Direct competitive ELISA enhanced by dynamic light scattering for the ultrasensitive detection of aflatoxin B1 in corn samples

Rapid and sensitive detection of domoic acid in shellfish using a magnetic bead-based competitive ELISA with a high-affinity peptide as a molecular binder

Addressing the critical health concerns posed by domoic acid (DA), a neurotoxic compound produced by toxic marine algae and bioaccumulated in shellfish, necessitates the development of a rapid, precise, and robust detection system. Traditional DA detection methods have stability and sensitivity issues, which hinder effective toxin detection. To overcome these limitations, we developed a novel direct competitive enzyme-linked immunosorbent assay (dc-ELISA) platform that utilizes peptide-immobilized magnetic beads (MGBs/peptide). The affinity peptides identified through phage display and chemically synthesized with biotin labels present an innovative alternative to conventional antibodies for ELISA applications. Streptavidin-modified MGBs were used as the bioreceptor carriers to facilitate magnetic separation and simplify sample preparation, making the MGB/peptide-based dc-ELISA platform an ideal tool for comprehensive monitoring efforts. The developed platform exhibits a detection range of 0.5-10 ng mL-1 and a low limit of detection of 0.29 ng mL-1, offering enhanced sensitivity and cost-effectiveness. Moreover, our developed dc-ELISA demonstrated a high recovery rate when validated with DA-spiked CRM-mussel samples. This method overcomes the limitations of traditional detection techniques and offers a scalable and efficient approach to marine toxin surveillance with improved marine environmental monitoring and public health management.

Ultrasensitive dynamic light scattering immunodetection of alpha-fetoprotein using heptamer-amplified nanoparticle crosslinking aggregation

A novel construction strategy is introduced for an ultrasensitive dynamic light scattering (DLS) immunosensor targeting alpha fetoprotein (AFP). This approach relies on a self-assembled heptamer fusion protein (A1-C4bpα), incorporating the dual functions of multivalent recognition and crosslinking aggregation amplification due to the presence of seven AFP-specific A1 nanobodies on the A1-C4bpα heptamer. Leveraging antibody-functionalized magnetic nanoparticles for target AFP capture and DLS signal output, the proposed heptamer-assisted DLS immunosensor offers high sensitivity, strong specificity, and ease of operation. Under the optimized conditions, the designed DLS immunosensor demonstrates excellent linear detection of AFP in the concentration range 0.06 ng mL-1 to 512 ng mL-1, with a detection limit of 15 pg mL-1. The selectivity, accuracy, precision, practicability, and reliability of this newly developed method were further validated through an assay of AFP levels in spiked and actual human serum samples. This work introduces a novel approach for constructing ultrasensitive DLS immunosensors, easily extendable to the sensitive determination of other targets via simply replacing the nanobody sequence, holding great promise in various applications, particularly in disease diagnosis.

Ratiometric fluorescence and absorbance dual-model immunoassay based on 2,3-diaminophenazine and carbon dots for detecting Aflatoxin B1

In this work, a dual-model immunoassay for detecting Aflatoxin B1 (AFB1) was developed based on 2,3-diaminophenazine (DAP) and carbon dots (CDs). Under the catalysis of horseradish peroxidase (HRP), the o-phthalylenediamine (OPD) was oxidized to DAP which had a yellow color and intense fluorescence. The color changes form colorless to yellow was used to design absorbance model immunoassay. Meanwhile, the absorption spectrum of DAP overlapped with the emission spectrum of CDs which caused the fluorescence of CDs to be quenched. The fluorescence changes of DAP and CDs were used to develop ratiometric fluorescence immunoassay. The dual-model immunoassay showed excellent sensitivity with the limits of detection (LODs) of 0.013 ng/mL for fluorescence mode and 0.062 ng/mL for absorbance mode. Meanwhile, both models exhibited great selectivity for AFB1. Additionally, the recovery rates suggested the proposed dual-model immunoassay had great potential in actual samples detection.

