Highly selective and sensitive colorimetric detection for glyphosate based on β-CD@DNA-CuNCs enzyme mimics

Dual-Mode Detection of Glyphosate Based on DNAzyme-Mediated Click Chemistry and DNAzyme-Regulated CeO2 Peroxidase-like Activity

In this article, a dual-signal sensor for the fluorescence and colorimetric detection of glyphosate (Gly) is developed based on DNAzyme-mediated click chemistry and DNAzyme-regulated CeO2 peroxidase-like activity. DNAzyme can bind to Cu+, triggering a click chemistry reaction between 3-Azido-7-hydroxycoumarin (AHC) and 3-ethyn-1-ol (BOL), thus generating a strong fluorescence signal at 475 nm. Due to the strong coordination between Gly and Cu2+, the amount of reduced Cu+ decreases, resulting in a weakening of the fluorescence. In addition, Gly can inhibit the catalytic site of CeO2 enzyme activity, while DNAzyme, which does not participate in the click chemistry reaction, can be adsorbed by CeO2, further inhibiting the enzyme activity and reducing the oxidation color change of 3,3',5,5'-tetramethylbenzidine (TMB). The fluorescence detection limit of this dual-mode sensing platform is 0.15 μg/mL, and the colorimetric detection limit is 0.19 μg/mL. This method has been successfully applied to the detection of Gly in tap water and soybeans, which has a promising application in pesticide residue detection.

Exploring Nucleic Acid Nanozymes: A New Frontier in Biosensor Development

With the growing interest in nucleic acids and nanozymes, nucleic acid nanozymes (NANs) have emerged as a promising alternative to traditional enzyme catalysts, combining the advantages of nucleic acids and nanomaterials, and are widely applied in the field of biosensing. This review provides a comprehensive overview of recent studies on NAN-based biosensors. It classifies NANs based on six distinct enzymatic activities: peroxidase-like, oxidase-like, catalase-like, superoxide dismutase-like, laccase-like, and glucose oxidase-like. This review emphasizes how the catalytic activity of nanozymes is significantly influenced by the properties of nucleic acids and explores the regulatory mechanisms governing the catalytic activity of NANs. Additionally, it systematically reviews important research progress on NANs in colorimetric, fluorescent, electrochemical, SERS, and chemiluminescent sensors, offering insights into the development of the NAN field and biosensor applications.

An electrochemiluminescent dual-signal immunosensor based on a Ru(bpy)32+-doped silica nanoparticle/copper nanocluster composite for okadaic acid detection

In this study, a sensitive dual-signal electrochemiluminescence (ECL) immunosensor was developed for okadaic acid (OA) detection utilizing copper nanoclusters (CuNCs) and Ru(bpy)32+-doped silica nanoparticles (RuSiNPs). Interestingly, the CuNCs could simultaneously enhance both cathodic (-0.95 V) and anodic (+1.15 V) ECL signals of RuSiNPs, forming a dual-signal ECL sensing platform. Further, RuSiNPs@CuNCs were used as immunomarkers by covalently conjugating them with an anti-OA monoclonal antibody (mAb) to form probes. Finally, dual ECL signals of the immunosensor were fabricated and showed good linear relationships with OA concentrations in the range of 0.05-70 ng mL-1, having a median inhibitory concentration (IC50) of 1.972 ng mL-1 and a limit of detection of 0.039 ng mL-1. Moreover, the constant ratio of the cathodic and anodic ECL peaks achieved self-calibration of the detection signal and improved the reliability of the results. Finally, we successfully applied the ECL sensor to detect OA in spiked oyster samples.

DNA Framework-Templated Synthesis of Copper Cluster Nanozyme with Enhanced Activity and Specificity

Nanozymes have been developed to overcome the inherent limitations of natural enzymes, such as their low stability and high cost. However, their efficacy has been hindered by their relatively low specificity and activity. Here, we demonstrate the self-assembly of individual copper nanoclusters (CuNCs) via a simple yet fast (10 min) DNA nanosheet (DNS)-templated method, enhancing the peroxidase-like activity and specificity of CuNCs. Furthermore, we demonstrate the successful assembly of CuNCs on different DNA nanostructures by atomic force microscopy (AFM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The resulting micron-scale ultrathin DNA nanosheet-templated CuNCs (DNS@CuNCs) exhibit exceptional catalytic activity, with a specific activity reaching 1.79 × 103 U mg-1. Investigation into the catalytic process reveals that the enhanced activity and specificity arise from disparities in active intermediate content before and after CuNCs assembly. Significantly, the DNS@CuNCs-based biosensor demonstrates remarkable anti-interference capabilities, enabling the detection of H2O2 in undiluted human serum for the first time with a detection limit of 0.99 μM.

