Aflatoxins screening in non-dairy beverages by Mn-doped ZnS quantum dots – Molecularly imprinted polymer fluorescent probe

A smartphone-enabled visual platform for detecting aflatoxins in peanut oil using colorimetric analysis coupled with magnetic imprinted solid-phase extraction

The study aimed to develop a rapid and sensitive colorimetric platform based on the Emerson reaction to visualize and determine total aflatoxins (AFs) in peanut oil. This method offers the advantage of fast screening for AFs (AFB1, AFB2, AFG1, and AFG2), eliminating the need for specific antibodies. The proposed approach combined colorimetric detection with magnetic dummy imprinted solid-phase extraction and purification, enhancing sensitivity and selectivity. The oxidizer aided the colorless AFs in reacting with 4-aminoantipyrine, producing green condensates. Thus, a dual-mode approach was developed for AFs detection, employing both UV-vis colorimetric and smartphone-based colorimetry. Both methods showed a good linear relationship with the concentration of AFs. Notably, the smartphone-based method demonstrated a detection range of 0.5-57 μg/kg, with a detection limit as low as 0.21 μg/kg. The suggested colorimetric methods present a promising potential for onsite detection and fast screening of AFs in actual samples.

Recent advances in molecularly imprinted polymers (MIPs) for visual recognition and inhibition of α-dicarbonyl compound-mediated Maillard reaction products

α-Dicarbonyl compounds (α-DCs) are important intermediates and precursors of harmful Maillard reaction products (e.g., acrylamide and late glycosylation end-products), and they exist widely in thermoprocessed sugar- or fat-rich foods. α-DCs and their end-products are prone to accumulation in the human body and lead to the development of various chronic diseases. Therefore, detection of α-DCs and their associated hazards in food samples is crucial. This paper reviews the preparation of molecularly imprinted polymers (MIPs) enabling visual intelligent responses and the strategies for recognition and capture of α-DCs and their associated hazards, and provides a comprehensive summary of the development of visual MIPs, including integration strategies and applications with real food samples. The visual signal responses as well as the mechanisms for hazard recognition and capture are highlighted. Current challenges and prospects for visual MIPs with advanced applications in food, agricultural and environmental samples are also discussed. This review will open new horizons regarding visual MIPs for recognition and inhibition of hazards in food safety.

Synthesis of molecularly imprinted polymers based on nitrogen-doped carbon dots for specific detection of chlortetracycline by reversed phase microemulsion method

Among the tetracycline antibiotics, chlortetracycline (CTC) is the most frequently used antibiotic except for tetracycline (TC) for enhancing the ability of the organism to fight bacterial infections. The poor metabolism and degradability of CTC can cause serious health effects. Most studies have focused on the detection and analysis of TC, and research on CTC is relatively scarce. This is because the structures of CTC and TC and oxytetracycline (OTC) are extremely similar, and even indistinguishable. In this study, CTC was used as a template molecule and a molecularly imprinted layer was coated on the surface of highly fluorescent N-CDs using a reversed-phase microemulsion method to form N-CDs@MIPs. It was possible to specifically identify CTC without the influence of TC and OTC, which are extremely similar in structure. By comparing with the non-imprinted polymer (N-CDs@NIPs), it exhibited high sensitivity and selectivity with an imprinting factor of 2.02. And it was used in the determination of CTC in milk with recoveries and relative standard deviations of 96.7%-109.8% and 0.64%-3.27%, respectively, with high accuracy and precision. The specificity of the measurement is excellent compared with other assays, and it is a valid and reliable assay.

