Ultrasensitive Detection Of Aflatoxin B1 Research Articles

MNPs-aptazymes-PtNPs molecular motor biosensor mediated by circular cleavage reactions for the ultrasensitive detection of aflatoxin B1 in real samples

As a significant food safety risk factor linked to cancer, liver diseases, and kidney diseases, aflatoxin B1 (AFB1) necessitates rapid and ultrasensitive detection to mitigate its associated high morbidity and mortality rates. In this study, we developed an advanced biosensor for AFB1 detection by optimizing magnetic nanoparticles (MNPs), platinum nanoparticles (PtNPs), and aptazymes. The resulting MNPs-aptazymes-PtNPs molecular motor biosensor demonstrates promising capabilities for AFB1 detection. Initially, the specific binding between AFB1 and a split aptamer pair facilitates the conversion of intermolecular hybridization of DNAzyme strands into intramolecular hybridization on the MNPs surface. Then the catalytic strands of DNAzyme cleave substrate strands, resulting in PtNPs-containing fragments being released from the MNPs surface and enabling the molecular motor’s movement. The extensive cleavage of substrate strands by the long catalytic strands and the stepwise movement on MNPs surface are driven by the target-specific binding of AFB1. With high peroxidase-mimicking activity, the released PtNPs enable AFB1 detection after short incubation period. The MNPs-aptazymes-PtNPs molecular motor exhibits a sensitivity of 98.95 % and a specificity of 100 %, with a minimum detectable concentration of 300 fg/mL. This thermostabilized, cyclic, and enzyme-free nanomachine demonstrates broad applicability for the detection of various aflatoxins due to its target-empowered, sequence-independent mechanism, possesses excellent guarantee and supervision for enormous Ganoderma products in Shandong province, China.

A comparative study of aptasensor vs. immunosensor for ultrasensitive detection of aflatoxin B1 using Ag-pSi SERS substrate

Numerous SERS based platforms have been designed to address the emerging need for detecting fungal metabolite contamination in foodstuffs, and specifically the Group 1 carcinogen aflatoxin B1. Herein, 4-aminothiophenol modified silver-coated porous silicon was used as the SERS substrate. Two ratiometric responses were individually assessed upon direct target capture using specific aptamers or antibodies. Under optimized physical features, elevated enhancement factor, wide dynamic range, low detection limits and pronounced recycling capabilities were achieved (7.39 × 107, 0.2–200 ppb, 0.0085 and 0.0110 ppb, 7 and 1 regeneration cycles without impairing the performances for aptasensor and immunosensor, respectively). The accuracy and anti-interference responses in several intricate matrices (maize, peanut, wheat, oats and rice) were compared to a routine HPLC method with equivalent recoveries. Overall, the comparative assessment revealed preferable features of reusability, durability and accuracy of the aptasensor over the immunosensor. Furthermore, the results demonstrate the substantial potential of the proposed SERS substrate for diverse on-site analytical applications using simple and portable monitoring instrumentation.

A single-use electrochemical biosensor system for ultrasensitive detection of Aflatoxin B1 in rice, corn, milk, peanut, chili pepper samples

Aflatoxin B1, a common food contaminant in peanuts and corn and a genotoxic carcinogen in humans poses a significant risk for hepatocellular carcinoma, making its detection crucial; this study aims to develop a label-free electrochemical biosensor using a disposable indium tin oxide polyethylene terephthalate (ITO-PET) electrode modified with 3-Aminopropyltriethoxysilane for detecting Aflatoxin B1 in real food samples. Initially, optimization steps for the proposed biosensor were conducted using electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) techniques. Characterization steps such as storage capacity, regeneration, and single frequency impedance (SFI) were completed for the proposed disposable biosensor after the optimization steps. The electrochemical biosensor, based on AFB1, exhibited excellent repeatability and reproducibility. It had a broad dynamic detection range from 0.1 fg/mL to 500 fg/mL, with low limits of detection (LOD) and quantitation (LOQ) at 0.19 fg/mL and 0.65 fg/mL, respectively. Finally, the proposed AFB1-based biosensor system was applied to real food samples (rice, chili pepper, milk, corn, and peanuts) for testing and validation.