Upconversion nanoparticles-modified aptasensors for highly sensitive mycotoxin detection for food quality and safety

Mycotoxins, highly toxic and carcinogenic secondary metabolites produced by certain fungi, pose significant health risks as they contaminate food and feed products globally. Current mycotoxin detection methods have limitations in real-time detection capabilities. Aptasensors, incorporating aptamers as specific recognition elements, are crucial for mycotoxin detection due to their remarkable sensitivity and selectivity in identifying target mycotoxins. The sensitivity of aptasensors can be improved by using upconversion nanoparticles (UCNPs). UCNPs consist of lanthanide ions in ceramic host, and their ladder-like energy levels at f-orbitals have unique photophysical properties, including converting low-energy photons to high-energy emissions by a series of complex processes and offering sharp, low-noise, and sensitive near-infrared to visible detection strategy to enhance the efficacy of aptasensors for novel mycotoxin detection. This article aims to review recent reports on the scope of the potential of UCNPs in mycotoxin detection, focusing on their integration with aptasensors to give readers clear insight. We briefly describe the upconversion photoluminescence (UCPL) mechanism and relevant energy transfer processes influencing UCNP design and optimization. Furthermore, recent studies and advancements in UCNP-based aptasensors will be reviewed. We then discuss the potential impact of UCNP-modified aptasensors on food safety and present an outlook on future directions and challenges in this field. This review article comprehensively explains the current state-of-the-art UCNP-based aptasensors for mycotoxin detection. It provides insights into potential applications by addressing technical and practical challenges for practical implementation.

Europium nanospheres based ultrasensitive fluorescence immunosensor for aflatoxin B1 determination in feed

In this work, a new competitive immunosensor for aflatoxin B1 (AFB1) detection was developed using europium (Eu) fluorescent nanospheres and magnetic beads. Firstly, Eu nanospheres were synthesized through two steps including carboxylated polystyrene nanospheres and Eu-doped polystyrene nanospheres preparation. Then Eu nanospheres were covalently tagged to anti-AFB1 monoclonal antibody (anti-AFB1 mAb) through an EDC coupling method. Carboxylated Fe3O4 magnetic beads were conjugated to AFB1-BSA through EDC/NHS crosslinking to obtain AFB1-BSA-Fe3O4. In the absence of AFB1, Eu-anti-AFB1 mAb were incubated with AFB1-BSA-Fe3O4 to form Eu-anti-AFB1 mAb-AFB1-BSA-Fe3O4 in PBS buffer. However, in the presence of AFB1, the competitive interaction of AFB1 and AFB1-BSA-Fe3O4 to bind with Eu-anti-AFB1 mAb occurred. With the increasing concentration of AFB1, less Eu-anti-AFB1 mAb-AFB1-BSA-Fe3O4 formed. So the fluorescence intensity of Eu-anti-AFB1 mAb-AFB1-BSA-Fe3O4 was gradually decreased after magnetic separation. The degree of fluorescence decrease was linear with respect to the logarithm of AFB1 concentration in the range of 0.01-2 ng/mL in both buffer solution and feed samples and the detection limit was 0.003 ng/mL. What's more, the immunosensor showed excellent specificity for AFB1 without being interfered by other mycotoxins. In consideration of the excellent performance of this immunosensor, we can speculate that the proposed method could be widely used in detecting food contaminants.

A novel Recjf Exo signal amplification strategy based on bioinformatics-assisted truncated aptamer for efficient fluorescence detection of AFB1

Aflatoxin B1 (AFB1) is a typical mycotoxin that signifacntly endangers public health and economy. In this study, we systematically studied the interaction of aptamers with AFB1 using circular dichroism, molecular dynamics, molecular docking, and fluorescence analysis. The truncated sequence aptamers were screened using molecular docking. We successfully obtained the AFB1 aptamer with higher affinity and its truncated form was enhanced by 5.2-fold compared to the initial AFB1 aptamer. In addition, for rapid detection of AFB1, we designed a fluorescent nano-adaptor sensing platform using RecJf exonuclease signal amplification strategy based on the optimal aptamer. The aptasensor showed satisfactory sensitivity towards AFB1 with a linear detection range of 1-400 ng/mL and a detection limit of 0.57 ng/mL. The aptasensor was successfully applied to the determination of AFB1 in soybean oil and corn oil with recoveries of 91.02 %-106.59 % and 87.39 %-110.61 %, respectively. The successful application of the AFB1 aptasensor, developed through bioinformatics truncation of the aptamer, provides a novel approach to creating a cost-effective, eco-friendly, and rapid aptamer sensing platform.

