TiO2 Nanolayer-Enhanced Fluorescence for Simultaneous Multiplex Mycotoxin Detection by Aptamer Microarrays on a Porous Silicon Surface

Simultaneously Selective Separation of Zearalenone and Four Aflatoxins From Rice Samples Using Co-Pseudo-Template Imprinted Polymers With MIL-101(Cr)-NH2 as Core

A novel approach for the simultaneous separation of zearalenone (ZEN) and four types of aflatoxins (AFB1, AFB2, AFG1 and AFG2) from rice samples was presented. This approach utilized modified MIL-101(Cr)-NH2 as core, with molecularly imprinted polymers (MIPs) serving as the shell. The MIL-101(Cr)-NH2 was prepared via ring-opening reaction, while the imprinted polymers were synthesized using warfarin and 4-methylumbelliferyl acetate as co-pseudo template, ethylene glycol dimethacrylate as the cross-linker and azobisisobutyronitrile as initiator. The resulting co-pseudo-template-MIPs (CPT-MIPs) were thoroughly characterized and evaluated. Adsorption studies demonstrate that the adsorption process of CPT-MIPs follows a chemical monolayer adsorption mechanism, with imprinted factors ranging from 1.24 to 1.52 and selective factors ranging from 1.29 to 1.52. Self-made columns were prepared, and the method for separation was developed and validated. The limit of detections ranged from 0.12 to 2.09 μg/kg, and the limit of qualifications ranged from 1.2 to 6.25 μg/kg. To assess the reliability of the method, ZEN and AFs were spiked at three different levels, and the recoveries ranged from 79.53 to 94.58%, with relative standard deviations of 2.90-5.78%.

Multiplex Aptamer-Based Fluorescence Assay Using Magnetism-Encoded Nanoparticles for Simultaneous Detection of Multiple Pathogenic Bacteria

Multiplex assay has emerged as a robust and versatile method for the simultaneous detection of multiple analytes in a single test. However, challenges in terms of poor accuracy and complexity remained. In this work, we developed a multiplex aptamer-based fluorescence assay using magnetism-encoded nanoparticles for the simultaneous detection of multiple pathogenic bacteria. The encapsulation of different amounts of Fe3O4 nanoparticles in zeolitic imidazolate framework-90 (ZIF-90) leads to the formation of Fe3O4@ZIF-90 (FZ) composites with distinct magnetism strengths. By functionalizing a specific aptamer on the surface of the FZ composites, target bacteria can be specifically and precisely separated from a mixed sample in a sequential manner. This property allows for the simultaneous quantitative analysis of multiple target bacteria by using a single-color fluorescence label, thereby resulting in minimal spectral crosstalk interference and improved accuracy. The successful determination of multiple bacteria in contaminated milk samples demonstrates the applicability of this multiplex assay in complex biological matrices. Compared to conventional multiplex fluorescence assays, this approach offers distinct advantages of simplicity, efficiency, and implementation. We believe that this study can provide valuable insights into the development of the multiplex assay while introducing a new method for the simultaneous detection of multiple bacteria.

Tetrahedral DNA Nanostructure-Engineered Paper-Based Electrochemical Aptasensor for Fumonisin B1 Detection Coupled with Au@Pt Nanocrystals as an Amplification Label

Fumonisin B1 (FB1), as one of the highest toxicity mycotoxins, poses a serious threat to animal and human health, even at low concentrations. It is significant and challenging to develop a sensitive and reliable analytical device. Herein, a paper-based electrochemical aptasensor was designed utilizing tetrahedral DNA nanostructures (TDNs) to controllably anchor an aptamer (Apt), improving the recognition efficiency of Apt to its target. First, gold nanoparticles (AuNPs)@MXenes were used as a sensing substrate with good conductivity and modified on the electrode for immobilization of complementary DNA-TDNs (cDNA-TDNs). In the absence of FB1, numerous Apt-Au@Pt nanocrystals (NCs) was hybridized with cDNA and assembled on the sensing interface, which accelerated the oxidation of TMB with H2O2 and produced a highly amplified differential pulse voltammetry (DPV) signal. When the target FB1 specifically bound to its Apt, the electrochemical signal was decreased by releasing the Apt-Au@Pt NCs from double-stranded DNA (dsDNA). On account of the strand displacement reaction by FB1 triggering, the aptasensor had a wider dynamic linear range (from 50 fg/mL to 100 ng/mL) with a lower limit of detection (21 fg/mL) under the optimized conditions. More impressively, the designed FB1 aptasensor exhibited satisfactory performance in corn and wheat samples. Therefore, the TDN-engineered sensing platform opens an effective approach for sensitive and accurate analysis of FB1, holding strong potential in food safety and public health.

Bio-based material-edible rosemary induced biodegradation of aflatoxin B1 via altering endogenous protective enzymes signatures in animal-derived foods

Aflatoxin B1 (AFB1) is the most hazardous mycotoxin, posing risks to public health. Utilization of bio-based materials to biodegrade AFB1 is a green strategy to overcome this issue. The investigation aimed to screen for endogenous protective enzymes in bio-based material-edible rosemary based on ultra-high performance liquid chromatography coupled to hybrid quadrupole-Orbitrap high-resolution mass spectrometry (UHPLC-Q-Orbitrap HRMS)-proteomics and ascertain their impacts on the biodegradation and biotransformation of AFB1, and the trade-offs of multilevel metabolism of the animal-derived foods through untargeted metabolomics. The proteomics results verified that bio-based material-edible rosemary (0.20%, w/w) significantly up-regulated glutathione S-transferase and stimulated the down-regulation of cytochrome P450 1A2 levels via activating AhR nuclear translocation in rosemary-pickled AFB1-contaminated goat meat. Metabolomics results demonstrated that edible rosemary substantially increased histidine and glutathione implicated in the antioxidant status of goat meat. More importantly, edible rosemary with high endogenous protective enzyme content could efficiently biodegrade AFB1 in goat meat. We first unveiled that rosemary could not only efficiently biodegrade AFB1 up to 90.20% (20.00-1.96 μg kg^-1) but also elevate the bio-ingestion quality of goat meat. These findings suggest that the bio-based material-rosemary is an efficient and environmentally friendly approach for biodegrading AFB1 and elevating the bio-ingestion composition of goat meat.