Highly conductive AuNPs/Co-MOF nanocomposites synergistic hybridization chain reaction enzyme-free electrochemical aptasensor for ultrasensitive detection of Aflatoxin B1

Aflatoxin B1 (AFB1) is the most poisonous and carcinogenic pollutant among numerous mycotoxins, posing a serious risk to the health of humans. Herein, an electrochemical aptasensor was constructed for AFB1 detection using gold nanoparticles/cobalt-based metal–organic skeleton (AuNPs/Co-MOF) as a modifying material combined with an enzyme-free signal amplification strategy. AuNPs/Co-MOF have an extensive specific surface area and outstanding electrical conductivity, which allows for the loading of a large number of DNA strands and enhancement of the thionine (THi) redox signal, leading to a significant increase in signal response THi loaded bimetallic core–shell nanocomposites (Au@PtNPs) were synthesized as signal labels. Au@PtNPs have high catalytic activity towards THi while improving the efficiency of the loaded THi, which enables the electrochemical signal of THi to be amplified. In addition, the hybridization chain reaction (HCR) signal amplification strategies for enzyme-free amplification elicits a strong response in the electrochemical signal while ensuring sensor stability. The aptasensor has a detection range of 0.001–500 ng/mL and achieves the limit of detection (LOD) was 1.2 × 10-2 pg/mL and limit of quantification (LOQ) was 4.0 × 10-2 pg/mL under optimal experimental conditions. Therefore, applications for electrochemical aptasensors in the realm of food safety monitoring are quite promising.

Multiplex fluorescence quenching immunoassay based on multicolor magnetic quantum dot and dual spectral-overlapped polydopamine nanospheres for ultrasensitive detection of aflatoxin B1, zearalenone, ochratoxin A, and fumonisin B1

Due to the increasing fungal infections and the implementation of strict food safety regulations, the demand for sensitive, rapid, and easy assays for testing co-contaminated mycotoxins in food has grown in recent years. In this study, a multiplex fluorescence quenching immunoassay is developed to simultaneously detect prevalent mycotoxins in cereals, namely aflatoxin B1 (AFB1), zearalenone (ZEN), ochratoxin A (OTA), and fumonisin B1 (FB1). Four spherical nanocomposites with magnetic core and three-layer quantum dot (QD) shell (MagTQD) are fabricated. These nanocomposites exhibit different maximum emission peaks without overlap and interference at the same excitation wavelength. Four MagTQD conjugated with corresponding coating antigens to prepare four fluorescence signal probes with rapid magnetic enrichment ability, respectively. Moreover, polydopamine nanospheres (PDANs) with dual-spectral overlapped fluorescence quenching properties are conjugated with four mycotoxin antibodies to prepare four fluorescence quenching probes, respectively. The established immunoassay has the low detection limit at 1.29 pg mL−1 for AFB1, 0.80 pg mL−1 for ZEN, 1.97 pg mL−1 for OTA, and 13.89 pg mL−1 for FB1, respectively. This developed assay can provide a new approach to realize the efficient detection of multi-mycotoxins in food safety supervision.

DNAzyme-driven tripedal DNA walker for ratiometric electrochemical aptasensor ultrasensitive detection of aflatoxin B1