A Label-Free Aptasensor for Turn-On Fluorescent Detection of Aflatoxin B1 Based on an Aggregation-Induced-Emission-Active Probe and Single-Walled Carbon Nanohorns

The determination of the aflatoxin B1 (AFB1) content has received widespread attention in the context of food safety, which is a global public health issue. Accordingly, a label-free and turn-on fluorescent AFB1 determination method is developed herein with an ss-DNA aptamer as the recognition element, 4, 4-(1E,1E)-2, 2-(anthracene-9, 10-diyl) bis(ethene-2, 1-diyl) bis(N, N, N-trimethylbenzenaminium iodide) (DSAI) as the aggregation-induced emission (AIE) fluorescent probe, and single-walled carbon nanohorns (SWCNHs) as the selective part with a fluorescence quenching effect. In the presence of AFB1, the AFB1-specific aptamer undergoes a structural transformation and switches from being a random helix to a folded structure. DSAI's fluorescence is protected as a result of the resistance of the transformed aptamer adsorbed on the SWCNHs' surface. Because DSAI's fluorescence is not quenchable, the fluorescence intensity is calculated as a function of the AFB1 concentration. By simply mixing DSAI, aptamer, AFB1 samples, and SWCNHs, the method can be carried out in 2 h, with a limit of detection (LOD) of 1.83 ng/mL. It has a high selectivity in the presence of other mycotoxins, and its performance is confirmed in soybean sauce with a known concentration of AFB1. The LOD was 1.92 ng/mL in the soy sauce samples and the recovery ranged from 95 to 106%, implying that the presented aptasensor has great potential for food analysis.

Single-Walled Carbon Nanohorn-Based Fluorescence Energy Resonance Transfer Aptasensor Platform for the Detection of Aflatoxin B1

Aflatoxin B1 (AFB1) is one of the most contaminated fungal toxins worldwide and is prone to cause serious economic losses, food insecurity, and health hazards to humans. The rapid, on-site, and economical method for AFB1 detection is need of the day. In this study, an AFB1 aptamer (AFB1-Apt) sensing platform was established for the detection of AFB1. Fluorescent moiety (FAM)-modified aptamers were used for fluorescence response and quenching, based on the adsorption quenching function of single-walled carbon nanohorns (SWCNHs). Basically, in our constructed sensing platform, the AFB1 specifically binds to AFB1-Apt, making a stable complex. This complex with fluorophore resists to be adsorbed by SWCNHs, thus prevent SWCNHs from quenching of fluorscence, resulting in a fluorescence response. This designed sensing strategy was highly selective with a good linear response in the range of 10-100 ng/mL and a low detection limit of 4.1 ng/mL. The practicality of this sensing strategy was verified by using successful spiking experiments on real samples of soybean oil and comparison with the enzyme-linked immunosorbent assay (ELISA) method.

Recent Advances in Electrochemiluminescence Biosensors for Mycotoxin Assay

Rapid and efficient detection of mycotoxins is of great significance in the field of food safety. In this review, several traditional and commercial detection methods are introduced, such as high-performance liquid chromatography (HPLC), liquid chromatography/mass spectrometry (LC/MS), enzyme-linked immunosorbent assay (ELISA), test strips, etc. Electrochemiluminescence (ECL) biosensors have the advantages of high sensitivity and specificity. The use of ECL biosensors for mycotoxins detection has attracted great attention. According to the recognition mechanisms, ECL biosensors are mainly divided into antibody-based, aptamer-based, and molecular imprinting techniques. In this review, we focus on the recent effects towards the designation of diverse ECL biosensors in mycotoxins assay, mainly including their amplification strategies and working mechanism.

Latest strategies for rapid and point of care detection of mycotoxins in food: A review

Mycotoxins contaminated in agricultural products are often highly carcinogenic and genotoxic to humans. With the streamlining of the food industry chain and the improvement of food safety requirements, the traditional laboratory testing mode is constantly challenged due to the expensive equipment, complex operation steps, and lag in testing results. Therefore, rapid detection methods are urgently needed in the food safety system. This review focuses on the latest strategies that can achieve rapid and on-site testing, with particular attention to the nanomaterials integrated biosensors. To provide researchers with the latest trends and inspiration in the field of rapid detection, we summarize several strategies suitable for point of care testing (POCT) of mycotoxins, including enzyme-linked immunoassay (ELISA), lateral flow assay (LFA), fluorescence, electrochemistry, and colorimetry assay. POCT-based strategies are all developing towards intelligence and portability, especially when combined with smartphones, making it easier to read signals for intuitive access and analysis of test data. Detection performance of the devices has also improved considerably with the integration of biosensors and nanomaterials.

