on Assembly of Cyclodextrin-Modified Au Nanoparticles

A controlled assembly of natural beta-cyclodextrin modified Au NPs mediated by dopamine is demonstrated. Furthermore, a simple and sensitive colorimetric detection for dopamine is established by the concentration-dependent assembly.

Polyaniline/graphene quantum dot-modified screen-printed carbon electrode for the rapid determination of Cr(VI) using stopped-flow analysis coupled with voltammetric technique

Polyaniline/graphene quantum dots (PANI/GQDs) were used to modify a screen-printed carbon electrode (SPCE) in a flow-based system. A method for rapidly determining the Cr(VI) concentrations by using stopped-flow analysis has been developed using an Auto-Pret system coupled with linear-sweep voltammetry using the PANI/GQD-modified SPCE. The GQDs, synthesized in a botton-up manner from citric acid, were mixed with aniline monomer in an optimized ratio. The mixture was injected into an electrochemical flow cell in which electro-polymerization of the aniline monomer occurred. Under conditions optimized for determining Cr(VI), wide linearity was obtained in the range of 0.1-10 mg L(-1), with a detection limit of 0.097 mg L(-1). For a sample volume of 0.5 m L, the modified SPCE can be used continuously with a sample-throughput of more than 90 samples per hour. In addition, this proposed method was successfully applied to mineral water samples with acceptable accuracy, and the quantitative agreement was accomplished in deteriorated Cr-plating solutions with a standard traditional method for Cr(VI) detection.

Robust method for the analysis of phytochelatins in rice by high-performance liquid chromatography coupled with electrospray tandem mass spectrometry based on polymeric column materials

A sensitive and robust high-performance liquid chromatography coupled with electrospray tandem mass spectrometry method for the identification and quantification of glutathione and phytochelatins from rice was developed. Homogenized samples were extracted with water containing 100 mM dithiothreitol, and solid-phase extraction using polymer anion exchange resin was employed for sample purification. Chromatography was performed on a polymeric column with acetonitrile and water containing 0.1% formic acid as the mobile phase at the flow rate of 300 μL/min. The limit of quantitation was 6-100 nM. This assay showed excellent linearity for both glutathione and phytochelatins over physiological normal ranges, with correlation coefficients (r) > 0.9976. Recoveries for four biothiols were within the range of 76-118%, within relative standard deviations less than 15%. The intraday precision (n = 7) was 2.1-13.3%, and the interday precision over 15 days was 4.3-15.2%. The optimized method was applied to analyze tissue samples from rice grown using nutrient solutions with three different cadmium concentrations (0, 50, and 100 μM). With increasing cadmium concentrations, the content of phytochelatin 2 and phytochelatin 3 in rice roots increased, in contrast to most phytochelatins, and the content of glutathione in rice stems and roots decreased significantly.