Aflatoxin B1 is a potent carcinogen widely found in agricultural products and feed. Therefore, investigating the development of convenient, sensitive, and precise techniques for detecting AFB1 is critical. This work proposes a ratiometric electrochemical aptasensor based on DNAzyme-driven tripedal DNA walker for enzyme-free AFB1 detection. The design of multiple legs reduces the moving time on the electrode surface and enhances the value of signal response. In this approach, the tagging of ferrocene and methylene blue as signal switch molecules diminishes the impact of interferences and significantly enhances the reproducibility (RSD: 2.825%). Meanwhile, the tripedal DNA walker and DNAzyme dual signal amplification enabled the sensor to detect AFB1 traces in cereals. We achieved trace detection of AFB1 with a detection limit of 61 fg/mL and a wide linear range from 0.0001 to 10 ng/mL. Furthermore, the aptasensor success rate was comparable to that of HPLC-PMP. The results demonstrate enormous potential for detection. Furthermore, the method can detect various targets by altering the target aptamer, displaying attractive scalability. This suggests its tremendous prospective in detecting mycotoxins in food in the future.

A dual-signal ratiometric electrochemical aptasensor based on Thi/Au/ZIF-8 and catalytic hairpin assembly for ultra-sensitive detection of aflatoxin B1.

Adual-signal ratiometric electrochemical aptasensor has been developed for AFB1 detection using thionine/Au/zeolitic imidazolate framework-8 (Thi/Au/ZIF-8) nanomaterials and catalytic hairpin assembly (CHA) reaction. Thi/Au/ZIF-8 combined with DNA hairpin 2 (H2) was used as a signal probe. [Fe(CN)6]3-/4- was served as another signal probe, and the IThi/Au/ZIF-8/I[Fe(CN)6]3-/4- ratio was for the first timeutilized to quantify AFB1. AFB1-induced CHA was used to expand the ratio of electrical signals. In the presence of AFB1, H2/Thi/Au/ZIF-8 bound to the electrode via CHA, enhanced the current signal of Thi/Au/ZIF-8. H2 contained the DNA phosphate backbone hindered [Fe(CN)6]3-/4- redox reaction and resulted in a lower [Fe(CN)6]3-/4- current signal. This aptasensor exhibited high specificity for AFB1, a linear range of 0.1pgmL-1 to 100ngmL-1, and a detection limit of 0.089pgmL-1. It demonstrated favorable sensitivity, selectivity, stability, and repeatability. The aptasensor was suitable for detecting AFB1 in peanuts and black tea and holds potential for real sample applications.

A dual-signal aptasensor based on cascade amplification for ultrasensitive detection of aflatoxin B1

Aflatoxin B1 (AFB1) is considered as a serious carcinogenic mycotoxin that was widely detected in grains and foods, and its sensitive analysis is of key importance to avoid the health threats for consumers. In this study, a dual-signal aptasensor based on cascade of entropy-driven strand displacement reaction (ESDR) and linear rolling circle amplification (LRCA) was fabricated for ultrasensitive determination of AFB1. At the sensing system, the complementary strand would be released after the aptamer combined with AFB1, which will bring about the functional domains exposed, triggering the subsequent ESDR. Meanwhile, the two strands that were outputted by ESDR would incur the downstream LRCA reaction to produce a pair of long strands to assist in the generation of fluorescence and absorbance signals. Under the optimized conditions, the proposed aptasensor could achieve excellent sensitivity (limit of detection, 0.427 pg/mL) with satisfactory accuracy (recoveries, 92.8–107.9 %; RSD, 2.4–5.0 %), mainly ascribed to the cascade amplification. Importantly, owing to the flexibility design of nucleic acid primer, this analytical method can be applied in monitoring various hazardous substances according to the specific requirements. Our strategy provides some novel insights at signal amplification for rapid detection of AFB1 and other targets.