A smartphone-assisted paper-based ratio fluorescent probe for the rapid and on-site detection of tetracycline in food samples

Rapid, sensitive and portable analytical methods for on-site detection of tetracycline (TC) in food samples is of critical importance for food safety and public health. In this study, a dual-emission ratio fluorescent probe (Gd0.9@Eu0.1) was prepared and utilized for the detection of tetracycline (TC) by observing the fluorescence color change from blue to red. The detection process exhibits a wide linear range (0-52.0 μM), good selectivity and low detection limit (14 nM). A paper-based probe and a colorimetric card was constructed for the visual detection of TC. Furthermore, a novel and portable detection platform combining smartphone and test strip was exploited for the quantitative and on-site detection of TC in real pork sample. The developed method was validated through intra- (n = 5) and inter-day (n = 2) measurements, as well as comparison with a traditional HPLC method. These statistical result validate the reliability and accuracy of the developed method. This intelligent detection platform represents a promising approach for the rapid, sensitive and visual detection of TC in food samples.

Current Trends in Mycotoxin Detection with Various Types of Biosensors

One of the most important tasks in food safety is to properly manage the investigation of mycotoxin contamination in agricultural products and foods made from them, as well as to prevent its occurrence. Monitoring requires a wide range of analytical methods, from expensive analytical procedures with high-tech instrumentation to significantly cheaper biosensor developments or even single-use assays suitable for on-site monitoring. This review provides a summary of the development directions over approximately a decade and a half, grouped according to the biologically sensitive components used. We provide an overview of the use of antibodies, molecularly imprinted polymers, and aptamers, as well as the diversity of biosensors and their applications within the food industry. We also mention the possibility of determining multiple toxins side by side, which would significantly reduce the time required for the analyses.

Synthesis of fluorescent probe based on molecularly imprinted polymers on nitrogen-doped carbon dots for determination of tobramycin in milk

Tobramycin (TOB) plays a considerable role in combating milk spoilage and preventing disease in dairy cows. However, overuse of TOB can lead to nephrotoxicity, ototoxicity, neuromuscular blockade, and hypersensitivity reactions. Here, nitrogen-doped carbon dots (N-CDs) were prepared with ethylenediamine and citric acid, then molecularly imprinted layers were obtained by imprinting of surface on the N-CDs to prepare Nitrogen-doped carbon dot-based molecularly imprinted polymers (N-CDs@MIPs). The fluorescence emission spectrum of this probe showed a linear enhancement with the TOB concentration in the 1-12 μM. Meanwhile, a detection limit of 99.2 nM was obtained. This probe was not affected by the structural analogs of the TOB and can show high sensitivity and selectivity compared to non-imprinted polymers (N-CDs@NIPs). Therefore, it can be successfully used for the trace analysis of TOB in milk with advantages over other reported techniques such as liquid chromatography coupled with tandem mass spectrometry or various aptamer sensors.

Aflatoxin detection technologies: recent advances and future prospects

Aflatoxins have posed serious threat to food safety and human health. Therefore, it is important to detect aflatoxins in samples rapidly and accurately. In this review, various technologies to detect aflatoxins in food are discussed, including conventional ones such as thin-layer chromatography (TLC), high performance liquid chromatography (HPLC), enzyme linked immunosorbent assay (ELISA), colloidal gold immunochromatographic assay (GICA), radioimmunoassay (RIA), fluorescence spectroscopy (FS), as well as emerging ones (e.g., biosensors, molecular imprinting technology, surface plasmon resonance). Critical challenges of these technologies include high cost, complex processing procedures and long processing time, low stability, low repeatability, low accuracy, poor portability, and so on. Critical discussion is provided on the trade-off relationship between detection speed and detection accuracy, as well as the application scenario and sustainability of different technologies. Especially, the prospect of combining different technologies is discussed. Future research is necessary to develop more convenient, more accurate, faster, and cost-effective technologies to detect aflatoxins.

