A Dual Signal Ratio Electrochemical Sensor Based on DNA Tetrahedrons and Bimetallic Nanocomposites for AFB1 Analysis.

A fluorescent aptasensor based on the synergy of Au NPs/PDDA/LEG nanocomposite and CDs for aflatoxin B1 detection.

Aflatoxin B1 (AFB1), a potent carcinogen produced by Aspergillus fungi, contaminates foods such as corn and peanuts and thereby introduces a serious food safety risk, as it is known to cause liver damage and cancer. Therefore, developing sensitive and rapid detection methods is crucial for protecting public health. This work presented a highly sensitive aptasensor for AFB1 detection, utilizing a fluorescence quenching and recovery strategy based on a gold nanoparticles/poly (diallyldimethylammonium chloride)/liquid-phase exfoliation of graphene (Au NPs/PDDA/LEG) nanocomposite. The composite sensing platform was constructed by employing PDDA to enhance the dispersion of LEG and prevent the aggregation of Au NPs. Aptamers were immobilized onto the Au NP surface via Au-S bonds. Concurrently, carbon dots (CDs) were conjugated to complementary DNA (cDNA) to form cDNA/CDs. In the absence of AFB1, hybridization between the aptamer and cDNA brought CDs into close proximity with Au NPs, resulting in the quenching of CDs fluorescence due to the proximity to Au NPs. Upon the introduction of AFB1, its specific binding to the aptamer competitively displaced cDNA/CDs. This displacement separated CDs from the Au NPs, leading to the recovery of fluorescence intensity. Demonstrating excellent analytical performance, the sensor offered not only a wide linear detection range (1.0 × 10-2-1.0 × 103 ng mL-1), but also a remarkably low limit of detection (LOD) at 1.05 pg mL-1. Testing with corn and peanut samples yielded high recovery rates of 97.63% to 109.65%, confirming the method's reliability, accuracy, and significant potential for practical food safety monitoring of AFB1.

AND-Logic Gated Electrochemical Sensor for Separate Detection of Aflatoxin B1 and Ochratoxin A via Split-Activator CRISPR/Cas12a

To address the frequent co-occurrence of aflatoxin B1 (AFB1) and ochratoxin A (OTA) in real food matrices, as well as the difficulty of achieving both high-specificity recognition and rapid quantification with existing detection methods, this study developed an AND logic-gated electrochemical sensor based on split-activator CRISPR/Cas12a. The sensor constructed an ordered signaling layer on the electrode interface using a DNA tetrahedron. Through DNAzyme-catalyzed reactions triggered separately by the two targets, two split DNA fragments were generated. Only when both fragments coexisted could they jointly activate the trans-cleavage activity of CRISPR/Cas12a, leading to extensive cleavage of the G-quadruplex sequence supported by the DNA tetrahedron. This cleavage caused the loss of the G-quadruplex/hemin signal-reporting group, resulting in a sharp attenuation of the electrochemical signal. By optimizing the heparin sodium concentration, a one-pot integration of the DNAzyme catalytic cycle and the CRISPR cleavage reaction was successfully achieved. The sensor achieved detection limits of 1.12 pg/mL for AFB1 and 0.26 pg/mL for OTA, which are significantly lower than international regulatory limits. For real corn flour, wheat flour, rice flour, and soybean flour samples, spike recoveries ranged from 90.99% to 107.29%, and the results were highly correlated with those obtained using a commercial enzyme-linked immunosorbent assay method (R2 > 0.996) and high-performance liquid chromatography-tandem mass spectrometry (R2 > 0.998). This work not only provides a new, ultrasensitive, and highly specific tool for copresence reporting of dual mycotoxins, but also offers an innovative paradigm for constructing logic-based biosensors designed for intelligent analysis of complex matrices.

An electrochemical biosensor integrating self-propelled nanocarriers with DNA cascade amplification strategy for ultrasensitive PPIA detection.

Peptidylprolyl isomerase A (PPIA) catalyzes cis-trans isomerization of proline residues, a key process regulating protein folding and signal transduction. Its aberrant secretion is closely associated with tumor metastasis and progression, making it a promising biomarker. However, currently available immunoassays often suffer from insufficient sensitivity for low-abundance PPIA detection. Herein, we present an electrochemical biosensor that integrates self-propelled nanocarriers with DNA cascade amplification strategy for ultrasensitive PPIA detection. The biosensor employs PtNPs@COF particles that catalyze H2O2 decomposition to generate O2. This autonomous propulsion accelerates target binding in homogeneous solution and helps mitigate diffusion-limited binding kinetics. After PPIA binding, the liberated DNAzyme catalytically cleaves the co-immobilized substrate strands, generating numerous triggers for the catalytic hairpin assembly (CHA) reaction. The biosensor achieves a wide linear range from 1 pg/mL to 10 μg/mL with a detection limit of 0.330 pg/mL. It also exhibits excellent specificity and performs reliably in clinical lung adenocarcinoma serum specimens, demonstrating its promising applicability for early diagnosis of this malignancy.

Spatially and potential-resolved anti-interference ECL biosensor for simultaneous detection of ochratoxin A and aflatoxin B1.

The simultaneous detection of multiple targets using electrochemiluminescence (ECL) is often hampered by the interference between lumiphores. To address this challenge, a spatially and potential-resolved ECL biosensor was developed for the detection of ochratoxin A (OTA) and aflatoxin B1 (AFB1). Specially, graphitic carbon nitride @ silicon dioxide composite (C3N4@SiO2) and gadolinium-based metal-organic framework (Gd-MOF) were selected as cathodic and anodic emitters, respectively, and covalently immobilized in separate electrode zones to prevent cross-interference. In addition, tetrahedral DNA (TDN) scaffolds were anchored to both emitters, followed by conjugation with Fc-modified aptamer (for AFB1) and Au NP-modified aptamer (for OTA), creating a dual-functional detection interface. In the presence of targets, in the cathode zone, Fc quenched C3N4@SiO2 ECL, while AFB1 binding reversed this quenching, increasing the signal; in the anode zone, AuNPs enhanced Gd-MOF ECL via surface plasmon resonance (SPR) effect, while OTA binding caused signal reduction through aptamer complex dissociation. Optimized conditions enabled independent detection, with linear ranges of 0.01-120 μg/kg for both toxins (LODs: 1.5 × 10-4 μg/kg for OTA and 1.9 × 10-5 μg/kg for AFB1 at S/N = 3).

Electrochemical aptasensor based on DNA nanoflowers for the sensitive detection of acrylamide.

As a prevalent heat-induced byproduct, acrylamide (AA) is frequently generated during thermal food processing, particularly in baked and fried goods. It is a Group 2A carcinogen produced via the Maillard reaction and exhibits neurotoxicity as well as reproductive and developmental toxicity. In this work, DNA nanoflowers (DNF) with remarkable signal amplification were integrated with methylene blue (MB) to fabricate a novel, high-performance electrochemical signal probe. The high affinity and selective recognition of the aptamer toward AA effectively prevents the signal probe from attaching to the electrode surface, enabling ultrasensitive, quantitative electrochemical detection of AA. Under optimal conditions, the proposed sensor achieved an ultra-low limit of detection of 0.948 pM, with a linear response spanning from 0.005 to 500 nM. Moreover, the sensor exhibited exceptional anti-interference capacity, satisfactory reproducibility, favourable repeatability, and long-term operational stability. Detection of actual samples and quality-control samples confirms the reliability of the sensor, indicating promising applications for AA detection and providing a new approach in this field.

DNAzyme-mediated fluorescence sensor based on covalent organic framework for Pb2+ detection