Polydopamine-coated HKUST MOFs-based strip lateral flow immunoassay for on-site ultrasensitive detection of aflatoxin B1 in foods

Owing to the high residue in foods and severe carcinogenic and teratogenic effects to human health of aflatoxin B1 (AFB1), it is vital to develop a reliable method for sensitive detection of AFB1. In this work, the polydopamine-coated Cu-based metal-organic framework ([email protected]) as a signal amplification marker was introduced to develop a strip lateral flow immunoassay (SLFIA) for on-site detection of AFB1 in food samples. The [email protected] was prepared by simple oxidative self-polymerization of dopamine on the surface of the HKUST. [email protected] with excellent hydrophilicity and biocompatibility allowed rapid labeling of anti-AFB1 monoclonal antibodies (mAbs) by simple physical adsorption. Under optimal conditions, [email protected] probes-based SLFIA could realize the qualitative visualization and sensitive quantitative detection by using a portable test strip reader. The detection limit for AFB1 was as low as 0.01 ng/mL with a wide concentration range of 0.05–2 ng/mL. Practical application in Maize and Lotus seed samples indicated satisfactory recoveries of 80.3–104.6%. The effectiveness and accuracy of the new SLFIA method were verified with a validated UFLC-MS/MS technique. The preparation process of [email protected] SLFIA was easy to operate with significantly improved sensitivity and stability, and could be widely used in the rapid and accurate detection of mycotoxins and other toxic hazards in foods.

Dual-mode electrochemical/colorimetric microfluidic sensor integrated tetrahedral DNA nanostructures with Au/Ni-Co LDH NCs nanozyme for ultrasensitive detection of aflatoxin B1

Aflatoxin B1 (AFB1) is one of the most hazardous mycotoxins and lead to a deadly danger to animal and human health. The development of portable, low-cost, and easy to operate analytical tools is essential for AFB1 detection, especially in resource-limited regions. Herein, a dual-mode microfluidic paper-based analytical device (μPAD) with electrochemical and colorimetric readout was constructed for AFB1 detection using Au NPs anchored Ni-Co layered double hydroxides nanocages (Au/Ni-Co LDH NCs) as a signal amplifier. In this design, tetrahedral DNA nanostructures (TDNs) were employed as a scaffold to anchor “bottom-up” aptamers (Apt) for improving capture efficiency of AFB1. Au/Ni-Co LDH NCs with excellent peroxidase (POD)-like activity were bound on the TDNs through hybridization of Apt and complementary DNA (cDNA), a significant electrochemical signal of H2O2 reduction was generated. Meanwhile, the·OH from H2O2 decomposition catalyzed the oxidation of 3,3′,5,5′-tetramethylbenzidine and resulted in a colorimetric signal. The binding of target AFB1 to Apt triggered the dissociation of Apt/cDNA, causing the release of the signal amplifier from the sensing interface and signal decrease. Consequently, a detection range of 0.2 pg/mL-100 ng/mL for electrochemical and 50 pg/mL-100 ng/mL for colorimetric were achieved for AFB1, holding promising application in the fields of food safety.

Spatial Confinement-Enhanced electrochemiluminescence of Gold nanoclusters in chitosan nanogels and its application for ultrasensitive detection of Aflatoxin B1

Gold nanoclusters (AuNCs), as a category of promising electrochemiluminescence (ECL) emitter, hold great potential for sensing applications. However, its application is still restricted by the relatively low ECL quantum yield and difficult to purification. In this work, AuNCs were confined in a soft chitosan (CS) nanogel matrix (AuNCs@CS) with good biocompatibility via a facile one-pot approach. The as-fabricated AuNCs@CS nanogels showed 2.4-fold ECL intensity relative to that of bare AuNCs without chitosan. The ECL enhancement was attributed to the increased percentage of Au(0) in AuNCs@CS nanogels, the confinement effect of chitosan nanogels, as well as chitosan as a polymer could reduce the diffusion of the radicals and prolong the excited state lifetime of AuNCs in ECL reaction. Moreover, the obtained AuNCs@CS nanogels are stable and easy to be purified by centrifugation. On this basis, a label-free ECL immunosensor for ultrasensitive detection of aflatoxin B1 (AFB1) was developed by using AuNCs@CS nanogels modified fluorine doped tin oxide (FTO) electrode as a sensing interface. The linear range of the proposed immunosensor for AFB1 detection was 3.16 × 10-14 to 3.16 × 10-12 g/mL with a detection limit of 9.3 × 10-15 g/mL, which was at least one order of magnitude lower than the reported ECL biosensor of AFB1. The proposed strategy may be used for the determination of other toxins in the Aflatoxin family if corresponding antibodies are available, which is of great significance for the quality control of Chinese herbal medicine and food safety.