A simple and programmable dual-mode aptasensor for the ultrasensitive detection of multidrug-resistant bacteria

Accurately identifying multidrug-resistant (MDR) bacteria from clinical samples has long been a challenge. Herein, we report a simple and programmable dual-mode aptasensor called DAPT to reliably detect MDR bacteria. The DAPT method comprises two elements, namely the mode of dynamic light scattering (Mode-DLS) for ultrasensitive detection and the mode of fluorescence (Mode-Flu) for reliable quantification as a potent complement. Benefiting from the states of aptamer-modified gold nanoparticles (AptGNPs) sensitively changing from dispersion to aggregation, the proposed Mode-DLS achieved the rapid, specific, and ultrasensitive detection of methicillin-resistant Staphylococcus aureus (MRSA) at the limit of detection (LOD) of 4.63 CFU mL^-1 in a proof-of-concept experiment. Simultaneously, the Mode-Flu ensured the accuracy of the detection, especially at a high concentration of bacteria. Moreover, the feasibility and universality of the DAPT platform was validated with four other superbugs by simply reprogramming the corresponding sequence. Overall, the proposed DAPT method based on a dual-mode aptasensor can provide a universal platform for the rapid and ultrasensitive detection of pathogenic bacteria due to its superior programmability.

M13 bacteriophage as biometric component for orderly assembly of dynamic light scattering immunosensor

The ordered assembly of nanostructure is an effective strategy used to manipulate the hydrodynamic diameter (D_H) of nanoparticles. Herein, a versatile dynamic light scattering (DLS) immunosensing platform is presented to sensitively detect small molecules and biomacromolecules by using the M13 phage as the building module to order the assembly of gold nanoflowers and gold-coated magnetic nanoparticles, respectively. After the directional assembly of M13 phage, the D_H of the probes was significantly increased due to its larger filamentous structure, thus improving the detection sensitivity of the DLS immunosensor. The designed M13 assembled DLS immunosensor with competitive and sandwich formats showed high sensitivities for ochratoxin A and alpha-fetoprotein in real corn and undiluted serum samples, with the detection limits of 1.37 and 57 pg/mL, respectively. These values are approximately 15.8 and 164.9 times lower than those of traditional phage-based enzyme-linked immunosorbent assays. Collectively, this work provides a promising strategy to manipulate the D_H of nanoparticles by highly evolved biomaterials such as engineered M13 phages and opens upon a new direction for developing DLS immunosensors to detect various targets by the fusion expression of special peptide or nanobody on the pIII or pVIII protein of M13 phage.

An ultralow concentration of Al-MOFs for turn-on fluorescence detection of aflatoxin B1 in tea samples

A turn-on fluorescent sensing platform based on an ultralow concentration of Al-metal organic frameworks for the detection of aflatoxin B₁ has been developed for the first time. This fluorescence turn-on sensor exhibits the largest fluorescence enhancement (or quenching) constant value of 179404 M^-1 among all luminescence-based chemical sensors reported till date. Moreover, the sensor afforded a rapid detection of aflatoxin B₁, with a linear response in the concentration range of 0.05-9.61 μM and a low detection limit of 11.67 ppb. Additionally, the fabricated sensor showed good repeatability, reproducibility, stability, and selectivity. Most importantly, the practical application of this sensor has been demonstrated by detecting aflatoxin B₁ in complex tea samples with low relative standard deviation (≤7.72%; n = 3) and satisfactory recoveries. In summary, the proposed method has great potential as a simple, sensitive and selective strategy for monitoring aflatoxin B₁ in food samples.

Low-sample-consumption and ultrasensitive detection of procalcitonin by boronate affinity recognition-enhanced dynamic light scattering biosensor

Accurate determination of procalcitonin (PCT) is highly crucial in bacterial infection diagnosis. Many biosensors previously developed suffer from large sample consumption or lengthy waiting time, which raise difficulties for more vulnerable patients, such as infants, old people, and other critically ill patients. To address this dilemma, we present an innovative boronate affinity recognition (BAR)-enhanced dynamic light scattering (DLS) biosensor to achieve ultrasensitive PCT detection. In this biosensing system, monoclonal antibody-modified magnetic nanoparticles (MNP@mAb) are designed as probes to capture PCT from serum samples and generate DLS signal transduction. Polyvalent phenylboronic acid-labeled bovine serum albumin (BSA@PBA) is used as scaffold to aggregate MNP@mAb and PCT (MNP@mAb-PCT) complex because of the specific interaction of cis-diol-containing PCT with boronic acid ligands on the surface of BSA@PBA. The BAR-enhanced DLS biosensor shows ultrahigh sensitivity to PCT determination due to high binding affinity, with the limit of detection of 0.03 pg/mL. The total detection time of PCT in whole blood or serum is less than 15 min with small sample consumption (about 1 μL) due to the rapid magnetic separation and aggregation of MNP@mAb-PCT triggered by BSA@PBA. In addition, the proposed DLS biosensor exhibits a high specificity for PCT quantitative detection. Therefore, this work provides a promising and versatile strategy for extending DLS biosensor to rapid and ultrasensitive detection of trace PCT for broader patients and more urgent cases.