Label-Free Electrochemical Aptasensor Based on the Vertically-Aligned Mesoporous Silica Films for Determination of Aflatoxin B1

Herein we report a highly specific electrochemical aptasenseor for AFB1 determination based on AFB1-controlled diffusion of redox probe (Ru(NH₃)₆³⁺) through nanochannels of AFB1-specific aptamer functionalized VMSF. A high density of silanol groups on the inner surface confers VMSF with cationic permselectivity, enabling electrostatic preconcentration of Ru(NH₃)₆³⁺ and producing amplified electrochemical signals. Upon the addition of AFB1, the specific interaction between the aptamer and AFB1 occurs and generates steric hindrance effect on the access of Ru(NH₃)₆³⁺, finally resulting in the reduced electrochemical responses and allowing the quantitative determination of AFB1. The proposed electrochemical aptasensor shows excellent detection performance in the range of 3 pg/mL to 3 μg/mL with a low detection limit of 2.3 pg/mL for AFB1 detection. Practical analysis of AFB1 in peanut and corn samples is also accomplished with satisfactory results by our fabricated electrochemical aptasensor.

An enhanced fluorescent sensor system based on molecularly imprinted polymer chips with silver nanoparticles for highly-sensitive zearalenone analysis

A novel enhanced fluorescent sensor system for zearalenone (ZON) determination in flour samples is presented. The ZON-selective molecularly imprinted polymer (MIP) films were developed with a computational modelling method and synthesised with cyclododecyl-2,4-dihydroxybenzoate as a "dummy" template and ethylene glycol methacrylate phosphate as a functional monomer acted as the selective recognition elements for ZON fluorescence detection. Spherical silver nanoparticles (AgNPs) were embedded in the MIP films' structure to enhance the sensor sensitivity. The imprinted films showed a high ZON recognition ability compared to non-imprinted films. Various factors that affected the measurement of the analysed sample were investigated and optimised. Embedding the AgNPs in the MIP films' structure led to an enhanced sensitivity (up to a 200-fold decrease of LOD) compared to unmodified MIP films. This fluorescent sensor system provided ZON analysis with high sensitivity, specificity, and a wider linear dynamic range of 5 ng mL^-1 to 25 μg mL^-1. An enhanced fluorescent sensor system based on MIP chips with embedded AgNPs could detect trace amounts of ZON in foods and feedstuffs with high sensitivity and selectivity.

Microfluidic Biosensor Integrated with Signal Transduction and Enhancement Mechanism for Ultrasensitive Noncompetitive Assay of Multiple Mycotoxins

To achieve high-throughput ultrasensitive detection of mycotoxins in food, a functional DNA-guided transition-state CRISPR/Cas12a microfluidic biosensor (named FTMB) was successfully constructed. The signal transduction CRISPR/Cas12a strategy in FTMB has utilized DNA sequences with a specific recognition function and activators to form trigger switches. Meanwhile, the transition-state CRISPR/Cas12a system was constructed by adjusting the composition ratio of crRNA and activator to achieve a high response for low concentrations of target mycotoxins. On the other hand, the signal enhancement of FTMB has efficiently integrated the signal output of quantum dots (QDs) with the fluorescence enhancement effect of photonic crystals (PCs). The construction of universal QDs for the CRISPR/Cas12a system and PC films matching the photonic bandgap produced a significant signal enhancement by a factor of 45.6. Overall, FTMB exhibited a wide analytic range (10^-5-10¹ ng·mL^-1), low detection of limit (fg·mL^-1), short detection period (∼40 min), high specificity, good precision (coefficients of variation <5%), and satisfactory practical sample analysis capacity (the consistency with HPLC at 88.76%-109.99%). It would provide a new and reliable solution for the rapid detection of multiple small molecules in the fields of clinical diagnosis and food safety.

An aptamer-functionalized photonic crystal sensor for ultrasensitive and label-free detection of aflatoxin B1

As a novel optical responsive material, photonic crystal is a promising sensing material in the recognition and detection of small molecules. Herein, a label-free composite sensor for aflatoxin B1 (AFB1) based on aptamer-functionalized photonic crystal arrays was successfully developed. Three-dimensional photonic crystals (3D PhCs) with a controllable number of layers were produced by a layer-by-layer (LBL) approach, and the introduction of gold nanoparticles (AuNPs) facilitated the immobilization procedure of recognition element aptamers, thus creating the AFB1 sensing detection system (AFB1-Apt 3D PhCs). The sensing system AFB1-Apt 3D PhCs exhibited a good linearity in the wide range of 1 pg mL^-1-100 ng mL^-1 AFB1 with a limit of detection (LOD) of 0.28 pg mL^-1. Furthermore AFB1-Apt 3D PhC was successfully applied in the determination of AFB1 in the millet and beer samples with good recovery. The sensing system performed ultrasensitive and label-free detection to the target, which could be further applied in the fields of food safety, clinical diagnosis or environmental monitoring, establishing an efficient and rapid universal detection platform.

Recent Progress in Development and Application of DNA, Protein, Peptide, Glycan, Antibody, and Aptamer Microarrays

Microarrays are one of the trailblazing technologies of the last two decades and have displayed their importance in all the associated fields of biology. They are widely explored to screen, identify, and gain insights on the characteristics traits of biomolecules (individually or in complex solutions). A wide variety of biomolecule-based microarrays (DNA microarrays, protein microarrays, glycan microarrays, antibody microarrays, peptide microarrays, and aptamer microarrays) are either commercially available or fabricated in-house by researchers to explore diverse substrates, surface coating, immobilization techniques, and detection strategies. The aim of this review is to explore the development of biomolecule-based microarray applications since 2018 onwards. Here, we have covered a different array of printing strategies, substrate surface modification, biomolecule immobilization strategies, detection techniques, and biomolecule-based microarray applications. The period of 2018–2022 focused on using biomolecule-based microarrays for the identification of biomarkers, detection of viruses, differentiation of multiple pathogens, etc. A few potential future applications of microarrays could be for personalized medicine, vaccine candidate screening, toxin screening, pathogen identification, and posttranslational modifications.