An “off-on” electrochemical luminescence biosensor with aggregation-induced emission for ultrasensitive detection of aflatoxin B1

This work describes a novel “off-on” biosensor for super-sensitive and selective detection of aflatoxin B1 (AFB1). In the biosensor, electrochemiluminescence (ECL) and aggregation-induced emission (AIE) work together to enhance ECL performance by a dibenzo-[b,d]thiophene sulfone-based conjugated microporous polymer, and hairpin DNA1 (H1) and ferrocene (Fc)-apt act as the switches for the "off-on" mode. In the absence of target AFB1, the ECL signal is inhibited because of the steric-hindrance effect, and the biosensor remains in the “off” state. In the presence of AFB1, ECL signal recovery is observed caused by the specific recognition between the AFB1 and Fc-apt, i.e., the biosensor changes to the “on” state. Under optimal experimental conditions, AFB1 can be quantified from 1 pg·mL−1 to 1 μg·mL−1 with an ultralow detection limit of 0.46 pg·mL−1 by the “off-on” biosensor. The biosensor exhibited good practicability for AFB1 assay in corn samples, thus providing a simple and sensitive method for monitoring food safety.

Dual II-scheme nanosheet-like Bi2S3/Bi2O3/Ag2S heterostructures for ultrasensitive PEC aptasensing of aflatoxin B1 coupled with catalytic signal amplification by dendritic nanorod-like Au@Pd@Pt nanozyme

As one of the most toxic chemical substances, aflatoxin B1 (AFB1) has a strong carcinogenic effect even at a trace level in human and animal, which severely threatens human health and even causes cancers. Therefore, ultrasensitive detection of AFB1 is of significant importance. For such analysis, dual II-scheme sheet-like Bi2S3/Bi2O3/Ag2S heterostructures were prepared by the in-situ growth method, which exhibited high separation efficiency for the electron-hole (e−-h+) pairs, prominent stability, and high photoactivity. Moreover, the dendritic nanorod-like Au@Pd@Pt (Au@Pd@Pt DNRs) nanozyme was homely synthesized, whose peroxidase-like activity was scrupulously investigated by catalytical oxidation of diaminobenzidine (DAB) in the presence of H2O2. Integration by the aptasensing strategy, a photoelectrochemical (PEC) “signal-on” aptasensor was prepared, which exhibited a broader linear range of 0.5 pg mL−1–100 ng mL−1 with a lower limit of detection (LOD = 0.09 pg mL−1, S/N = 3). This work provides a feasible strategy to develop advanced PEC biosensors for actual analysis of environmental pollutants.

DNA tetrahedral scaffold-corbelled 3D DNAzyme walker for electrochemiluminescent aflatoxin B1 detection

The reaction efficiency of surface-based DNA walker can directly affect the properties of a biosensor. Herein, three-dimensional (3D) DNAzyme walker were first fixed on the top of DNA tetrahedral scaffold to improve the immobilization efficiency. Ferrocene (Fc) that labeled at substrate strand ends effectively quenched the electrochemiluminescence (ECL) signal of Ru(bpy)2(cpaphen)2+, yielding the sensor in a “signal-off” state. Upon the addition of aflatoxin B1 (AFB1), 3D DNAzyme walker was activated and fueled by Na+, accordingly releasing Fc and recovering the ECL signal of Ru(bpy)2(cpaphen)2+. Due to the high movement efficiency of such 3D DNAzyme walker, ultrasensitive detection of AFB1 was achieved in the range of 1.0 fg mL−1–10 ng mL−1, with a detection limit of 0.58 fg mL−1. Moreover, satisfactory results were obtained while detecting AFB1 in corn and peanut samples, suggesting it has a potential application in food safety analysis.