Study on Molecularly Imprinted Polymers Obtained Sonochemically for the Determination of Aflatoxins in Food

Aflatoxins (AFs) are fungi secondary metabolites produced by the Aspergillus family. These compounds can enter the food chain through food contamination, representing a risk to human health. Commercial immunoaffinity columns are widely used for the extraction and cleanup of AFs from food samples; however, their high cost and large solvent consumption create a need for alternative strategies. In this work, an alternative strategy for producing molecularly imprinted polymers (MIPs) was proposed to extract aflatoxins AFB1, AFB2, AFG1, and AFG2 from complex food samples, using liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS). The MIPs were synthesized via a low-cost and rapid (5 min) sonochemical free-radical polymerization, using 1-hydroxy-2-naphthoic acid as a dummy template. MIPs-based solid phase extraction performance was tested on 17 dietary supplements (vegetables, fruits, and cereals), obtaining appreciable recovery rates (65-90%) and good reproducibility (RSD ≤ 6%, n = 3); the selectivity towards other mycotoxins was proved and the data obtained compared with commercial immunoaffinity columns. The proposed strategy can be considered an alternative affordable approach to the classical immunoaffinity columns, since it is more selective and better performing.

A Critical Review on the Use of Molecular Imprinting for Trace Heavy Metal and Micropollutant Detection

Molecular recognition has been described as the “ultimate” form of sensing and plays a fundamental role in biological processes. There is a move towards biomimetic recognition elements to overcome inherent problems of natural receptors such as limited stability, high-cost, and variation in response. In recent years, several alternatives have emerged which have found their first commercial applications. In this review, we focus on molecularly imprinted polymers (MIPs) since they present an attractive alternative due to recent breakthroughs in polymer science and nanotechnology. For example, innovative solid-phase synthesis methods can produce MIPs with sometimes greater affinities than natural receptors. Although industry and environmental agencies require sensors for continuous monitoring, the regulatory barrier for employing MIP-based sensors is still low for environmental applications. Despite this, there are currently no sensors in this area, which is likely due to low profitability and the need for new legislation to promote the development of MIP-based sensors for pollutant and heavy metal monitoring. The increased demand for point-of-use devices and home testing kits is driving an exponential growth in biosensor production, leading to an expected market value of over GPB 25 billion by 2023. A key requirement of point-of-use devices is portability, since the test must be conducted at “the time and place” to pinpoint sources of contamination in food and/or water samples. Therefore, this review will focus on MIP-based sensors for monitoring pollutants and heavy metals by critically evaluating relevant literature sources from 1993 to 2022.

Progress and challenges in sensing of mycotoxins using molecularly imprinted polymers

Mycotoxin is toxic secondary metabolite formed by certain filamentous fungi. This toxic compound can enter the food chain through contamination of food (e.g., by colonization of toxigenic fungi on food). In light of the growing concerns on the health hazards posed by mycotoxins, it is desirable to develop reliable analytical tools for their detection in food products in both sensitive and efficient manner. For this purpose, the potential utility of molecularly imprinted polymers (MIPs) has been explored due to their meritful properties (e.g., large number of tailor-made binding sites, sensitive template molecules, high recognition specificity, and structure predictability). This review addresses the recent advances in the application of MIPs toward the sensing of various mycotoxins (e.g., aflatoxins and patulin) along with their fabrication strategies. Then, performance evaluation is made for various types of MIP- and non-MIP-based sensing platforms built for the listed target mycotoxins in terms of quality assurance such as limit of detection (LOD). Further, the present challenges in the MIP-based sensing application of mycotoxins are discussed along with the future outlook in this research field.

Three-Dimensional Ordered Macroporous Magnetic Inverse Photonic Crystal Microsphere-Based Molecularly Imprinted Polymer for Selective Capture of Aflatoxin B1

