Determination of zearalenone with a glassy carbon electrode modified with nanocomposite consisting of palladium nanoparticles and a conductive polymeric ionic liquid

Electrochemical platform based on molecularly imprinted polymer with zinc oxide nanoparticles and multiwalled carbon nanotubes modified screen-printed carbon electrode for amaranth determination

A novel electrochemical platform for amaranth determination has been developed using a rapid, easy, inexpensive, and portable molecularly imprinted polymer technique. The MIP platform was fabricated by electropolymerizing melamine as monomer in the presence of amaranth as template on the surface of ZnO-MWCNT/SPCE. Then, amaranth was completely eluted, leaving imprinted cavities in the polymeric film that could effectively recognize amaranth in solution. The electrochemical platform based on a molecularly imprinted polymelamine was analyzed by scanning electron microscopy (SEM), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and differential pulse voltammetry (DPV). Under optimum conditions, the developed MIP/ZnO-MWCNT/SPCE platform can be properly used for amaranth determination, with high sensitivity of 96.2 µA µM cm^-2, two linear concentration ranges (0.01 to 1 µM and 1 to 1000 µM) and a low limit of detection of 0.003 µM. The anodic peak potential of amaranth was found to be 0.73 V. Additionally, the polymelamine MIP films specifically recognize amaranth molecules, making it possible to detect amaranth in a complex solution with high selectivity, excellent repeatability, reproducibility, and stability. The MIP/ZnO-MWCNT modified screen-printed carbon electrode was successfully applied to determine amaranth in pharmaceutical and water samples, with recovery values ranging from 99.7 to 102% and RSD% values less than 3.2%.

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.

MoS2 quantum dots and titanium carbide co-modified carbon nanotube heterostructure as electrode for highly sensitive detection of zearalenone

A novel electrochemical sensor has been fabricated for sensitive determination of zearalenone (ZEA) in food samples based on molybdenum disulfide quantum dots (MoS₂ QDs) and two-dimensional titanium carbide (2D-Ti₃C₂T_x MXene) co-modified multi-walled carbon nanotube (MWCNT) heterostructure. Physical and electrochemical characterizations reveal that 2D-Ti₃C₂T_x and MoS₂ QDs co-modified MWCNTs yields synergistic signal amplification effect, together with large specific surface area and excellent conductivity for the heterostructure, endowing the developed sensor with high detection performance to ZEA. Under optimized conditions, the sensor shows a wide linear range from 3.00 to 300 ng mL^-1 and a low limit of detection (LOD) of 0.32 ng mL^-1_, which is far lower than the maximum residue limits (MRLs) settled by the European Commission. In addition, it exhibits excellent selectivity, high reproducibility with a relative standard deviation (RSD) of 1.1%, and good repeatability (RSD 1.1%). In real sample analysis recoveries ranged from 94.8 to 105% showing the proposed electrochemical sensor has high potential in practical applications. This work presents an effective and valuable pathway for the use of novel heterostructure in the biosensing field.

Label-free electrochemical immunosensor based on biocompatible nanoporous Fe3O4and biotin–streptavidin system for sensitive detection of zearalenone

In this study, a sensitive label-free electrochemical immunosensor was designed based on nanoporous Fe₃O₄and a biotin–streptavidin system to specifically detect zearalenone (ZEN).

Strip-shaped Co3O4 as a peroxidase mimic in a signal-amplified impedimetric zearalenone immunoassay

An impedimetric immunoassay was designed for ultrasensitive determination of zearalenone (ZEN). It is making use of the peroxidase-like activity of strip-shaped Co₃O₄ (ssCo₃O₄) which catalyzes the oxidation of 4-chloro-1-naphthol to produce an insoluble precipitate in the presence of H₂O₂. The precipitate is electrically nonconductive and accumulates on the electrode, thereby retarding the electron transfer from the redox probe ferro/ferricyanide to the surface of electrode. This amplifies the impedimetric signal in accordance with logarithm of the concentration of ZEN. The electrode was further modified with TiO₂ mesocrystals (TiO₂ MCs) which improve the capture of more analytes and increase the performance of the immunoassay. Under optimized experimental condition, the impedimetric signal increased linearly with the logarithm of the ZEN concentration range between 0.1 fg·mL^-1 to 10 pg·mL^-1. The detection limit is of 33 ag· mL^-1. Graphical abstractThis work describes an impedimetric immunoassay based on the use of strip-shaped Co3O4 that catalyzes the production of an insoluble precipitate in the presence of H2O2 on the surface of a glassy carbon electrode. The effect was used for signal amplification in an electrochemical immunoassay for zearalenone.

