Single-use sensor technology for monitoring of zearalenone in foods: ZentoSens

Smartphone-Controlled Aptasensor for Voltammetric Detection of Patulin in Apple Juice

Patulin (PAT) is a mycotoxin that adversely affects the health of humans and animals. PAT can be particularly found in products such as apples and apple juice and can cause many health problems if consumed. Therefore, accurate and sensitive determination of PAT is very important for food quality and human and animal health. A voltammetric aptasensor was introduced in this study for PAT determination while measuring the changes at redox probe signal. The limit of detection (LOD) was found to be 0.18 pg/mL in the range of 1-104 pg/mL of PAT in buffer medium under optimum experimental conditions. The selectivity of the PAT aptasensor against ochratoxin A, fumonisin B1 and deoxynivalenol mycotoxins was examined and it was found that the aptasensor was very selective to PAT. PAT determination was performed in an apple juice medium for the first time by using a smartphone-integrated portable device, and accordingly, an LOD of 0.47 pg/mL was achieved in diluted apple juice medium. A recovery range of 91.24-93.47% was obtained for PAT detection.

Electro-oxidation sensing of sumatriptan in aqueous solutions and human blood serum by Zn(II)-MOF modified electrochemical delaminated pencil graphite electrode

An electrochemical sensory platform is presented for determination of sumatriptan (SUM) in aqueous solutions and human blood serum. A pencil graphite electrode (PGE) was electrochemically delaminated by cyclic voltammetry technique, and then further modified using nanoparticles of a zinc-based metal-organic framework (Zn(II)-MOF). The fabricated Zn(II)-MOF/EDPGE electrode was utilized for sensitive electrochemical detection of SUM via an electro-oxidation reaction. The Zn(II)-MOF was hydrothermally synthesized and characterized by various techniques. The electrochemical delamination of PGE results in a porous substrate, facilitating the effective immobilization of the modifier. The designed sensor benefits from both enhanced surface area and an accelerated electron transfer rate, as evidenced by the chronocoulogram and Nyquist plots. Under optimized conditions, the developed sensor exhibited a linear response for 0.99-9.52 µM SUM solutions. A short response time of 5 s was observed for the fabricated sensor and the detection limit was found to be 0.29 μM. Selectivity of Zn(II)-MOF/EDPGE towards SUM was evaluated by examining the interference effect of codeine, epinephrine, acetaminophen, ascorbic acid, and uric acid, which are commonly found in biological samples. The developed sensor shows excellent performance with recovery values falling within the range of 96.6 to 111% for the analysis of SUM in human blood serum samples.

Electrochemical aptasensor based on exonuclease III-mediated signal amplification for sensitive detection of vomitoxin in cornmeal

Vomitoxin (DON) residues in grains are of great concern to public health. Herein, a label-free aptasensor was constructed to detect DON distributed in grains. Cerium-based metal-organic framework composite gold nanoparticles (CeMOF@Au) were used as substrate materials to facilitate electron transfer and provided more binding sites for DNA. The separation of DON-aptamer (Apt) complex and cDNA was achieved by magnetic separation technique based on magnetic beads (MBs), ensuring the specificity of the aptasensor. Exonuclease III (Exo III)-assisted cDNA cycling process strategy would be triggered when cDNA was separated and introduced to the sensing interface for further signal amplification. Under optimal conditions, the constructed aptasensor presented a wide detection range from 1 × 10^-8 mg·mL^-1 to 5 × 10^-4 mg·mL^-1 for DON, and the detection limit was 1.79 × 10^-9 mg·mL^-1, including a satisfactory recovery in cornmeal sample spiked with DON. The results showed that the proposed aptasensor had high reliability and promising application potential in detecting DON.