Development of an efficient detection method to monitor residual mycotoxins in food is very important to ensure food safety, but the complex food matrix seriously affects the detection sensitivity and accuracy. Here, using a three-dimensional ordered macroporous magnetic inverse photonic crystal microsphere (MPCM) as the supporting material, a molecularly imprinted polymer (MIP) that can selectively recognize aflatoxin B₁ (AFB₁) was synthesized through the dummy template imprinting strategy. The MPCM@MIP prepared by employing 5,7-dimethoxycoumarin as the template and methacrylic acid as the functional monomer displayed selectivity toward AFB₁ (imprinting factor of 1.5) and could be used as a solid-phase extraction material. By coupling with high-performance liquid chromatography, an analytical method targeting AFB₁ was established and displayed a wide linear range of 5-1000 ng/mL with a low detection limit of 0.4 ng/mL. The method showed a good recovery rate of 73-92% in AFB₁-spiked soy sauce and vinegar samples. Moreover, the MPCM@MIP could be separated from the sample solution easily because of its magnetic performance, displaying a promising future not only in the enrichment of AFB₁ to improve the detection sensitivity and accuracy but also in the removal of AFB₁ from food and environmental samples.

Mycotoxins detection: view in the lens of molecularly imprinted polymer and nanoparticles

Molecularly imprinted polymers (MIPs) are tailor-made functional composites which selectively recognize and bind the target molecule of interest. MIP composites are products of the massively cross-linked polymer matrices, generated via polymerization, with bio-inspired recognition cavities that are morphologically similar in size, shape and spatial patterns to the target conformation. These features have enabled researchers to expand the field of molecular recognition, more specifically for target with peculiar requirements. Nevertheless, MIPs alone are characterized with weak sensitivity. Besides, nanoparticles (NPs) are remarkably sensitive but also suffer from poor selectivity. Intriguingly, the combination of the two results in a highly sensitive and selective MIP composite. For instance, the conjugation of different functional NPs with MIPs can generate new flexible target capture tools, either a dynamic sensor or a novel drug delivery system. In this regard, although the technology is considered an established and feasible approach, it is still perceived as a burgeoning technology for various fields, which makes it unceasingly worthy reviewing. Therefore, in this review, we attempt to give an update on various custom-made biosensors based on MIPs in combination with various NPs for the detection of mycotoxins, the toxic secondary metabolites of fungi. We first summarize the classification, prevalence, and toxicological characteristics of common mycotoxins. Next, we provide an overview of MIP composites and their characterization, and then segment the role of NPs with respect to common types of MIP-based sensors. At last, conclusions and outlook are discussed.

Preparation and properties of aflatoxins imprinted polymer grafted onto the surface of mesoporous silica SBA-15 functionalized with double bonds

Mesoporous silica Santa Barbara-15 was functionalized by methacryloxypropyl trimethoxysilane. Taking this as the carrier material, a new mesoporous silica surface imprinted polymer was synthesized by using the C=C bond, functional monomer α-methacrylic acid, and crosslinker ethylene glycol dimethacrylate, which was used to extract aflatoxin from grain efficiently. It is different from the preparation of surface imprinted polymers which is physically wrapping carrier materials with polymer layers. The chemical grafting method makes the coating of the polymer layer more controllable. A new method for selective separation, enrichment, and determination of trace aflatoxin in grain was established by using the polymers as the filter of the solid-phase extraction column and high-performance liquid chromatography. The linear range of the method was 0.5-100 μg/kg, R²  = 0.9990-0.9993. The recovery of aflatoxin G2, G1, B2, and B1 was 98.9-119.7% and the relative standard deviation was 3.07-5.76%. By comparing the self-made column with the immunoaffinity column, it was found that the self-made column had better extraction performance for aflatoxins than the immunoaffinity column. It can be used for the analysis and detection of aflatoxins in cereal.