Construction of hybridization chain reaction induced optical signal directed change of photonic crystals-DNA hydrogel sensor and its visual determination for aflatoxin B1

Herein, we have introduced hybridization chain reaction (HCR) into the photonic crystals (PhCs) hydrogel, for the first time, realizing HCR for inducing the change of the optical signal of PhCs hydrogel and using this hydrogel as a sensor for determination of the aflatoxin B1 (AFB1). By using specific sequences as the cross-linker, the extension of the cross-linker by HCR drives the swelling of the hydrogel, and the optical property of 2D PhCs array converts this swelling into a change of the Debye diffraction ring. Moreover, by further selecting the aptamer to construct the cross-linker, the hydrogel is also endowed with a unique capability for AFB1, making the hydrogel a novel sensor based on the signal amplification strategy. The results show that the designed hairpin DNAs can effectively trigger the HCR and cause the swelling of hydrogel, and the hydrogel sensor has a good determination performance and high specific recognition for AFB1.

A Novel Fluorescent Aptasensor Based on Dual-labeled DNA Nanostructure for Simultaneous Detection of Ochratoxin A and Aflatoxin B1

Based on DNA strand replacement reaction and aptamer-specific recognition, a simple dual-labeled DNA nanostructure is designed for the simultaneous detection of Ochratoxin A (OTA) and aflatoxin B1 (AFB₁). C1 is labeled with Cy3 and Cy5, while C2 and C3 are labeled with BHQ2. The fluorescence intensity of DNA nanostructure composed of C1, C2 and C3 is weak because of fluorescence resonance energy transfer. When OTA Aptamer (OTA-Apt) and AFB1 Aptamer (AFB₁-Apt) are added to the homogeneous system at the same time, C1 can be replaced with the help of toehold strand displacement, resulting in fluorescence enhancement. In the presence of both OTA and AFB₁, the toehold strand displacement reaction is inhibited due to preferential binding between the target and their corresponding aptamers. The limit of detection of OTA was 0.007 ng/mL and that of AFB₁ was 0.03 ng/mL. The recoveries of OTA and AFB₁ were 96%-101% and 97%-101% in the corn sample, and 99%-101% and 92%-106% in the wine sample. Compared with other sensors, the preparation of this aptasensor needs simpler experimental steps and a shorter total-preparing time, confirming the convenient, rapid, and time-saving operation process.

Label-Free Fluorescence Quantitative Detection Platform on Plasmonic Silica Photonic Crystal Microsphere Array

We have demonstrated the proof-of-concept of a label-free fluorescence quantitative detection platform based on gold nanoparticle (AuNP) enhancement intrinsic fluorescence of protein on the silica photonic crystal microsphere (SPCM) array. The label-free one-step competitive fluorescence immunoassay protocol has been proposed on the surface of the SPCM. Aflatoxin B₁ (AFB₁) as a model molecule was detected by the newly established method. AFB₁-bovine serum albumin and monoclonal antibodies (Abs) of anti-AFB₁ have been immobilized on the surfaces of SPCMs and AuNPs, respectively. AuNPs remarkably enhanced the intrinsic fluorescence of artificial antigens on the surface of the SPCM at near UV excitation. The simulation of electric field distribution showed that the maximum value of the near-field enhancement |E/E₀| of the SPCM with AuNPs could reach 20. The label-free fluorescence enhancement effect comes from the synergistic effects of photonic crystal effect and AuNP plasmon effect. Such a label-free fluorescence detection method can provide a linear detection range from 0.1 to 10 ng/mL with a limit of detection of 0.025 ng/mL and good specificity for AFB₁. The recovery rates in the spiked cereal samples were measured in the range of 84.07 ± 5.71%-101.02 ± 5.13%, which were consistent with that of the traditional enzyme linked immunosorbent assay method. The label-free detection platform displays great application potential in biology, medicine, agriculture, food industry, chemical industry, energy source, and environmental protection.

Nanomaterial-Based Fluorescent Biosensor for Food Safety Analysis

Food safety issues have become a major threat to public health and have garnered considerable attention. Rapid and effective detection methods are crucial for ensuring food safety. Recently, nanostructured fluorescent materials have shown considerable potential for monitoring the quality and safety of food because of their fascinating optical characteristics at the nanoscale. In this review, we first introduce biomaterials and nanomaterials for food safety analysis. Subsequently, we perform a comprehensive analysis of food safety using fluorescent biosensors based on nanomaterials, including mycotoxins, heavy metals, antibiotics, pesticide residues, foodborne pathogens, and illegal additives. Finally, we provide new insights and discuss future approaches for the development of food safety detection, with the aim of improving fluorescence detection methods for the practical application of nanomaterials to ensure food safety and protect human health.

Advances in functional photonic crystal materials for the analysis of chemical hazards in food

Chemical contaminants in food generally include natural toxins (mycotoxins, animal toxins, and phytotoxins), pesticides, veterinary drugs, environmental pollutants, heavy metals, and illegal additives. Developing a low-cost, simple, and rapid detection technology for harmful substances in food is urgently needed. Analytical methods based on different advanced materials have been developed into rapid detection methods for food samples. In particular, photonic crystal (PC) materials have a unique surface periodic structure, structural color, a large surface area, easy integration with photoelectronic and magnetic devices which have great advantages in the development of rapid, low-cost, and highly sensitive analytical methods. This review focuses on the PC materials in the view of their fabrication processes, functionalized recognition components for the specific recognition of hazardous substances, and applications in the separation, enrichment, and detection of chemical hazards in real samples. Suspension array based on three-dimensional PC microspheres by droplet-based microfluidic assembly is a great promising and powerful platform for food safety detection fields. For the PCs selective analysis, biological antibodies, aptamers, and molecularly imprinted polymers (MIPs) could be modified for specific recognition of target substances, particularly MIPs because of their low-cost and easy mass production. Based on these functional PCs, various toxic and hazardous substances can be selectively enriched or recognized in real samples and further quantified in combination of liquid chromatography method or optical detection methods including fluorescence, chemiluminescence, and Raman spectroscopy.

Spectral-Free Double Light Detection of DNA Based on a Porous Silicon Bragg Mirror

To improve the detection sensitivity of a porous silicon optical biosensor in the real-time detection of biomolecules, a non-spectral porous silicon optical biosensor technology, based on dual-signal light detection, is proposed. Double-light detection is a combination of refractive index change detection and fluorescence change detection. It uses quantum dots to label probe molecules to detect target molecules. In the double-signal-light detection method, the first detection-signal light is the detection light that is reflected from the surface of the porous silicon Bragg mirror. The wavelength of the detection light is the same as the wavelength of the photonic band gap edge of the porous silicon Bragg mirror. CdSe/ZnS quantum dots are used to label the probe DNA and hybridize it with the target DNA molecules in the pores of porous silicon to improve its effective refractive index and enhance the detection-reflection light. The second detection-signal light is fluorescence, which is generated by the quantum dots in the reactant that are excited by light of a certain wavelength. The Bragg mirror structure further enhances the fluorescence signal. A digital microscope is used to simultaneously receive the digital image of two kinds of signal light superimposed on the surface of porous silicon, and the corresponding algorithm is used to calculate the change in the average grey value before and after the hybridization reaction to calculate the concentration of the DNA molecules. The detection limit of the DNA molecules was 0.42 pM. This method can not only detect target DNA by hybridization, but also detect antigen by immune reaction or parallel biochip detection for a porous silicon biosensor.