Highly-selective and sensitive plasmon-enhanced fluorescence sensor of aflatoxins

We demonstrate a novel sensor platform with enhanced sensitivity and selectivity for detecting aflatoxin B1 - a common food toxin in cereals. The approach is based on a molecularly imprinted polymer film that provides selective binding of the aflatoxin B1 and fluorescence signal from the analyte molecule enhanced by the local electric field induced in close proximity to the surface of a silver nanoparticle excited at the localized surface plasmon resonance (LSPR) wavelength. Molecularly imprinted polymers (MIPs) with supramolecular aflatoxin-selective receptor sites and embedded spherical silver nanoparticles (with diameters 30-70 nm, the LSPR band 407 nm) were prepared in the form of a thin polymer film on the surface of a glass slide using in situ polymerization. The detection limit of the sensor for aflatoxin B1 is 0.3 ng mL^-1, which is significantly lower than for a fluorescent sensor without silver nanoparticles. The plasmon-enhanced fluorescence factor is 33, and the linear dynamic range of the sensor is 0.3-25 ng mL^-1.

Detection of aflatoxin B1 with a new label-free fluorescence aptasensor based on PVP-coated single-walled carbon nanohorns and SYBR Gold

This paper describes a novel fluorescence label-free aptasensor to detect aflatoxin B₁ (AFB₁) by utilizing SYBR Gold, aptamer, and single-walled carbon nanohorns (SWCNHs). In the presence of AFB₁, the conformation of AFB₁-specific aptamer went through and the spatial structure of this specific aptamer was transformed accordingly. Due to the resistance of the transformed aptamer when adsorbed on the surface of SWCNHs, the protection of the fluorescence of SYBR Gold was accomplished. Consequently, concentrations of AFB₁ showed a strong association with fluorescence intensity. The detection limit (LOD) of AFB₁ was 1.89 ng/mL, while the linear range was 5-200 ng/mL and fluorescence intensity satisfactorily correlated (R² = 0.9919) with the logarithm of AFB₁ concentration.

Recent Progress in Rapid Determination of Mycotoxins Based on Emerging Biorecognition Molecules: A Review

Mycotoxins are secondary metabolites produced by fungal species, which pose significant risk to humans and livestock. The mycotoxins which are produced from Aspergillus, Penicillium, and Fusarium are considered most important and therefore regulated in food- and feedstuffs. Analyses are predominantly performed by official laboratory methods in centralized labs by expert technicians. There is an urgent demand for new low-cost, easy-to-use, and portable analytical devices for rapid on-site determination. Most significant advances were realized in the field bioanalytical techniques based on molecular recognition. This review aims to discuss recent progress in the generation of native biomolecules and new bioinspired materials towards mycotoxins for the development of reliable bioreceptor-based analytical methods. After brief presentation of basic knowledge regarding characteristics of most important mycotoxins, the generation, benefits, and limitations of present and emerging biorecognition molecules, such as polyclonal (pAb), monoclonal (mAb), recombinant antibodies (rAb), aptamers, short peptides, and molecularly imprinted polymers (MIPs), are discussed. Hereinafter, the use of binders in different areas of application, including sample preparation, microplate- and tube-based assays, lateral flow devices, and biosensors, is highlighted. Special focus, on a global scale, is placed on commercial availability of single receptor molecules, test-kits, and biosensor platforms using multiplexed bead-based suspension assays and planar biochip arrays. Future outlook is given with special emphasis on new challenges, such as increasing use of rAb based on synthetic and naïve antibody libraries to renounce animal immunization, multiple-analyte test-kits and high-throughput multiplexing, and determination of masked mycotoxins, including stereoisomeric degradation products.