Construction of AuNPs/reduced graphene nanoribbons co-modified molecularly imprinted electrochemical sensor for the detection of zearalenone

In this work, a highly sensitive and selective molecularly imprinted electrochemical sensor is exploited to detect zearalenone (ZEA) by the synergistic effect of reduced graphene nanoribbons (rGNRs) and gold nanoparticles (AuNPs). The oxidized GNRs are firstly produced by an improved Hummers' oxidation method, and then reduced and modified together with AuNPs onto a glassy carbon electrode by electrodeposition technique to realize collaborative amplification of electrochemical signal. The molecularly imprinted polymer film with specific recognition sites can be generated on the modified electrode by electropolymerization. The effect of experimental conditions is systematically investigated to obtain the best detection performance. It is found that the constructed sensor shows a wide linear range of 1-500 ng·mL^-1 for ZEA with a detection limit as low as 0.34 ng·mL^-1. Obviously, our constructed molecularly imprinted electrochemical sensor shows great potential in the application of precisely detecting ZEA in food.

Low-Cost High-Resolution Potentiostat for Electrochemical Detection of Nucleic Acids and Biomolecular Interactions

A handheld USB-powered instrument developed for the electrochemical detection of nucleic acids and biomolecular interactions is presented. The proposed instrument is capable of scanning ± 2.25 V while measuring currents up to ±10 mA, with a minimum current resolution of 6.87 pA. Therefore, it is suitable for nucleic acid sensors, which have high background currents. A low-cost microcontroller with an on-chip 16-bit analog-to-digital converter, 12-bit digital-to-analog converter, and a built-in USB controller were used to miniaturize the system. The offset voltages and gain errors of the analog peripherals were calibrated to obtain a superior performance. Thus, a similar performance to those of the market-leader potentiostats was achieved, but at a fraction of their cost and size. The performance of the application of this proposed architecture was tested successfully and was found to be similar to a leading commercial device through a clinical application in the aspects of the detection of nucleic acids, such as calf thymus ssDNA and dsDNA, and their interactions with a protein (BSA) by using single-use graphite electrodes in combination with the differential pulse voltammetry technique.

Detection and electrocatalytic mechanism of zearalenone using nanohybrid sensor based on copper-based metal-organic framework/magnetic Fe3O4-graphene oxide modified electrode

A novel and simple strategy was proposed for the determination of ZEA in breakfast cereal, maize powder and rice flour using an electrochemical nanohybrid sensor based on copper-based metal-organic framework (Cu-MOF)/magnetic Fe₃O₄-graphene oxide (Fe₃O₄-GO) modified electrode fabricated by the layer-by-layer assembled technique. The synthesized Cu-MOF with high porosity favorably improved the effective surface area and the analytical performance of nanohybrid sensing electrode. The crafted sensor has large surface area, high electron transfer, and satisfactory efficiency. ZEA was electrochemically detected in a wide linear range from 159.2 to 2865.2 ng mL^-1 with LOD of 23.14 ng mL^-1 under the optimal conditions. Moreover, the electrocatalytic mechanism of ZEA oxidation was proposed by density functional theory (DFT). A favorable energetic interaction was presented when Cu-MOF adsorbed on Fe₃O₄-GO, and a small new band appeared on the Fermi level energy (E_f) that facilitated the electron transfer between bands.

Detection of Senecionine in Dietary Sources by Single-Use Electrochemical Sensor

Pyrrolizidine alkaloids (PAs) are produced by plants as secondary compounds that are the most widely distributed natural toxins. There have been many cases of human toxicity caused by consumption of toxic plant species, as herbal teas and grain or grain products contaminated with PA-containing seeds have been reported. Companies that produce dried spices and tea leaves should examine the PA level in their products. For the first time in the literature, a simple and inexpensive electrochemical assay based on a single-use sensor was introduced for quantitative determination of senecionine (SEN) in the most frequently contaminated food sources. SEN was immobilized on a pencil graphite electrode surface by the passive adsorption technique. Differential pulse voltammetry (DPV) was used to evaluate the oxidation signal of SEN, which was observed to be around +0.95 V. The oxidation signal was specific to the SEN in the sample, and the current value was proportional to its concentration. The selectivity of our assay was also tested in the presence of other similar PAs such as intermedine, lycopsamine, and heliotrine. The detection limit is calculated by developed assay and found to be 5.45 µg/mL, which is an acceptable concentration value of SEN occurring at toxic levels for consumers. As an application of the developed sensor in food products, the electrochemical detection of SEN was successfully performed in flour and herbal tea products.