Simple and programmed three-dimensional DNA tweezer for simultaneous one-step detection of ochratoxin A and zearalenone

Three-dimensional (TD) deoxyribonucleic acid (DNA) tweezers were programmed for one-step identification and detection of ochratoxin A (OTA) and zearalenone (ZEN). The unfolding of the TD-DNA tweezers by aptamers specific to these two mycotoxins "turned" the fluorescent signals "on." The bonding of the aptamers to their corresponding targets in OTA and ZEN "turned" the fluorescent signals and the DNA tweezers "off." The detection limit of the TD-DNA tweezers for OTA and ZEN was 0.032 and 0.037 ng mL^-1, respectively. The feasibility of this method was tested using two samples. Detection via this method increased the recovery of OTA and ZEN from 95.8% to 110.2%. Spike recovery and certified food products were used to detect applicability in actual situations. Analyte detection in complex samples using TD-DNA tweezers is rapid, as the process involves a single operational step. This proposed design has considerable potential for application in mycotoxin detection.

Partial induced reorientation of 5CB in a liquid crystal microarray and a signal-on sensing assay for the detection of aflatoxin B1

Herein, a signal-on liquid crystal microarray (LCM) sensor is designed for the first time with a micro-spectral optical sensing signal. Depending on the change of the orientation of the LC molecules in the LCM films and the intensity of the spectral peaks of the PhCs, the signal-on LCM biosensor achieves the detection of AFB1 and the Partial Response Mechanism (PSM) of the LCM films is discovered.

High-Throughput Aptamer Microarrays for Fluorescent Detection of Multiple Organophosphorus Pesticides in Food

A novel high-throughput aptamer microarray fluorescent method based on thioflavin T (ThT) was established for the sensitive detection of phoxim, parathion, fensulfothion, and isocarbophos. In this work, the aptamers in binding buffer tended to have the antiparallel G-quadruplex structure, which can bind ThT and release its potential fluorescence signal. However, when the organophosphorus pesticides (OPs) were present, partial aptamers preferred to bind them, forcing the displacement of ThT from the G-quadruplex and resulting in the significant decrease in fluorescence signal. Under optimal experimental conditions (12T spacer, 300 nM aptamer, and 80 μM ThT), the OP aptamer microarray has low limits of detection of 25.4 ng/mL for phoxim, 12.0 ng/mL for parathion, 7.7 ng/mL for fensulfothion, and 9.9 ng/mL for isocarbophos. The accuracy and reliability of the method is further verified by testing the recovery rate of OPs spiked in two different complicated sample matrices (pears and radishes). It is worth mentioning that not only the developed aptamer microarray technology has low sensitivity and a broad spectrum, but it also allows for high-throughput and rapid analysis of a variety OPs, which overcomes some of the shortcomings of other OP detection methods.

Signal enhancing strategies in aptasensors for the detection of small molecular contaminants by nanomaterials and nucleic acid amplification

Small molecular contaminants (such as mycotoxins, antibiotics, pesticide residues, etc.) in food and environment have given rise to many biological and ecological toxicities, which has attracted worldwide attention in recent years. Meanwhile, due to the advantages of aptamers such as high specificity and stability, easy synthesis and modification, as well as low cost and immunogenicity, various aptasensors for the detection of small molecular contaminants have been flourishing. An aptasensor as a whole is composed of an aptamer-based target recognizer and a signal transducer, which are fields of concentrated research. In the practical detection applications, in order to achieve the quantitative detection of small molecular contaminants at low abundance in real samples, a large number of signal enhancing strategies have been utilized in the development of aptasensors. Recent years is a vintage period for efficient signal enhancing strategies of aptasensors by the aid of nanomaterials and nucleic acid amplification that are applied in the elements for target recognition and signal conversion. Therefore, this paper meticulously reviews the signal enhancing strategies based on nanomaterials (including the (quasi-)zero-dimensional, one-dimensional, two-dimensional and three-dimensional nanomaterials) and nucleic acid amplification (including enzyme-assisted nucleic acid amplification and enzyme-free nucleic acid amplification). Furthermore, the challenges and future trends of the abovementioned signal enhancing strategies for application are also discussed in order to inspire the practitioners in the research and development of aptasensors for small molecular contaminants.

Mycotoxins—Prevention, Detection, Impact on Animal Health

Mycotoxins are defined as secondary metabolites of some species of mold fungi. They are present in many foods consumed by animals. Moreover, they most often contaminate products of plant and animal origin. Fungi of genera Fusarium, Aspergillus, and Penicillum are most often responsible for the production of mycotoxins. They release toxic compounds that, when properly accumulated, can affect many aspects of breeding, such as reproduction and immunity, as well as the overall liver detoxification performance of animals. Mycotoxins, which are chemical compounds, are extremely difficult to remove due to their natural resistance to mechanical, thermal, and chemical factors. Modern methods of analysis allow the detection of the presence of mycotoxins and determine the level of contamination with them, both in raw materials and in foods. Various food processes that can affect mycotoxins include cleaning, grinding, brewing, cooking, baking, frying, flaking, and extrusion. Most feeding processes have a variable effect on mycotoxins, with those that use high temperatures having the greatest influence. Unfortunately, all these processes significantly reduce mycotoxin amounts, but they do not completely eliminate them. This article presents the risks associated with the presence of mycotoxins in foods and the methods of their detection and prevention.

