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Atrazine (ATZ) represents an endocrine-disrupting pesticide posing significant threats to both the environment and human well-being. In this study, a novel turn-on electrochemical aptasensor was successfully developed for highly sensitive ATZ detection. It relied on Ni 6 MnO 8 @C/Au nanorods (Ni 6 MnO 8 @C/AuNR) and covalent-metal organic framework nanohybrids (MCA@Ce-MOF) with RecJ f -catalyzed target recycling amplification. Notably, this marks the first instance of utilizing this strategy for ATZ detection. The substrate material, ultrathin Ni 6 MnO 8 @C/AuNR nanosheets, enhanced the specific surface area, conductivity, and biocompatibility, thereby facilitating biomolecule attachment and improving sensitivity. The scaffolds, hierarchically porous MCA@Ce-MOF, not only elevated the loading efficiency and surface concentration of signal molecules, but also strengthened the binding firmness of biomolecules. RecJ f -catalyzed target recycling was triggered in the presence of ATZ, further magnifying electrochemical signals. Leveraging these unique attributes, the developed aptasensor exhibited exceptional ATZ detection performance with a low detection limit of 4.9 fg·mL−1, a wide linear range of 4 × 10−5–4 ng·mL−1, and a satisfactory recovery of 93.3–99.6% in corn samples. With its diverse signal amplification capabilities, this aptasensor holds promise for detecting various analytes in environmental monitoring applications. • Ni 6 MnO 8 @C/AuNR improved the specific surface area, conductivity, and biocompatibility of the electrode. • MCA@Ce-MOF loaded massive signal molecules and biomolecules. • RecJ f -catalyzed target recycling further amplified the signals. • Achieved highly sensitive detection of ATZ with a detection limit of 4.9 fg·mL1. • This developed aptasensor was successfully applied to detect ATZ in the corn samples. [ABSTRACT FROM AUTHOR]

In this study, a hierarchically porous Zr‐MOF‐labeled electrochemical biosensor for the detection of Adenosine Triphosphate (ATP) was constructed using polyethylenimine‐reduced graphene oxide/Gold nanowire nanocomposite (PEI‐rGO/AuNWs) and exonuclease I (Exo I) assisted target recycling strategy. PEI‐rGO/AuNWs nanocomposite not only favor the immobilization of c‐DNA but also facilitate the electron transfer and elevate the electrode surface area. In addition, hierarchically porous Zr‐MOFs (HP‐UiO‐66), high stability and large mesoporous property, could load more signal molecules. In the presence of ATP, ATP aptamer was released from the c‐DNA, thus introducing MB@Zr‐MOF‐s‐DNA onto the electrode surface. Meanwhile, Exo I selectively digested the aptamer which bound with ATP, the released ATP participated new binding with the rest aptamer. Therefore, a significant increase in MB current intensity was observed. Under optimal conditions, the proposed aptasensor showed excellent performance with a linear range from 10−6 μM to 10 μM and a detection limit of 3.76×10−8 μM by differential pulse voltammetry. In addition, the proposed biosensor showed an outstanding performance with reproducibility, stability and anti‐interference ability, and was applied to the determination of ATP in real samples. [ABSTRACT FROM AUTHOR]

Tobramycin (TOB), an essential aminoglycoside antibiotic in human life, poses potential threats due to its residues in the environment. The primary concern is the adverse impact of excessive TOB on human kidneys, hearing, and other organs, significantly affecting human health. Constructing a sensitive electrochemical platform for simple and rapid trace detection is crucial. Herein, to enhance the sensitivity of TOB detection in the environment and mitigate the risks associated with residual antibiotics, an ultrasensitive electrochemical aptasensor was developed. The sensor employs a dual-cycle amplification strategy involving catalytic hairpin assembly (CHA) and exonuclease III (Exo III) for efficient signal amplification. Simultaneously, the electrode performance was optimized by incorporating gold nanowires (AuNWs) onto the surface of reduced graphene oxide (PDA-rGO). Specifically, in the presence of TOB, which binds to the aptamer (Apt), dsDNA dissociates, releasing cDNA to open hairpin 1 (HP1) and initiate the CHA cycle with the participation of hairpin 2 (HP2). Exo III shears HP1 in the HP1/HP2 complex, freeing HP2 to participate in the CHA cycle again. Ultimately, a significant amount of signal label is retained on the electrode by hybridizing with sheared HP1, generating a robust electrical signal. Through the signal amplification strategy, the aptasensor design provides a broad linear range of 0.005–500 nM, with a low detection limit of 0.112 pM for TOB. It is worth mentioning that the aptasensor displayed favorable stability, specificity, and reproducibility, and has been successfully applied to practical samples, demonstrating its utility in practical applications. [Display omitted] • The utilization of a cascade amplification strategy involving CHA and Exo III enables efficient signal amplification. • AuNWs/PDA-rGO composites were designed as substrate materials to optimize the electrodes. • The sensor demonstrates a low detection limit of 0.112 pM for TOB and possesses a broad linear range. • The developed sensor facilitates highly sensitive and selective detection of TOB in real samples. [ABSTRACT FROM AUTHOR]