Applications of nanomaterials with enzyme-like activity for the detection of phytochemicals and hazardous substances in plant samples

Plants such as herbs, vegetables, fruits, and cereals are closely related to human life. Developing effective testing methods to ensure their safety and quantify their active components are of significant importance. Recently, nanomaterials with enzyme-like activity (known as nanozymes) have been widely developed in various assays, including colorimetric, fluorescence, chemiluminescence, and electrochemical analysis. This review presents the latest advances in analyzing phytochemicals and hazardous substances in plant samples based on nanozymes, including some active ingredients, organophosphorus pesticides, heavy metal ions, and mycotoxins. Additionally, the current shortcomings and challenges of the actual sample analysis were discussed.

Sensitive colorimetric and fluorescence dual-mode detection of thiophanate-methyl based on spherical Fe3O4/GONRs composite nanozyme

Pesticide detection based on nanozyme is largely limited in terms of the variety of pesticides. Herein, a spherical and well-dispersed Fe3O4/graphene oxide nanoribbons (Fe3O4/GONRs) composite nanozyme was applied to firstly develop an enzyme-free and sensitive colorimetric and fluorescence dual-mode detection of thiophanate-methyl (TM). The synthesized Fe3O4/GONRs possess excellent dual enzyme-like activities (peroxidase and catalase) and can catalyze H2O2 to oxidize 3,3',5,5'-tetramethylbenzidine (TMB) into oxidized TMB (oxTMB). We found that Fe3O4/GONRs can adsorb TM through the synergistic effect of multiple forces, thereby inhibiting the catalytic activities of nanozyme. This inhibition can modulate the transformation of TMB to oxTMB, producing dual responses of absorbance decrease (oxTMB) and fluorescence enhancement (TMB). The limits of detection (LODs) of TM were 28.1 ng/mL (colorimetric) and 8.81 ng/mL (fluorescence), respectively. Moreover, the developed method with the recoveries of 94.8-100.8% also exhibited a good potential application in the detection of pesticides residues in water and food samples.

Dendritic-like MXene quantum dots@CuNi as an efficient peroxidase candidate for colorimetric determination of glyphosate

Oxidized MXene quantum dots@CuNi bimetal (MQDs@CuNi) were firstly prepared through a simple hydrothermal method. Compared to the controlled samples, MQDs@CuNi1:1 showed the highest peroxidase-like activity. The catalytic mechanism of MQDs@CuNi1:1 was investigated using a steady-state fluorescence analysis, which showed that MQDs@CuNi1:1 efficiently decomposes H2O2 and produces highly reactive hydroxyl radicals (OH). Furthermore, theoretical calculations showed that the remarkable catalytic activity of MQDs@CuNi1:1 originates from the interaction between CuNi bimetal and MQDs to promote the activation and decomposition of H2O2, making it easier to combine with the hydrogen at the end of 3,3',5,5'-Tetramethylbenzidine (TMB). Accordingly, a sensitive colorimetric sensor is proposed to detect glyphosate (Glyp), displaying a low detection limit of 1.13 µM. The work will provide a new way for the development of high-performance nanozyme and demonstrate potential applicability for the determination of pesticide residues in environment.

Recent Advances of DNA-Templated Metal Nanoclusters for Food Safety Detection: From Synthesis, Applications, Challenges, and Beyond

Food safety concerns have become a significant threat to human health and well-being, catching global attention in recent years. As a result, it is imperative to research conceptually novel biosensing and effective techniques for food matrices detection. Currently, DNA-templated metal nanoclusters (DNA-MNCs) are considered as one of the most promising nanomaterials due to their excellent properties in biosensing. While DNA-MNCs have garnered increasing interest, the reviews of design strategies, applications, and futuristic prospects for biosensing have been hardly found especially in food safety. The synthesis of DNA-MNCs and their use as biosensing materials in food contamination detection, including pathogenic bacteria, toxins, heavy metals, residues of pesticides, and others were comprehensively reviewed. In addition, we summarize the properties of DNA-MNCs briefly and discuss the challenges and future trends. The application of DNA-MNCs powered biosensing has been demonstrated and actively studied, which is a promising paradigm for food safety testing that can supplement or even replace current existing methods. Despite the challenges of difficulty regulating accurately, poor stability, low quantum yield, and difficult commercial transformation, the application prospects of DNA-MNCs biosensors are promising. This review aims to provide insights and directions for the future development of DNA-MNCs based food detection technology.