Assessment of trace levels of aflatoxins AFB1 and AFB2 in non-dairy beverages by molecularly imprinted polymer based micro solid-phase extraction and liquid chromatography-tandem mass spectrometry

A selective molecularly imprinted polymer (MIP) adsorbent was synthesised and used in a batch micro-solid phase extraction format for isolating aflatoxins (AFB1, and AFB2) from non-dairy beverages before liquid chromatography-tandem mass spectrometry determination. MIP synthesis (precipitation polymerization in 3 : 1 acetonitrile/toluene as a porogen) was performed with 5,7-dimethoxycoumarin (DMC), methacrylic acid (MAA) and divinylbenzene-80 (DVB) as a dummy template, functional monomer and cross-linker, respectively (1 : 4 : 20 molar ratio). 2,2'-Azobisisobutyronitrile (AIBN) was used as a polymerization initiator. The adsorbent MIP (50 mg) was enclosed in a cone-shaped polypropylene membrane (porous membrane protected molecularly imprinted micro-solid phase extraction), and parameters such as sample pH, mechanical (orbital-horizontal) shaking, the extraction time (loading stage), the composition of the eluting solution, and the desorption time were optimised. The highest extraction yields were obtained by using 5 mL of non-dairy beverages (pH adjusted at 6.0), and mechanical shaking (150 rpm) for 15 min. Elution was performed with 5 mL of an acetonitrile/formic acid (97.5 : 2.5) mixture under ultrasound (325 W, 35 kHz) for 15 min. After eluate evaporation to dryness and re-dissolution in 150 μL of the mobile phase, the pre-concentration factor of the method was 33.3, which yields limits of detection within the 0.085-0.207 μg L^-1 range. In addition, the current proposal was shown to be an accurate and precise method through relative standard deviation of intraday and inter-day assays below 18% and analytical recoveries in the range of 91-104%. However, the method was found to suffer from matrix effects.

Quantitative detection of aflatoxin B1 using quantum dots-based immunoassay in a recyclable gravity-driven microfluidic chip

To achieve rapid and sensitive detection of aflatoxin B₁ (AFB₁), we developed a polydimethylsiloxane gravity-driven cyclic microfluidic chip using the two-signal mode strategy. The structural design of the chip, together with the two-wavelength quantum dot ratio fluorescence, effectively eliminates the influence of environmental factors, improves the signal stability, and ensures that the final detection result positively correlates with the target concentration. Moreover, the theoretical analysis performed for the established physical model of the three-dimensional reaction interface inside the chip confirmed the improved reaction rate of immune adsorption in the microfluidic strategy. Overall, the method exhibited a wide analytic range (0.2-500 ng mL^-1), low detection limit (0.06 ng mL^-1), high specificity, good precision (coefficient of variation < 5%), excellent reusability (20 times, 89.1%) and satisfactory practical sample analysis capacity. Furthermore, the reusability and designability of this chip provide a reliable scheme for field detection of AFB₁, analysis of other small molecules, and establishment of high-throughput detection systems under different conditions.

An overview of nanomaterial based biosensors for detection of Aflatoxin B1 toxicity in foods

Aflatoxin B1 (AFB1) is one of the most potent mycotoxin contaminating several foods and feeds. It suppresses immunity and consequently increases mutagenicity, carcinogenicity, teratogenicity, hepatotoxicity, embryonic toxicity and increasing morbidity and mortality. Continuous exposure of AFB1 causes liver damage and thus increases the prevalence of cirrhosis and hepatic cancer. This article was planned to provide understanding of AFB1 toxicity and provides future directions for fabrication of cost effective and user-friendly nanomaterials based analytical devices. In the present article various conventional (chromatographic & spectroscopic), modern (PCR & immunoassays) and nanomaterials based biosensing techniques (electrochemical, optical, piezoelectrical and microfluidic) are discussed alongwith their merits and demerits. Nanomaterials based amperometric biosensors are found to be more stable, selective and cost-effective analytical devices in comparison to other biosensors. But many unresolved issues about their stability, toxicity and metabolic fate needs further studies. In-depth studies are needed for development of advanced nanomaterials integrated biosensors for specific, sensitive and fast monitoring of AFB1 toxicity in foods. Integration of biosensing system with micro array technology for simultaneous and automated detection of multiple AFs in real samples is also needed. Concerted efforts are also required to reduce their possible hazardous consequences of nanomaterials based biosensors.