A "signal off" electrochemical aptasensor based on metal-organic framework (MOF) - based nanocomposites and RecJf exonuclease-assisted target recycling was constructed for ultrasensitive detection of vanillin (VAN). In this work, benefited from the high catalytic activity of the synthesized gold nanoparticle/iron-based MOF/polyetherimide-reduced graphene oxide (AuNPs/NH 2 -MOF-235(Fe)/PEI-rGO) and the AuNPs/Ce-MOF nanocomposites toward thionine (Thi), the electrochemical signal was amplified. And the target recycling assisted by RecJf exonuclease were triggered with the presence of VAN, which induced the strongly reduced electrochemical signal. On account of dual amplification strategies, the performance of the aptasensor was significantly improved to achieve ultrasensitive detection of VAN. Under optimal conditions, the linear relationship was fitted for VAN with a linear range of 2 pM - 0.2 mM and the detection limit of 1.14 pM (S/N = 3). Furthermore, this assay for VAN has excellent specificity, long-term stability, and satisfactory results of the detection in the real samples. In summary, the aptasensor could be further used for the specific quantitative determination of other targets in foods. [Display omitted] • MOF-based nanocomposites of both AuNPs/NH 2 -MOF-235(Fe)/PEI-rGO and AuNPs/Ce-MOF were used for signal amplification. • RecJf exonuclease was used for target recycling. • Ultrasensitive detection of vanillin with a detection limit of 1.14 pM achieved by the dual signal amplification strategy • This developed aptasensor was successfully applied to detect vanillin in the chocolate, milk, and juice samples. [ABSTRACT FROM AUTHOR]

Herein, PtPd nanoparticles compound polyethyleneimine-functionalized reduced graphene oxide (PtPd NPs/PEI-rGO) was used as the substrate material, Exonuclease III (Exo III)-assisted triple-amplified was integrated into electrochemical platform for the detection of deoxynivalenol (DON). PtPd NPs/PEI-rGO as the substrate material increased the surface area of the electrode and improved the conductivity of the electrode. The specific binding of the DON and the aptamer triggered Exo III-assisted cyclic amplification in sample solution and generated trigger (Tr) (cycle I). The hybridization of Tr and Locking probe (LP) activated DNA Walker (W-DNA) (cycle II). Then, W-DNA run continuously with the assistance of Exo III, eventually the current signal was decreased (cycle III). However, in the absence of DON, DNA machine was not driven and the electric signal was relatively high. Under optimal conditions, the detection limit of the aptasensor is 6.9 × 10−9 mg mL−1, and the detection range from 1 × 10−8 mg mL−1 to 1 × 10−4 mg mL−1. In addition, the stability, reproducibility, and real sample detection ability of the aptasensor were studied and obtained satisfactory results. • PtPd NPs/PEI-rGO was used as the substrate material. • DON aptamers were used as biological recognition elements to ensure the selectivity of aptasensor. • The DNA walking machine assisted by Exo Ⅲ realizes effective signal amplification. [ABSTRACT FROM AUTHOR]

• A lable-free immunosensor based on the PEI-rGO/Pt@Au NRs was fabricated. • PEI-rGO/Pt@Au NRs have good stability, conductivity and large specific surface area. • The detection limit of the immunosensor was 0.02 pg/mL. In this work, we design an immunosensor for zearalenone (ZEN) detection with PEI-rGO/Pt@Au NRs nanocomposite as the modification material. PEI-rGO/Pt@Au NRs nanocomposite have good stability, conductivity and a large specific surface area, so they are chosen as the substrate material for the modified electrode, which is beneficial in improving the detection performance of the sensor. When antibody binds to ZEN, the current signal decreases, and the response signal changes after ZEN incubation, recorded by differential pulse voltammetry (DPV) methods. Under the optimised conditions, the electrochemical response of the constructed immunosensor shows a linear relation to a wide concentration range from 1 pg/mL to 1 × 106 pg/mL with a detection limit of 0.02 pg/mL. Additionally, the proposed electrochemical immunosensor has high selectivity, good stability and great potential for the trace detection of ZEN in real samples. [ABSTRACT FROM AUTHOR]

In view of the urgent need to determine polychlorinated biphenyls (PCBs) in the environment, we report a simple and sensitive electrochemical aptasensor to detect 3,3′,4,4′-tetrachlorobiphenyl (PCB77) based on Exonuclease III-powered Deoxyribonucleic Acid (DNA) walking machine using poly (diallyldimethylammonium chloride) (PDDA), which was functionalized hollow porous graphitic carbon nitride/ Ni-Co hollow nanoboxes/ Au-Pd-Pt nanoflowers composite material. Upon the addition of PCB77, the specific binding between PCB77 and the aptamer (Apt) could trigger the Exo III-assisted cyclic amplification process and release unlocking probes to deblock the Swing arm/Blocker duplex. Finally, the hybridized hairpin 3 (HP3), a short oligonucleotide, was left on the electrode via Exo III digestion of hybridized HP2, and thus a strong methylene blue (MB) signal was obtained. As expected, the proposed aptasensor exhibits exceptional PCB77 detection performances with a very low detection limit of 5.13 pg/L and a wide linear range of 0.01–100 ng/L based on the calibration curve. Moreover, the aptasensor presents a high level of selectivity and stability, with an acceptable degree of reproducibility. The results of this study have indicated that the proposed aptasensor has great potential application prospects, as demonstrated by its successful use in real environmental water samples. [Display omitted] • The HP-C 3 N 4 /Ni-Co NBs/Au-Pd-Pt NFs nanocomposite is employed as sensing platform. • DNA walking machine improved the sensitivity of the aptasensor obviously. • Aptasensor for PCB77 detection in the real samples can be achieved. • The proposed sensor showed a low detection limit of 5.13 pg/L. [ABSTRACT FROM AUTHOR]