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

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

Hazardous impacts of glyphosate on human and environment health: Occurrence and detection in food

With the ever-increasing human population, farming lands are decreasing every year, therefore, for effective crop management; agricultural scientists are continually developing new strategies. However, small plants and herbs always impart a much loss in the yields of the crop and farmers are using tons of herbicides to eradicate that problem. Across the world, several herbicides are available in the market for effective crop management, however, scientists observed various environmental and health effects of the herbicides. Over the past 40 years, the herbicide glyphosate has been used extensively with the assumption of negligible effects on the environment and human health. However, in recent years, concerns have increased globally about the potential direct and indirect effects on human health due to the excessive use of glyphosate. As well, the toxicity on ecosystems and the possible effects on all living creatures have long been at the center of a complex discrepancy about the authorization for its use. The World Health Organization also further classified glyphosate as a carcinogenic toxic component and it was banned in 2017 due to numerous life-threatening side effects on human health. In the present era, the residues of banned glyphosate are more prevalent in agricultural and environmental samples which are directly affecting human health. Various reports revealed the detailed extraction process of glyphosate from different categories of the food matrix. Therefore, in the present review, to reveal the importance of glyphosate monitoring in the food matrix, we discussed the environmental and health effects of glyphosate with acute toxicity levels. Also, the effect of glyphosate on aquatic life is discussed in detail and various detection methods such as fluorescence, chromatography, and colorimetric techniques from different food samples with a limit of detection values are revealed. Overall, this review will give an in-depth insight into the various toxicological aspects and detection of glyphosate from food matrix using various advanced analytical techniques.

Sensitive and Label-Free Colorimetric Detection of Glyphosate Based on the Suppression Peroxidase-Mimicking Activity of Cu(II) Ions

The sensitive and accurate determination of glyphosate (Glyp) is urgently demanded because it is closely correlated with human health and environmental safety. In this work, we proposed a sensitive and convenient colorimetric assay by employing copper ion peroxidases for the detection of Glyp in the environment. Free Cu(II) ions displayed high peroxidase activity and can catalytically oxidize the colorless 3,3',5,5'-tetramethylbenzidine (TMB) into blue oxTMB, resulting in an obviously visible discoloration reaction. Once the Glyp is added, the ability of copper ions to mimic peroxidase can be largely suppressed because of the generation of Glyp-Cu2+ chelate. The favorable selectivity and sensitivity were demonstrated in the colorimetric analysis of Glyp. Furthermore, this rapid and sensitive method was successfully applied in the accurate and reliable determination of glyphosate in the real sample, holding promising applications in pesticide determination in the environment.

A versatile platform for colorimetric, fluorescence and photothermal multi-mode glyphosate sensing by carbon dots anchoring ferrocene metal-organic framework nanosheet

Concerns regarding pesticide residues have driven attempts to exploit accurate, prompt and straightforward approaches for food safety pre-warning. Herein, a nanozyme-mediated versatile platform with multiplex signal response (colorimetric, fluorescence and temperature) was proposed for visual, sensitive and portable detection of glyphosate (GLP). The platform was constructed based on a N-CDs/FMOF-Zr nanosensor that prepared by in situ anchoring nitrogen-doped carbon dots onto zirconium-based ferrocene metal-organic framework nanosheets. The N-CDs/FMOF-Zr possessed excellent peroxidase (POD)-like activity and thus could oxide colorless 3, 3', 5, 5'-tetramethylbenzidine (TMB) into a blue oxidized TMB (oxTMB) in presence of H₂O₂. Intriguingly, owing to the blocking effect triggered by multiple interaction between GLP and N-CDs/FMOF-Zr, its POD-like activity of the latter was remarkably suppressed, which can modulate the transformation of TMB into oxTMB, generating tri-signal responses of fluorescence enhancement, absorbance and temperature decrease. More significantly, the temperature mode can be facilely realized by a portable home-made mini-photothermal device and handheld thermometers. The proposed multimodal sensing was capable of providing sensitive results by fluorescence mode and simultaneously realized visual/portable testing by colorimetric and photothermal channels. Consequently, it exhibited more adaptability for practical applications, which can satisfy different testing requirements according to sensitivity and available instruments/meters, presenting a new horizon for exploiting multifunctional sensors.

An “on-off-on” fluorescence probe for glyphosate detection based on Cu2+ modulated g-C3N4 nanosheets

The analysis of glyphosate is essential to agricultural production, environment protection and public health. Herein, we proposed a fast and convenient “on-off-on” fluorescence platform for sensitive detection of glyphosate via Cu²⁺ modulated g-C₃N₄ nanosheets. The fluorescence of the system was quenched by Cu²⁺. With the presence of glyphosate, the fluorescence could be restored due to the formation of Cu²⁺- glyphosate complex. The proposed method was cost-effective with label-free and enzyme-free. Moreover, it exhibits high sensitivity with a low detection limit of 0.01 μg/ml. Furthermore, the proposed method has been successfully monitored glyphosate in real samples.