An Aptamer-Array-Based Sample-to-Answer Biosensor for Ochratoxin A Detection via Fluorescence Resonance Energy Transfer

Food toxins are a hidden threat that can cause cancer and tremendously impact human health. Therefore, the detection of food toxins in a timely manner with high sensitivity is of paramount importance for public health and food safety. However, the current detection methods are relatively time-consuming and not practical for field tests. In the present work, we developed a novel aptamer-chip-based sample-to-answer biosensor (ACSB) for ochratoxin A (OTA) detection via fluorescence resonance energy transfer (FRET). In this system, a cyanine 3 (Cy3)-labeled OTA-specific biotinylated aptamer was immobilized on an epoxy-coated chip via streptavidin-biotin binding. A complementary DNA strand to OTA aptamer at the 3′-end was labeled with a black hole quencher 2 (BHQ2) to quench Cy3 fluorescence when in proximity. In the presence of OTA, the Cy3-labeled OTA aptamer bound specifically to OTA and led to the physical separation of Cy3 and BHQ2, which resulted in an increase of fluorescence signal. The limit of detection (LOD) of this ACSB for OTA was 0.005 ng/mL with a linearity range of 0.01–10 ng/mL. The cross-reactivity of ACSB against other mycotoxins, ochratoxin B (OTB), aflatoxin B1 (AFB1), zearalenone (ZEA), or deoxynilvalenol (DON), was less than 0.01%. In addition, this system could accurately detect OTA in rice samples spiked with OTA, and the mean recovery rate of the spiked-in OTA reached 91%, with a coefficient of variation (CV) of 8.57–9.89%. Collectively, the ACSB may represent a rapid, accurate, and easy-to-use platform for OTA detection with high sensitivity and specificity.

A Novel Multiplex Mycotoxin Surface-Enhanced Raman Spectroscopy Immunoassay Using Functional Gold Nanotags on a Silica Photonic Crystal Microsphere Biochip

A novel multiplex mycotoxin surface-enhanced Raman spectroscopy (SERS) immunoassay was established for the first time on different artificial antigen-modified silica photonic crystal microspheres (SPCMs), which can be integrated into a biochip array to achieve multiplex detection using corresponding antibody-functionalized gold nanoparticles (AuNPs) as the SERS nanotag. The unique optical structure of SPCMs is helpful to find the detection spots easily, accommodate a large amount of probe molecules, and enhance the Raman signal intensity. Such enhancement was confirmed by the simulation result, showing the electric field enhancing effect in SPCMs with AuNPs being 7 times. A competitive SERS immunoassay was established using antigen-modified SPCMs and mycotoxins to compete for binding antibody-functionalized SERS nanotags, displaying broad linear detection ranges of 0.001-0.1 ng/mL for aflatoxin B₁ (AFB₁), 0.01-10 ng/mL for ochratoxin A (OTA), and 0.001-0.1 ng/mL for zearalenone (ZEN) and low detection limits of 0.82 pg/mL for AFB₁, 1.43 pg/mL for OTA, and 1.00 pg/mL for ZEN. In the spiked cereal samples, recovery rates of the method were measured in the range of 70.35-118.04% for the three mycotoxins, which was in agreement with that of the traditional enzyme-linked immunosorbent assay method. The SERS immunoassay for mycotoxin detection also showed high specificity and good repeatability and reproducibility. The new microsphere-based SERS immunoassay biochip only requires a one-step reaction and overcomes the disadvantages of fluorescence and chemiluminescence background signals. The work paves the way for further developing SERS-based microsphere suspension arrays for new targets.

A novel fluorescent aptasensor based on exonuclease-assisted triple recycling amplification for sensitive and label-free detection of aflatoxin B1

Aflatoxins are the most toxic type of mycotoxins, which may cause serious carcinogenesis, teratogenesis, and mutagenesis to humans and animals. In this work, we demonstrate a novel label-free fluorescent aptasensor based on exonuclease-assisted triple recycling amplification for the sensitive detection of aflatoxin B1 (AFB1). With the close cooperation of T7 exonuclease and three elaborately designed hairpin probes, the target AFB1 can perform three consecutive cycles of amplification reactions. In this process, each hairpin probe is fully utilized, and the target AFB1, the secondary target and the tertiary target are recycled, thereby achieving a high amplification. Interestingly and importantly, the secondary and tertiary targets generated by amplification are also excellent DNA template sequences for silver nanoclusters (AgNCs). In the presence of NaBH₄ and AgNO₃, a great number of DNA-AgNCs are synthesized, thereby producing a strong fluorescent signal. Under optimal conditions, the developed aptasensor exhibited high sensitivity to AFB1 with a low detection limit of 0.19 pg mL^-1 and a wide dynamic range of 1 × 10^-6-1 μg mL^-1. In addition, the aptasensor also performed well in the determination of AFB1 in real samples.

A dual-colored persistent luminescence nanosensor for simultaneous and autofluorescence-free determination of aflatoxin B1 and zearalenone

Mycotoxins contamination in agricultural products poses a serious threat to human and animal health, so rapid and sensitive nanosensors for simultaneous determination of multiple mycotoxins in food samples are highly desirable for food safety monitoring. Herein, we report the fabrication of functional dual-colored persistent luminescence nanoparticles (PLNPs) in conjunction with Fe₃O₄ magnetic nanoparticles as a nanosensor for the simultaneous biosensing of aflatoxin B₁ (AFB₁) and zearalenone (ZEN) in food samples. Two types of PLNPs with a single excitation wavelength, Zn₂GeO₄:Mn²⁺ and Zn_1.25Ga_1.5Ge_0.25O₄:Cr³⁺,Yb³⁺,Er³⁺, are employed as the signal units, and aptamers with high affinity and specificity to the corresponding mycotoxins are used as the recognition units. The nanosensor was fabricated by hybridizing the aptamer modified PLNPs with the complementary DNA modified Fe₃O₄. The developed nanosensor offers the integrated merits of autofluorescence-free detection of persistent luminescence, the high specificity of aptamer and the high speed of magnetic separation, allowing highly sensitive and selective detection of AFB₁ and ZEN in food samples with the limits of detection of 0.29 pg mL^-1 for AFB₁ and 0.22 pg mL^-1 for ZEN and the recoveries of 93.6%-103.2% for AFB₁ and 94.7%-105.1% for ZEN. This work also provides a novel universal PLNPs-based optical platform for the simultaneous detection of multiple contaminants in complex samples.