An ultrasensitive lateral flow immunoassay platform for foodborne biotoxins and pathogenic bacteria based on carbon-dots embedded mesoporous silicon nanoparticles fluorescent reporter probes

Lateral flow immunoassays (LFIAs) are routine methods for rapid foodborne pollutants screening, with detection limits that are closely associated with the label probes used. The exploitation of high performance and robust probe is highly desirable, and remains a great challenge. Herein, we reported an emerging fluorescent nanobeads i.e. carbon-dots (CD) covalently incorporated mesoporous silicon nanoparticles (CD-MSNs) for LFIAs. CD-MSNs revealed brighter fluorescence, larger particle size and more modification sites in comparison with those of single CD. After bio-functionalisation, CD-MSNs probes were introduced to construct LFIA test strips, and designed for ultrasensitive detection of aflatoxin B1 (AFB1) and Staphylococcus aureus (S. aureus), two representative foodborne pollutants, based on the competitive and sandwich models, respectively. Very competitive quantitative detection limits i.e. 0.05 ng/mL and 102 cfu/mL were correspondingly obtained. Additionally, the test strips were successfully applied to rapidly and accurately screen AFB1 and S. aureus in food samples, highlighting their practicality.

High affinity aptamers for ultra-sensitive detection of aflatoxin B1 in milk and groundnut samples with label-free photo-electrochemical aptasensor

Aflatoxin B1 is a potent liver toxin and easily accumulated in foodstuff and environment via the food chain, subjecting high hazards to human health. Rapid initial diagnosis is one of the most impressive monitoring procedures to overcome the potential hazards. Nevertheless, the classical approaches confront many limitations, like low specificity and sensitivity and complicated procedures. Herein, a photo-electrochemical aptasensor based on sensitized poly(dopamine)@functionalized multiwall carbon nanotube/titanium dioxide (PDA@f-MWCNTs/TiO2 NTs) was designed to detect aflatoxin B1 in real samples (e.g. groundnut and milk). The mentioned label-free biosensing platform not only needed simple operations but also presented outstanding reusability, storage stability, reproducibility, and specificity simultaneously. This suggested strategy could sensitively and selectively detect aflatoxin B1 with dynamic range of 0.005–50 ng/mL and a low limit of detection 1 pg/mL. This procedure could provide the bright prospect for detection of aflatoxin B1 residues in foodstuff.

Self-enhanced electrochemiluminescence of luminol induced by palladium–graphene oxide for ultrasensitive detection of aflatoxin B1 in food samples

In this work, a novel and credible electrochemiluminescence immunoassay (ECLIA) was constructed for the ultrasensitive and highly selective detection of aflatoxin B1 (AFB1). Amino-functionalized 3D graphene hydrogel (NGH) served as the ECL platform with the self-enhanced ECL of luminol–palladium–graphene oxide (lum–Pd–GO) acting as a marker for the antibodies against AFB1. Pd–GO was synthesized by a self-redox method; it promotes the formation of reactive oxygen species, which are important to the ECL of luminol, from dissolved oxygen. The π–π conjunction between luminol and GO shortens their electron transfer distance, resulting in an amplified ECL signal (∼8.5 times larger than conventional luminol ECL). Moreover, 3D NGH, with its good conductivity, large surface area, and sufficient amino groups, was used to anchor gold nanoparticles (AuNPs), which subsequently immobilized bovine serum albumin (BSA)–AFB1 through Au–S bonds. The resultant, competitive ECLIA gave a relative low detection limit of 5 × 10−3 μg kg−1 and exhibited a broad linear relationship over the range of 0.05–50 μg kg−1. Finally, the proposed ECLIA was successfully used to analyze AFB1 contents in food samples. ECLIA: electrochemiluminescence immunoassay; AFs: Aflatoxins; HPLC: high-performance liquid chromatography.