An amperometric zearalenone aptasensor based on signal amplification by using a composite prepared from porous platinum nanotubes, gold nanoparticles and thionine-labelled graphene oxide

The authors constructed a voltammetric zearalenone (ZEN) aptasensor based on use of porous platinum nanotubes, gold nanoparticles (p-PtNTs/AuNPs) and thionine (Thi) labelled graphene oxide (GO). The p-PtNTs were synthesized in-situ based on tellurium nanowires as sacrificial templates. Subsequently, thiol-modified aptamers were self-assembled on the AuNPs that had been electrodeposited on the surface of the modified electrode. The presence of p-PtNTs on the electrode increases the loading with AuNPs and aptamers. It also warrants that the Thi-labelled GO can be assembled onto the aptamer via π interactions. In the presence of ZEN, it will be bound by the aptamer. The GO/Thi conjugate will be released from the aptamer, and this causes a decrease in Thi current. Under the optimal conditions and at a typical working potential of -0.22 V (vs. Ag/AgCl), the method has a linear range that covers the 0.5 pg·mL^-1 to 0.5 μg·mL^-1 ZEN concentraion range and a lower detection limit of 0.17 pg·mL^-1. Graphical abstract Voltammetric zearalenone aptasensor based on use of porous platinum nanotubes/gold nanoparticles and thionine labelled graphene oxide was fabricated for the detection of zearalenone.

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.

Progress on nanostructured electrochemical sensors and their recognition elements for detection of mycotoxins: A review

Nanomaterial-embedded sensors have been developed and applied to monitor various targets. Mycotoxins are fungal secondary metabolites that can exert carcinogenic, mutagenic, teratogenic, immunotoxic, and estrogenic effects on humans and animals. Consequently, the need for the proper regulation on foodstuff and feed materials has been recognized from times long past. This review provides an overview of recent developments in electrochemical sensors and biosensors employed for the detection of mycotoxins. Basic aspects of the toxicity of mycotoxins and the implications of their detection are comprehensively discussed. Furthermore, the development of different molecular recognition elements and nanomaterials required for the detection of mycotoxins (such as portable biosensing systems for point-of-care analysis) is described. The current capabilities, limitations, and future challenges in mycotoxin detection and analysis are also addressed.

Fluorometric lateral flow immunochromatographic zearalenone assay by exploiting a quencher system composed of carbon dots and silver nanoparticles

It is found that the fluorescence of carbon dots (CD) with an emission peak at 459 nm is strongly quenched by silver nanoparticles (AgNPs) with their absorption peak at 430 nm. The finding was applied in a fluorescence quenchometric lateral flow immunochromatographic assay for detection of zearalenone (ZEN) with CDs conjugated to ovalbumin (OVA) as donor signal probe and AgNP-Ab as acceptor signal probe. The assay has an LOD of 0.1 μg·L^-1 for ZEN. This is 10 times better than the respective "turn-off" AgNP-based LFIA. In case of cereal samples and their products, the LODs range from 1 to 2.5 μg·kg^-1. Only minor cross reactivity is found for fusarium toxins, and no cross-sensitivity for aflatoxin B1, T-2 mycotoxin, ochratoxin A, deoxynivalenol, and fumonisin B1. The assay represents a simple, sensitive, and rapid tool for determination of ZEN in cereal samples and their products. Graphical abstract Schematic presentation of fluorescence quenching lateral flow immunochromatographic assay (FLFIA) based on carbon dots (CD) and silver nanoparticle (AgNP) fluorescence resonance energy transfer (FRET) system for the rapid high sensitive detection of zearalenone (ZEN) in cereal samples.

Novel Colorimetric Aptasensor for Zearalenone Detection Based on Nontarget-Induced Aptamer Walker, Gold Nanoparticles, and Exonuclease-Assisted Recycling Amplification

Zearalenone (ZEN) toxicity is a significant risk for human beings. Thus, it is of high importance to develop sensitive, precise, and inexpensive analytical methods for ZEN detection, especially in human serum. Here, a colorimetric aptasensor is presented for the determination of ZEN based on the nontarget-induced aptamer walker, catalytic reaction of gold nanoparticles (AuNPs), exonuclease III (Exo III) as a signal amplifier, and 4-nitrophenol as a colorimetric agent. Low amount of ZEN requirement and signal amplification are some of the distinct advantages of the proposed aptasensor. In the absence of ZEN, the aptamer (Apt) starts walking on the AuNP surface with the help of Exo III and binds to multiple complementary strands of aptamer, leading to the change of sample color from yellow to colorless. Upon the addition of ZEN, both the Apt and complementary strand exist as single-stranded DNAs on the surface of AuNPs, resulting in less access of 4-nitrophenol to the surface of AuNPs and less catalytic performance of AuNPs. In this situation, the color of the sample remains yellow (the color of 4-nitrophenol). The presented aptasensor was capable to detect ZEN in a wide linear dynamic range, 20-80 000 ng/L, with a detection limit of 10 ng/L. The prepared sensing strategy was successfully used for ZEN determination in the human serum sample.

Developments in mycotoxin analysis: an update for 2015-2016

This review summarises developments in the determination of mycotoxins over a period between mid-2015 and mid-2016. Analytical methods to determine aflatoxins, Alternaria toxins, ergot alkaloids, fumonisins, ochratoxins, patulin, trichothecenes and zearalenone are covered in individual sections. Advances in proper sampling strategies are discussed in a dedicated section, as are methods used to analyse botanicals and spices and newly developed liquid chromatography mass spectrometry based multi-mycotoxin methods. This critical review aims to briefly discuss the most important recent developments and trends in mycotoxin determination as well as to address limitations of presented methodologies.