A Universal Boronate-Affinity Crosslinking-Amplified Dynamic Light Scattering Immunoassay for Point-of-Care Glycoprotein Detection

Herein, we report a universal boronate-affinity crosslinking-amplified dynamic light scattering (DLS) immunoassay for point-of-care (POC) glycoprotein detection in complex samples. This enhanced DLS immunoassay consists of two elements, i.e., antibody-coated magnetic nanoparticles (MNP@mAb) for target capture and DLS signal transduction, and phenylboronic acid-based boronate-affinity materials as crosslinking amplifiers. Upon the addition of targets, glycoproteins are first captured by MNP@mAb and amplified by target-induced crosslinking stemming from the selective binding between the boronic acid ligand and cis-diol-containing glycoprotein, thereby resulting in a remarkably increased DLS signal in the average nanoparticle size. Benefiting from the multivalent binding and fast boronate-affinity reaction between glycoproteins and crosslinkers, the proposed immunosensing strategy has achieved the ultrasensitive and rapid quantitative assay of glycoproteins at the fM level within 15 min. Overall, this work provides a promising and versatile design strategy for extending the DLS technique to detect glycoproteins even in the field or at POC.

Point-of-care COVID-19 diagnostics powered by lateral flow assay

Since its first discovery in December 2019, the global coronavirus disease 2019 (COVID-19) pandemic caused by the novel coronavirus (SARS-CoV-2) has been posing a serious threat to human life and health. Diagnostic testing is critical for the control and management of the COVID-19 pandemic. In particular, diagnostic testing at the point of care (POC) has been widely accepted as part of the post restriction COVID-19 control strategy. Lateral flow assay (LFA) is a popular POC diagnostic platform that plays an important role in controlling the COVID-19 pandemic in industrialized countries and resource-limited settings. Numerous pioneering studies on the design and development of diverse LFA-based diagnostic technologies for the rapid diagnosis of COVID-19 have been done and reported by researchers. Hundreds of LFA-based diagnostic prototypes have sprung up, some of which have been developed into commercial test kits for the rapid diagnosis of COVID-19. In this review, we summarize the crucial role of rapid diagnostic tests using LFA in targeting SARS-CoV-2-specific RNA, antibodies, antigens, and whole virus. Then, we discuss the design principle and working mechanisms of these available LFA methods, emphasizing their clinical diagnostic efficiency. Ultimately, we elaborate the challenges of current LFA diagnostics for COVID-19 and highlight the need for continuous improvement in rapid diagnostic tests.

Carbon Dots/α-Fe2O3-Fe3O4 nanocomposite: Efficient synthesis and application as a novel electrochemical aptasensor for the ultrasensitive determination of aflatoxin B1

Developing an effective method for the detection of aflatoxin B1 (AFB1) remains an arduous task due to the high toxicity of AFB1 to a health concern. In this study, a sensitive and reliable electrochemical aptasensor based on carbon dots/α-Fe₂O₃-Fe₃O₄ nanocomposite (CDs/α-Fe₂O₃-Fe₃O₄) is constructed for the determination of AFB1. The CDs have good electrical conductivity and large specific surface areas to improve the aptasensor's sensitivity. The α-Fe₂O₃-Fe₃O₄ can not only improve the catalytic performance of the aptasensor but also have magnetism, which can realize the recovery of CDs/α-Fe₂O₃-Fe₃O₄ to avoid material waste and environmental pollution. This electrochemical aptasensor can achieve a good linear (0.001-100.0 nM) and excellent detection limit (0.5 pM) for the determination of AFB1. In addition, the aptasensor was also applied to determine AFB1 in beer, rice, and peanuts, all results were in good agreement with HPLC, indicating that the electrochemical aptasensor has a broad application prospect.

Particle Size Measurement Using Dynamic Light Scattering at Ultra-Low Concentration Accounting for Particle Number Fluctuations