Aptamer-based detection of fumonisin B1: A critical review

Mycotoxin contamination is a current issue affecting several crops and processed products worldwide. Among the diverse mycotoxin group, fumonisin B1 (FB1) has become a relevant compound because of its adverse effects in the food chain. Conventional analytical methods previously proposed to quantify FB1 comprise LC-MS, HPLC-FLD and ELISA, while novel approaches integrate different sensing platforms and fluorescently labelled agents in combination with antibodies. Nevertheless, such methods could be expensive, time-consuming and require experience. Aptamers (ssDNA) are promising alternatives to overcome some of the drawbacks of conventional analytical methods, their high affinity through specific aptamer-target binding has been exploited in various designs attaining favorable limits of detection (LOD). So far, two aptamers specific to FB1 have been reported, and their modified and shortened sequences have been explored for a successful target quantification. In this critical review spanning the last eight years, we have conducted a systematic comparison based on principal component analysis of the aptamer-based techniques for FB1, compared with chromatographic, immunological and other analytical methods. We have also conducted an in-silico prediction of the folded structure of both aptamers under their reported conditions. The potential of aptasensors for the future development of highly sensitive FB1 testing methods is emphasized.

A potential-resolved electrochemiluminescence resonance energy transfer strategy for the simultaneous detection of neuron-specific enolase and the cytokeratin 19 fragment

An electrochemiluminescence resonance energy transfer (ECL-RET) immunosensor was developed based on the potential-resolved technology for the simultaneous detection of neuron-specific enolase (NSE) and the cytokeratin 19 fragment (CYFRA21-1). The absorption spectrum of gold nanorods (AuNRs) perfectly overlapped with the ECL spectra of SnS2@Pt and Ru(bpy)32+/Zn-MOF, so they exhibited an excellent ECL-RET effect with high efficiency. Zn-MOF possesses a large surface area, which allows for the loading of Ru(bpy)32+. This results in a signal probe of Ru(bpy)32+/Zn-MOF/Ab1 showing a strong ECL emission. Simultaneously, owing to the excellent electronic conductivity of PtNPs, they can increase the electron transfer rate between S2O82- and tin disulfide nanoflowers (SnS2NFs). Hence, the ECL signal of SnS2NFs can be enhanced. Under the optimal conditions, the linear range for NSE is 0.2 pg mL-1-20 ng mL-1 with a detection limit of 79 fg mL-1. The linear range for CYFRA21-1 is 1.25 pg mL-1-12.5 ng mL-1 with a detection limit of 0.43 pg mL-1. The proposed immunosensor can be used for the sensitive simultaneous detection of NSE and CYFRA21-1 in human serum and has promise for clinical diagnostics.

Highly Sensitive Simultaneous Detection of Multiple Mycotoxins Using a Protein Microarray on a TiO2-Modified Porous Silicon Surface

A new protein microarray method for multiplex mycotoxin detection in parallel has been established on a stable TiO₂-modified porous silicon (PSi) surface. A typical competitive immunoassay microarray protocol has been developed for simultaneous detection of multiplex mycotoxins including aflatoxin B₁ (AFB₁), ochratoxin A (OTA), and fumonisin B₁ (FB₁) on the TiO₂-PSi surface. The epoxy groups were selected to modify the surface of a TiO₂-PSi wafer for the immobilization of artificial antigens of mycotoxins because of their high signal-to-noise ratios. Under optimal conditions, the developed method showed wide linear detection ranges of 0.01-1 ng/mL for OTA, 0.001-1 ng/mL for AFB₁, and 0.01-1 ng/mL for FB₁ and low limit of detections (LODs) of 0.433 ng/mL for OTA, 0.243 ng/mL for AFB₁, and 0.093 ng/mL for FB₁. The microarray method can specifically identify the three mycotoxins and their analogues. The recovery rates in real samples were within 75-120%, which were in agreement with that of the classical ELISA method. The new method has great application potential for rapid, sensitive, and high-throughput screening of multiplex mycotoxins and other target molecules.

Application of Multiplexed Aptasensors in Food Contaminants Detection

The existence of contaminants in food poses a serious threat to human health. In recent years, aptamer sensors (aptasensors) have been developed rapidly for the detection of food contaminants because of their high specificity, design flexibility, and high efficiency. However, the development of high-throughput, highly sensitive, on-site, and cost-effective methods for simultaneous detection of food contaminants is still restricted due to multiple signal overlap or mutual interference and cross-reaction between different analytes with similar molecular structures. To overcome these problems, this Review summarizes some effective strategies from the articles published in recent years about multiplexed aptasensors for the simultaneous detection of food contaminants. This work focuses on the application of multiplexed aptasensors to simultaneously detect antibiotics, pathogens, and mycotoxins in food. These aptasensors mainly contain fluorescent aptasensors, electrochemical aptasensors, surface-enhanced Raman scattering-based aptasensors, microfluidic chip aptasensors, and paper-based multiplexed aptasensors. In addition, this Review also covers the application of nucleic acid cycle amplification and nanomaterial amplification strategies to improve the detection sensitivity. Finally, the limitations and challenges in the design of multiplexed aptasensor are also taken into account.

A Calibration Curve Implanted Enzyme-Linked Immunosorbent Assay for Simultaneously Quantitative Determination of Multiplex Mycotoxins in Cereal Samples, Soybean and Peanut

In this study, a rapid and sensitive immunoassay method has been established based on calibration curve implanted enzyme-linked immunosorbent assay (C-ELISA) for the simultaneously quantitative determination of aflatoxin B1, deoxynivalenol and zearalenone in cereal samples, soybean and peanut. The C-ELISA avoids using the standard substances during the detection. The principle of the C-ELISA is to implant the optimized standard curve data into the matched analysis software which can make data processing more convenient and faster. The implanted calibration curve software was programmed with C plus plus. In the new immunoassay system for aflatoxin B1, deoxynivalenol and zearalenone, their linear detection ranges were from 0.03~0.81, 1.00~27.00 and 5.00~135.00 ng/g, respectively. Recovery rates from spiked samples ranged from 85% to 110% with the intra-assay coefficients of variation under 5%. Compared with HPLC method, the new method showed consistence in all the observed contents of the three mycotoxins in real samples. The new method can rapidly and reliably high throughput simultaneously screen for multiplex mycotoxins.

Recent advances on functional nucleic acid-based biosensors for detection of food contaminants

It has seen increasing development of reliable, robust, and flexible biosensors for rapid food-safety analysis in the past few decades. Recently, functional nucleic acid-based biosensors have attracted attention because of their programmability, bottom-up characteristics, and structural switches. However, few systematic reviews devoted to categorizing the potential of DNA nanostructures and devices were found for detecting food contaminants. Hence, the applications of functional nucleic acid-based biosensors were reviewed for analyzing food contaminants, including foodborne pathogen bacteria, biotoxins, heavy metals, and et al. In addition to categorizing the various biosensors, multiple signal readout strategies, such as optical, electrochemical, and mass-based signals were also examined. Finally, the future changes and potential opportunities, as well as practical applications of functional nucleic acid-based biosensors were discussed.