Molecularly Imprinted Polymer-Quantum Dot Materials in Optical Sensors: An Overview of Their Synthesis and Applications

In the last decades analytical methods have focused on the determination of target analytes at very low concentration levels. This has been accomplished through the use of traditional analytical methods that usually require high reagent consumption, expensive equipment and long pretreatment steps. Thus, there is a demand for simple, rapid, highly selective and user-friendly detection procedures. Quantum dots (QDs) are semiconductor fluorescent nanomaterials with unique optoelectronic properties that have shown great potential for the development of fluorescence probes. Besides, the combination of QDs with molecularly imprinted polymer (MIPs), synthetic materials with selective recognition, have been proposed as useful materials in the development of optical sensors. The resulting MIP-QDs optical sensors integrate the advantages of both techniques: the high sensitivity of QDs-based fluorescence sensors and the high selectivity of MIPs. This review gives a brief overview of the strategies for the synthesis of MIPs-QDs based optical sensors, highlighting the modifications in the synthesis procedure that improve the sensor performance. Finally, a revision of recent applications in sensing and bioimaging is presented.

Novel synthesis of Mn: ZnSe@ZnS core-shell quantum dots based on photoinduced fluorescence enhancement

A novel Type-I Mn: ZnSe@ZnS core-shell quantum dots (QDs) was reported through a two-step procedure by using low-cost inorganic salts and naturalbiomacromolecule as raw materials. Based on a designed structure of L-cysteine-capped Mn: ZnSe QDs in aqueous media with the controllable surface, Mn: ZnSe@ZnS core-shell QDs were formed due to photoactive ions and defect curing under continuous constant light. The influences of experimental variables, including synthesis conditions of Mn: ZnSe QDs, different types and affecting factors of photo irradiation had been systematically investigated. Under the effect of photoinduced fluorescence enhancement, the photoluminescence (PL) intensity increases significantly by about 5-10 times after 1-3 h of UV irradiation. The position of the fluorescence peak was red-shifted by about 17 nm, emitting orange-red fluorescence. The photoluminescence quantum yield (PL QY) was markedly improved (up to 35%). The structure and morphology of Mn: ZnSe@ZnS core-shell QDs were also confirmed by Fourier transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and energy-dispersive X-ray spectroscopy (EDS) in detail. The mechanism of photoinduced fluorescence enhancement was attributed to L-cysteine allowed to release S^2- to form a ZnS shell, and the passivated surface non-radiative relaxation centers of Mn: ZnSe@ZnS QDs was successfully synthesized with highuniform size, excellent photoluminescence performance, and good stability, all ofwhichmakethemgood potential candidates for white LEDs, and biological labels.

A review of the incorporation of QDs and imprinting technology in optical sensors – imprinting methods and sensing responses

This review aims to cover the simultaneous method of using molecularly imprinted technology and quantum dots (QDs) as well as its application in the field of optical sensors.

Application of molecularly imprinted polymers for the separation and detection of aflatoxin

Aflatoxins are extremely harmful carcinogens to humans and animals. In recent years, attention has been directed toward the application of molecular imprinting polymers for the separation and detection of aflatoxin. In this review, polymerization methods for the preparation of molecular imprinting polymers for aflatoxin detection, such as lump-bulk polymerization, spherical molecular imprinting polymer synthesis, surface-imprinted polymerization, and electropolymerization, are described. The applications of molecular imprinting polymers in solid-phase extraction, biosensors, and the surface-enhanced Raman detection of aflatoxin are also reviewed in this paper.

A review on graphene-based electrochemical sensor for mycotoxins detection

This work focuses on the study of nanomaterial-based sensors for mycotoxins detection. Due to their adverse effects on humans and animals, mycotoxins are heavily regulated, and the foodstuff and feed stocks with a high probability of being contaminated are often analyzed. In this context, the recent developments in graphene-based electrochemical sensors for mycotoxins detection were examined. The mycotoxins' toxicity implications on their detection and the development of diverse recognition elements are described considering the current challenges and limitations.