Recent Advances in Conventional Methods and Electrochemical Aptasensors for Mycotoxin Detection

The presence of mycotoxins in foodstuffs and feedstuffs is a serious concern for human health. The detection of mycotoxins is therefore necessary as a preventive action to avoid the harmful contamination of foodstuffs and animal feed. In comparison with the considerable expense of treating contaminated foodstuffs, early detection is a cost-effective way to ensure food safety. The high affinity of bio-recognition molecules to mycotoxins has led to the development of affinity columns for sample pre-treatment and the development of biosensors for the quantitative analysis of mycotoxins. Aptamers are a very attractive class of biological receptors that are currently in great demand for the development of new biosensors. In this review, the improvement in the materials and methodology, and the working principles and performance of both conventional and recently developed methods are discussed. The key features and applications of the fundamental recognition elements, such as antibodies and aptamers are addressed. Recent advances in aptasensors that are based on different electrochemical (EC) transducers are reviewed in detail, especially from the perspective of the diagnostic mechanism; in addition, a brief introduction of some commercially available mycotoxin detection kits is provided.

Recent advances in electrochemical monitoring of zearalenone in diverse matrices

The current manuscript summarizes different electrochemical sensing systems developed within the last 5 years for the detection of zearalenone (ZEN) in diverse matrices such as food, feed, and biofluids. ZEN is one of the most prevalent non-steroidal mycotoxins that is often found in pre- and post-harvest crops. Crops contamination with ZEN and animal exposure to it via contaminated feed, is a global health and economic concern. The European Union has established various preventive programs to control ZEN contamination, and regulations on the maximum levels of ZEN in food and feed. Electrochemical (bio)sensors are a very promising alternative to sensitive but sophisticated and expensive chromatographic techniques. In the current review, recent developments towards electrochemical sensing of ZEN, sorted by type of transducer, their design, development, and approbation/validation are discussed, and the use of specialized electrochemical instrumentation is highlighted.

Development of a multi-channel magnetic bead micro-probe assay for high-throughput detection of zearalenone in edible and medicinal Coix seed

A multi-channel magnetic bead micro-probes assay (MBPA) based on indirect competitive principle was developed for high-throughput detection of zearalenone (ZEA) in edible and medicinal Coix seed. This strategy introduced magnetic beads as the carriers, the specific primary antibodies as the capture probes for targets and the secondary antibodies functionalized goat anti-mouse immunoglobulin G labeled fluorescein isothiocyanate as the fluorescence signal probes. Through the competitive reaction of ZEA in Coix seed samples and that covalently coupled on the surface of MBs with their specific antibodies, as well as fast magnetic separation and sensitive fluorescence detection, the developed MBPA strategy allowed low limit of detection (2.03 ng/mL) with broad dynamic range (2.03-440.67 ng/mL), as well as excellent accuracy with the average recovery rate of 96.39% and relative standard deviation (RSD) of 5.48% for ZEA. 36 samples could realize simultaneous analysis in one operation within less than 20 min only needing 50 μL of solution and 30 s of sampling, avoiding large consumption of time and organic solvents. Multiple centrifugation and cleanup steps were omitted because of magnetic separation, avoiding the loss of targets. Diverse capture and fluorescent probes can be randomly bound onto the surface of MBs, making the MBPA strategy a promising tool for on-site high-throughput monitoring of various trace hazard factors in food safety, and environmental monitoring.

Voltammetric behavior of mycotoxin zearalenone at a single walled carbon nanotube screen-printed electrode

A voltammetric method at a single walled carbon nanotube screen-printed electrode was applied for the determination of zearalenone in food samples.