A metal-organic framework/aptamer system as a fluorescent biosensor for determination of aflatoxin B1 in food samples

The demand of simple, sensitive, selective and reliable assay for aflatoxin B1 (AFB1) detection is ubiquitous in food safety, due to its high toxic. Herein, a novel fluorescent aptasensor using metal-organic frameworks (UiO-66-NH₂) and TAMRA label aptamer as sensing platform for AFB1 detection was developed. The TAMRA aptamer adsorbed on the surface of UiO-66-NH₂ via van der Waals force and its fluorescence was quenched for the charge transfer from fluorescence dye TAMRA to metal ions of UiO-66-NH₂. After introducing AFB1 to the system, the TAMRA aptamer binded to AFB1 and formed TAMRA aptamer/AFB1complex, making its conformation change and resulting in fluorescence recovery. Thus, the quantity of AFB1 could be analyzed according to the fluorescence signal change. Under optimize experimental conditions, the assay exhibited high sensitivity toward AFB1 in range of 0-180 ng mL^-1 with low limit of detection of 0.35 ng mL^-1 and good specificity against other toxins. Moreover, the aptamer/metal-organic frameworks sensing platform could be utilized to determine AFB1 content in food samples such as corn, rice and milk. It provided a reasonable method for other mycotoxin detection by changing the sequence of aptamer.

Magneto-controlled aptasensor for simultaneous detection of ochratoxin A and fumonisin B1 using inductively coupled plasma mass spectrometry with multiple metal nanoparticles as element labels

The simultaneous detection of multiple mycotoxins is important for food safety. Here, a magneto-controlled aptasensor for quantitative analysis of ochratoxin A (OTA) and fumonisin B1 (FB1) using inductively coupled plasma mass spectrometry (ICP-MS) with multiple metal nanoparticles as element labels was proposed. Firstly, the OTA aptamer (Apt1) and the FB1 aptamer (Apt2) immobilized on the magnetic beads (MBs) were hybridized with probe DNA1-CdSe quantum dots (pDNA1-QDs) and probe DNA2-Ag nanoparticles (pDNA2-Ag NPs) labels, producing the MBs-Apt1-pDNA1-QDs and MBs-Apt2-pDNA2-Ag NPs conjugates, respectively. Then, the MBs-Apt1-OTA and MBs-Apt2-FB1 conjugates were generated with the addition of targets, resulting the pDNA1-QDs and pDNA2-Ag NPs labels released into the solutions. Finally, the signal intensities of ¹¹¹Cd and ¹⁰⁷Ag were detected by ICP-MS, achieving limits of detection of 0.10 and 0.30 ng mL^-1 for OTA and FB1, respectively. The assay showed high specificity and succeeded in wheat flour. The method provides an ideal model for sensitive analysis of multiple mycotoxins in food samples.

Simultaneous electrochemical determination of ochratoxin A and fumonisin B1 with an aptasensor based on the use of a Y-shaped DNA structure on gold nanorods

A complementary DNA (cDNA) was designed to simultaneously hybridize with the ochratoxin A (OTA) aptamer and the fumonisin B1 (FB1) aptamer to form a unique Y-shaped DNA structure and to achieve simultaneous detection. Gold nanorods (AuNRs) were used to immobilize thionine (Th), thiolated ferrocene (Fc), thiolated OTA aptamer (Apt1), and thiolated FB1 aptamer (Apt2), to form an amplified signal element and a recognition element. The Apt1-AuNRs-Th complex and the Apt2-AuNRs-Fc complex hybridize with cDNA to form a unique Y-DNA structure on a gold electrode. This produces two initial electrochemical signals [with 177 μΑ cm^-2 near -0.2 V, and 3121 μΑ cm^-2 near +0.46 V (vs. Ag/AgCl)] by differential pulse voltammetry. Upon addition of 0.1 ng mL^-1 OTA and 0.1 ng mL^-1 FB1, the aptamers bind the two toxins. This results in the release of Apt1-AuNRs-Th and Apt2-AuNRs-Fc, so the peak currents densities decrease to 115 μΑ cm^-2 and 209 μΑ cm^-2. The assay allows simultaneous determination of OTA and FB1 in the 1.0 pg·mL^-1 to 100 ng·mL^-1 concentration ranges, with LODs of 0.47 and 0.26 pg·mL^-1. The assay is reproducible, stable and specific. It was applied to the determination of OTA and FB1 in spiked beer, with recoveries between 89.0% and 102.0%. Graphical abstractSchematic representation of OTA and FB₁ detection based on Apt₂-AuNRs-Fc/Apt₁-AuNRs-Th/cDNA/AuE. (AuNRs: Gold nanorods; Th: thionine; Fc: ferrocene; SH: thiol; BSA: Bovine serum albumin; cDNA: Complementary DNA; Apt₁: Aptamer1; Apt₂: Aptamer2; OTA: Ochratoxin A; FB₁: Fumonisin B₁).

Dual-target electrochemical aptasensor based on co-reduced molybdenum disulfide and Au NPs (rMoS2-Au) for multiplex detection of mycotoxins

Multiple mycotoxin contamination has posed health risks in the area of food safety. In this study, co-reduced molybdenum disulfide and gold nanoparticles (rMoS₂-Au) were designed and used for the first time as an efficient platform endowing electrochemical electrodes with superior electron transfer rates, large surface areas and strong abilities to firmly couple with large amounts of different aptamers. After further modification with thionine (Thi) and 6-(Ferrocenyl) hexanethiol (FC6S), a platform enabling sensitive, selective and simultaneous determination of two important mycotoxins, zearalenone (ZEN) and fumonisin B1 (FB1), was achieved. The established aptasensor showed excellent linear relationships (R² > 0.99) when ZEN and FB1 concentrations were in the range of 1 × 10^-3-10 ng mL^-1 and 1 × 10^-3-1 × 10² ng mL^-1, respectively. High sensitivity of ZEN and FB1 with a limit of detection as low as 5 × 10^-4 ng mL^-1 was obtained with excellent selectivity and stability. The effectiveness of the aptasensor was verified in real maize samples, and satisfactory recoveries were attained. The established platform could be easily expanded to other aptamer-based multiplex screening protocols in biochemical research and clinical diagnosis.