MIPs for commercial application in low-cost sensors and assays - An overview of the current status quo

Molecularly imprinted polymers (MIPs) have emerged over the past few decades as interesting synthetic alternatives due to their long-term chemical and physical stability and low-cost synthesis procedure. They have been integrated into many sensing platforms and assay formats for the detection of various targets, ranging from small molecules to macromolecular entities such as pathogens and whole cells. Despite the advantages MIPs have over natural receptors in terms of commercialization, the striking success stories of biosensor applications such as the glucose meter or the self-test for pregnancy have not been matched by MIP-based sensor or detection kits yet. In this review, we zoom in on the commercial potential of MIP technology and aim to summarize the latest developments in their commercialization and integration into sensors and assays with high commercial potential. We will also analyze which bottlenecks are inflicting with commercialization and how recent advances in commercial MIP synthesis could overcome these obstacles in order for MIPs to truly achieve their commercial potential in the near future.

Smart materials for point-of-care testing: From sample extraction to analyte sensing and readout signal generator

The last decade has seen a surge of technical developments in the field on point-of-care testing (POCT). While these developments are extremely diverse, the common aim is to implement improved methods for quick, reliable and inexpensive diagnosis of patients within the clinical setting. While examples of successful introduction and use of POCT techniques are growing, further developments are still necessary to create POCT devices with better portability, usability and performance. Advances in smart materials emerge as potentially valuable know-hows to provide a competitive edge to the development of next generation POCT devices. This review describes the key advantages of adopting smart material-based technologies at different analytical stages of a POCT platform. Under these analytical stages which involves sample pre-treatment, analyte sensing and readout signal generator, several concepts and approaches from contemporary research work in using smart material-based technologies will be the major focus in this review. Lastly, challenges and potential outlook in implementing materials technologies from the application point of view for POCT will be discussed.

Dual fluorescent immunochromatographic assay for simultaneous quantitative detection of citrinin and zearalenone in corn samples

The presence of multiple mycotoxins in the agricultural products poses a serious threat to the health of humans and animals. Citrinin (CIT) causes slow growth in animals and damages the kidney function. Zearalenone (ZEN) causes chronic poisoning, abnormal functioning and even death in animals. Herein, a dual fluorescent immunochromatographic assay (DF-ICA) based on europium nanoparticles (EuNPs) was developed for the simultaneous detection of CIT and ZEN in the corn samples. After optimization, the limits of detection (LODs), IC₅₀ and average recoveries for the simultaneous determination of CIT and ZEN were 0.06 and 0.11 ng/mL, 0.35 and 0.76 ng/mL, from 86.3% to 111.6% and from 86.6% to 114.4%, respectively. Moreover, the DF-ICA was validated by high performance liquid chromatography (HPLC) analyses, and a satisfactory consistency was obtained. In brief, this work demonstrates the feasibility of DF-ICA for simultaneous monitoring of CIT and ZEN in the corn samples.

The Recent Advances of Fluorescent Sensors Based on Molecularly Imprinted Fluorescent Nanoparticles for Pharmaceutical Analysis

Fluorescent nanoparticles have good chemical stability and photostability, controllable optical properties and larger stokes shift. In light of their designability and functionability, the fluorescent nanoparticles are widely used as the fluorescent probes for diverse applications. To enhance the sensitivity and selectivity, the combination of the fluorescent nanoparticles with the molecularly imprinted polymer, i.e. molecularly imprinted fluorescent nanoparticles (MIFN), was an effective way. The sensor based on MIFN (the MIFN sensor) could be more compatible with the complex sample matrix, which was especially widely adopted in medical and biological analysis. In this mini-review, the construction method, detective mechanism and types of MIFN sensors are elaborated. The current applications of MIFN sensors in pharmaceutical analysis, including pesticides/herbicide, veterinary drugs/drugs residues and human related proteins, are highlighted based on the literature in the recent three years. Finally, the research prospect and development trend of the MIFN sensor are forecasted.