A ratiometric electrochemiluminescent/electrochemical strategy based on novel designed BPYHBF nanorod and Fc-MOF with tungsten for ultrasensitive AFB1 detection

Fluorescent dyes have been considered as one of the most potential candidates for electrochemiluminescence (ECL) reagent due to the excellent photophysical and electrochemical characteristics in recent years. However, the severe self-absorption effect caused by narrow stokes shift inevitably limits its application for ECL. In this work, a new type of ECL emitter, 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene derivative, a BF2 complex of hydrazine-schiff base linked bispyrrole, namely BPYHBF, was prepared and employed as a probe to label the competitor of target in the immunosensor, which could emit powerful ECL signal with tri-n-propylamine. The structure and ECL property of BPYHBF were investigated. Additionally, multi-walled carbon nanotube/ferrocenecarboxaldehyde-metal organic framework (MWCNTs/Fc-MOF) as sensing substrate for Ab1 incubation was synthesized, where the large specific surface area and stable internal reference electrochemical signals improved the sensitivity and reliability of the sensor by self-correction. Herein, a novel ratiometric competitive immunosensor based on the ECLBPYHBF/DPVFc was prepared for ultrasensitive detection of aflatoxin B1 (AFB1). The ratio value is linear in the range from 10 fg/mL to 100 ng/mL, and the detection limit is 5.39 fg/mL. The prepared sensor exhibited excellent sensitivity, accuracy and reproducibility, and achieved satisfactory detection towards AFB1 in actual samples, this demonstrates a promising application in biomolecules detection.

A Novel Colorimetric Nano Aptasensor for Ultrasensitive Detection of Aflatoxin B1 Based on the Exonuclease III-Assisted Signal Amplification Approach.

The detection of aflatoxin B1 (AFB1) has recently garnered much attention on the issue of food safety. In this study, a novel and sensitive aptasensor towards AFB1 is proposed using an Exonuclease III (Exo III)-integrated signal amplification strategy. This reported sensing strategy is regulated by aptamer-functionalized nanobeads that can target AFB1; furthermore, complementary DNA (cDNA) strands can lock the immobilized aptamer strands, preventing the signal amplification function of Exo III in the absence of AFB1. The presence of AFB1 triggers the displacement of cDNA, which will then activate the Exo III-integrated signal amplification procedure, resulting in the generation of a guanine (G)-rich sequence to form a G-4/hemin DNAzyme, which can catalyze the substrate of ABTS to produce a green color. Using this method, a practical detection limit of 0.0032 ng/mL and a dynamic range of detection from 0.0032 to 50 ng/mL were obtained. Additionally, the practical application of the established sensing method for AFB1 in complex matrices was demonstrated through recovery experiments. The recovery rate and relative standard deviations (RSD) in three kinds of cereal samples ranged from 93.83% to 111.58%, and 0.82% to 7.20%, respectively, which were comparable with or better than previously reported methods.

Horseradish peroxidase-catalyzed formation of polydopamine for ultra-sensitive magnetic relaxation sensing of aflatoxin B1

Aflatoxin B1 as one of the most toxic mycotoxins poses a major health risk to humans and animals. Highly sensitive detection methods of aflatoxin B1 are urgently required because of its low abundance in biological samples. In this work, we developed a magnetic relaxation sensing strategy using enzyme-catalyzed formation of polydopamine for signal amplification. Horseradish peroxidase can catalyze the reaction to generate polydopamine that assembles magnetic nanoparticles for magnetic relaxation sensing with a high signal-to-noise ratio. Combined with the specific antigen-antibody interaction, this magnetic sensor enables fast and ultra-sensitive detection of aflatoxin B1 by using transverse relaxation time (T2) as a readout. Under optimized conditions, the linear range of this magnetic sensor for detecting aflatoxin B1 is from 10 pg/mL to 10 ng/mL, and the limit of detection is 0.35 pg/mL. This sensor has been challenged for the quantitative analysis of aflatoxin B1 in animal feed samples that is promising for real-world applications.