A novel electrochemical aptasensor for fumonisin B1 determination using DNA and exonuclease-I as signal amplification strategy

In this work, using DNA and exonuclease-I (Exo-I) as signal amplification strategy, a novel and facile electrochemical aptasensor was constructed for fumonisin B₁ (FB₁) detection. The G-rich complementary DNA (cDNA) was immobilized onto the electrode surface. Then, aptamer of FB₁ was hybridized with cDNA to form double-stranded DNA. In the absence of FB₁, double-stranded DNA and G-rich cDNA on the electrode surface promoted effectively methylene blue (MB) enrichment and amplified the initial electrochemical response. In the presence of FB₁, the combination of aptamer and FB₁ led to the release of aptamer from the electrode surface and the expose of 3' end of single-stranded cDNA. When Exo-I was added onto the electrode surface, the single-stranded cDNA was degraded in the 3'-5' direction. The decrease of double-stranded DNA and G-rich cDNA resulted in the less access of MB to the electrode surface, which decreased the electrochemical signal. The experimental conditions including incubation time of FB₁, the amount of Exo-I and incubation time of Exo-I were optimized. Under the optimal conditions, the linear relationship between the change of peak current and the logarithmic concentration of FB₁ was observed in the range of 1.0 × 10^-3-1000 ng mL^-1 with a low limit of detection of 0.15 pg mL^-1. The experimental results showed that the prepared aptasensor had acceptable specificity, reproducibility, repeatability and stability. Therefore, this proposed aptasensor has a potential application in the food safety detection.

Nanosilicon-Based Composites for (Bio)sensing Applications: Current Status, Advantages, and Perspectives

This review highlights the application of different types of nanosilicon (nano-Si) materials and nano-Si-based composites for (bio)sensing applications. Different detection approaches and (bio)functionalization protocols were found for certain types of transducers suitable for the detection of biological compounds and gas molecules. The importance of the immobilization process that is responsible for biosensor performance (biomolecule adsorption, surface properties, surface functionalization, etc.) along with the interaction mechanism between biomolecules and nano-Si are disclosed. Current trends in the fabrication of nano-Si-based composites, basic gas detection mechanisms, and the advantages of nano-Si/metal nanoparticles for surface enhanced Raman spectroscopy (SERS)-based detection are proposed.

Oral Curcumin via Hydrophobic Porous Silicon Carrier: Preparation, Characterization, and Toxicological Evaluation In Vivo

Curcumin has antioxidant, anti-inflammatory, antimicrobial, and anticarcinogenic activities. However, the clinical application of curcumin has been restricted by the poor water solubility and low bioavailability of this molecule. In this work, hydrophobic porous silicon (pSi) particles were prepared by electrochemical etching method and grafted with the different hydrophobic groups on their surfaces. The loading efficiency of curcumin in pSi has been investigated. The properties of pSi particles have been characterized by scanning electron microscopy (SEM) and Fourier transform-infrared spectroscopy (FTIR). The highest loading efficiency of curcumin can be obtained with pSi surface modified with the octadecyl silane group. The release properties of curcumin in hydrophobic pSi have been researched in vitro and in vivo. The curcumin in the hydrophobic pSi surface keeps a high antioxidant bioactivity. The toxicological evaluation of the hydrophobic pSi particles indicates they have a high in vivo biocompatibility within the observed dose ranges. The hydrophobic pSi particles could provide an effective and controlled release delivery carrier for curcumin, which may provide a new tool platform for the further development of curcumin.

Developments in mycotoxin analysis: an update for 2017-2018

This review summarises developments that have been published in the period from mid-2017 to mid-2018 on the analysis of various matrices for mycotoxins. Analytical methods to determine aflatoxins, Alternaria toxins, ergot alkaloids, fumonisins, ochratoxins, patulin, trichothecenes, and zearalenone are covered in individual sections. Advances in sampling strategies are discussed in a dedicated section, as are methods used to analyse botanicals and spices, and newly developed comprehensive liquid chromatographic-mass spectrometric 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 the presented methodologies.

Quantifying Mg2+ Binding to ssDNA Oligomers: A Self-Consistent Field Theory Study at Varying Ionic Strengths and Grafting Densities

The performance of aptamer-based biosensors is crucially impacted by their interactions with physiological metal ions, which can alter their structures and chemical properties. Therefore, elucidating the nature of these interactions carries the utmost importance in the robust design of highly efficient biosensors. We investigated Mg2+ binding to varying sequences of polymers to capture the effects of ionic strength and grafting density on ion binding and molecular reorganization of the polymer layer. The polymers are modeled as ssDNA aptamers using a self-consistent field theory, which accounts for non-covalent ion binding by integrating experimentally-derived binding constants. Our model captures the typical polyelectrolyte behavior of chain collapse with increased ionic strength for the ssDNA chains at low grafting density and exhibits the well-known re-entrant phenomena of stretched chains with increased ionic strength at high grafting density. The binding results suggest that electrostatic attraction between the monomers and Mg2+ plays the dominant role in defining the ion cloud around the ssDNA chains and generates a nearly-uniform ion distribution along the chains containing varying monomer sequences. These findings are in qualitative agreement with recent experimental results for Mg2+ binding to surface-bound ssDNA.

Simultaneous determination of paraquat and atrazine in water samples with a white light reflectance spectroscopy biosensor

An optical immunosensor based on White Light Reflectance Spectroscopy for the simultaneous determination of the herbicides atrazine and paraquat in drinking water samples is demonstrated. The biosensor allows for the label-free real-time monitoring of biomolecular interactions taking place onto a SiO₂/Si chip by transforming the shift in the reflected interference spectrum due to reaction to effective biomolecular layer thickness. Dual-analyte determination is accomplished by functionalizing spatially distinct areas of the chip with protein conjugates of the two herbicides and scanning the surface with an optical reflection probe. A competitive immunoassay format was adopted, followed by reaction with secondary antibodies for signal enhancement. The sensor was highly sensitive with detection limits of 40 and 50 pg/mL for paraquat and atrazine, respectively, and the assay duration was 12 min. Recovery values ranging from 90.0 to 110% were determined for the two pesticides in spiked bottled and tap water samples, demonstrating the sensor accuracy. In addition, the sensor could be regenerated and re-used at least 20 times without significant effect on the assay characteristics. Its excellent analytical performance and short analysis time combined with the small sensor size should be helpful for fast on-site determinations of these analytes.