Progress on Structured Biosensors for Monitoring Aflatoxin B1 From Biofilms: A Review

Aspergillus exists commonly in many crops and any process of crop growth, harvest, storage, and processing can be polluted by this fungus. Once it forms a biofilm, Aspergillus can produce many toxins, such as aflatoxin B1 (AFB1), ochratoxin, zearalenone, fumonisin, and patulin. Among these toxins, AFB1 possesses the highest toxicity and is labeled as a group I carcinogen in humans and animals. Consequently, the proper control of AFB1 produced from biofilms in food and feed has long been recognized. Moreover, many biosensors have been applied to monitor AFB1 in biofilms in food. Additionally, in recent years, novel molecular recognition elements and transducer elements have been introduced for the detection of AFB1. This review presents an outline of recent progress made in the development of biosensors capable of determining AFB1 in biofilms, such as aptasensors, immunosensors, and molecularly imprinted polymer (MIP) biosensors. In addition, the current feasibility, shortcomings, and future challenges of AFB1 determination and analysis are addressed.

Alkaline Hydrolysis Behavior of Metal-Organic Frameworks NH2-MIL-53(Al) Employed for Sensitive Immunoassay via Releasing Fluorescent Molecules

Nanosized metal-organic frameworks (MOFs) NH₂-MIL-53(Al) were synthesized from 2-aminoterephthalic acid (NH₂·H₂BDC) and AlCl₃ by a facile hydrothermal method. The synthesized MOFs displayed good stability and a uniform particle size in a netural medium and were hydrolyzed in alkaline medium to release a large amount of fluorescent ligand NH₂·H₂BDC. Therefore, they can act as large-capability nanovehicles to load signal molecules for investigating various biorecognition events. In this work, based on the alkaline hydrolysis behavior of MOFs NH₂-MIL-53(Al), a sensitive immunoassay method was developed for the detection of aflatoxin B₁ (AFB₁) by employing them as fluorescent signal probes. With a competitive immunoassay mode on microplate, AFB₁ can be detected within a linear range of 0.05-25 ng mL^-1. The method was successfully employed to detect AFB₁ spiked in Job tears, Polygala tenuifolia and with acceptable recovery values of 83.00-114.00%. The detection results for moldy Fructus xanthii displayed an acceptable agreement with those from the high-performance liquid chromatography method, with relative errors of -14.21 to 3.49%. With the merits of high sensitivity, facile manipulation, and ideal reliability, the approach can also be extended to other areas such as aptasensor and receptor-binding assay.

Recent advances of molecularly imprinted polymer-based sensors in the detection of food safety hazard factors

With increasing economic globalization, food safety is becoming the most serious concern in the food production and distribution system. Food safety hazard factors (FSHFs) can be categorized into chemical hazards, biological hazards and physical hazards, with the detection of the former two having fascinated interdisciplinary research areas spanning chemistry, material science and biological science. Molecularly imprinted polymer (MIP) -based sensors overcome many limitations of traditional detection methods and provide opportunities for efficient, sensitive and low-cost detection using smart miniaturized equipment. With highly specific molecular recognition capacity and high stability in harsh chemical and physical conditions, MIPs have been used in sensing platforms such as electrochemical, optical and mass-sensitive sensors as promising alternatives to bio-receptors for food analysis. In this systemic review, we summarize recent advances of MIPs and MIP-based sensors, such as popular monomers, usual polymerization strategies, fresh modification materials and advanced sensing mechanisms. The applications of MIP-based sensors in FSHF detection are discussed according to sensing mechanisms, including electrochemistry, optics and mass-sensitivity. Finally, future perspectives and challenges are discussed.