Dynamic light scattering (DLS) is a popular method of particle size measurement, but at ultra-low particle concentrations, the occurrence of number concentration fluctuations limits the use of the technique. Number fluctuations add a non-Gaussian term to the scattered light intensity autocorrelation function (ACF). This leads to an inaccurate particle size distribution (PSD) being recovered if the normal DLS analysis model is used. We propose two methods for inverting the DLS data and recovering the PSDs when number fluctuations are apparent. One is to directly establish the relationship between the non-Gaussian ACF and the PSD by the kernel function reconstruction (KFR) method while including the non-Gaussian term to recover the PSD. The other is to remove the effect of the non-Gaussian term in the ACF by the baseline reset (BR) method. By including the number fluctuation term, the ideal recovered PSD can be obtained from the simulated data, but this will not happen in the experimental measurement data. This is because the measured intensity ACF contains more noise than the simulated ACF at ultra-low concentration. In particular, the baseline noise at the tail of long delay time of ACF overwhelms the number fluctuation term, making it difficult to recover reliable PSD data. Resetting the baseline can effectively remove the digital fluctuation term in ACF, which is also a feasible method to improve PSD recovery under ultra-low concentration. However, increasing noise at ultra-low concentrations can lead to errors in determining an effective baseline. This greatly reduces the accuracy of inversion results. Results from simulated and measured ACF data show that, for both methods, noise on the ACF limits reliable PSD recovery.

Omics in the detection and identification of biosynthetic pathways related to mycotoxin synthesis

Mycotoxins are secondary metabolites that are known to be toxic to humans and animals. On the other hand, some mycotoxins and their analogues possess antioxidant as well as antitumor properties, which could be relevant in the fields of pharmaceutical analysis and food research. Omics techniques are a group of analytical tools applied in the biological sciences in order to study genes (genomics), mRNA (transcriptomics), proteins (proteomics), and metabolites (metabolomics). Omics have become a vital tool in the field of mycotoxins, especially contributing to the identification of biomarkers with potential use for the detection of mycotoxigenic species and the gathering of information about the biosynthetic pathways of mycotoxins in different environments. This approach has provided tools for the development of prevention strategies and control measures for different mycotoxins. Additionally, research has revealed important information about the impact of global warming and climate change on the prevalence of mycotoxin issues in society. In the context of foodomics, the aim is to apply omics techniques in order to ensure food safety. The objective of the present review is to determine the state of the art regarding the development of analytical techniques based on omics in the identification of biosynthetic pathways related to mycotoxin synthesis.

A novel colorimetric biosensor for sensitive detection of aflatoxin mediated by bacterial enzymatic reaction in saffron samples

Aflatoxin is regarded as the potent carcinogenic agent which is secreted from fungi and present in some food products. So far, many detection methods have been developed to determine the trace amounts of aflatoxin in foods. In the present study a colorimetric competitive assay for detection of aflatoxin B1 (AFB1) has been developed based on interaction of gelatin functionalized gold nanoparticles (AuNPs@gelatin) in specific enzymatic reaction. Bacterial supernatant containing gelatinase enzyme were used as the substrate that could digest the coated gelatin on the surface of AuNPs and following in the presence of NaCl medium ingredient resulted to color change of AuNPs colloidal solution from red to purple. It was observed that with addition of aflatoxin to the bacterial supernatant, aflatoxin could interfere in aggregation of AuNPs and inhibited the process which subsequently prevent the expected color change induced by AuNPs aggregation. The supernatant containing AuNPs were investigated to analyze their induced surface plasmon resonance spectra through UV-visible spectroscopy. The absorption values were directly proportional with the applied AFB1 concentration. The experiment conditions including incubation time, AuNPs concentration and pH were investigated. The obtained results showed that through this approach we could detect the AFB1 in a linear range from 10 to 140 pg ml^-1, with detection limit of 4 pg ml^-1. Real sample assay in saffron samples showed recoveries percentage of 92.4%-95.3%. The applied approach proposed simple, cost effective and specific method for detection of AFB1 toxin in food samples.

Recent Advances in Conventional Methods and Electrochemical Aptasensors for Mycotoxin Detection

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

Advances in Colorimetric Strategies for Mycotoxins Detection: Toward Rapid Industrial Monitoring

Mycotoxins contamination is a global public health concern. Therefore, highly sensitive and selective techniques are needed for their on-site monitoring. Several approaches are conceivable for mycotoxins analysis, among which colorimetric methods are the most attractive for commercialization purposes thanks to their visual read-out, easy operation, cost-effectiveness, and rapid response. This review covers the latest achievements in the last five years for the development of colorimetric methods specific to mycotoxins analysis, with a particular emphasis on their potential for large-scale applications in food industries. Gathering all types of (bio)receptors, main colorimetric methods are critically discussed, including enzyme-linked assays, lateral flow-assays, microfluidic devices, and homogenous in-solution strategies. This special focus on colorimetry as a versatile transduction method for mycotoxins analysis is comprehensively reviewed for the first time.