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Here, we develop an all-in-one strategy for efficient assembly of an electrochemical aptasensor. A multifunctional structure based on a tetrahedral DNA nanostructure (TDN) was synthesized via a one-step annealing process, providing DNA fixation, target recognition, signal amplification and space regulation. Based on the integration of this multifunctional structure, the sensing interface was assembled in one step. A ratiometric aptasensor was constructed by anchoring methylene blue (MB) to the TDN and ferrocene (Fc) on the cDNA. Using the ratio of the currents obtained from Fc and MB as a measure, the developed aptasensor shows excellent analytical performance for fumonisin B1 detection. This strategy is universal and could simplify the fabrication of aptasensors. [ABSTRACT FROM AUTHOR]

Fumonisin B1 (FB1) is common contaminant in agricultural and food products, and sensors with high sensitivity and broad dynamic range are extremely required for FB1 determination. Herein, we reported the tetrahedral DNA nanostructure (TDN)-enabled electrochemical aptasensor for FB1 detection at sub-fg mL−1 level with a dynamic range of 7-folds magnitude. TDN with side length of 5.67 nm was designed to fabricate the substrate for FB1 aptamer anchoring, aiming to achieve the controllable and stable assembly of sensing interface by tuning the assembly density of TDN; TDN at the electrode acts as the anchor for aptamer, absorption of methylene blue as signal generator. Assistant aptamer was added into the sample solution to deplete FB1, reducing the amount of free FB1, thereby extending dynamic range of sensing system. Simultaneously, the negatively-charged TDN can efficiently depress absorption of free aptamer in sample solution. In this way, the utilization of TDN helps to enable the sensor with higher sensitivity and extended dynamic range for FB1. Consequently, the developed sensor allowed a linear dynamic range of 0.500 fg mL−1~1.00 ng mL−1, while the limit of detection was offered to be 0.306 fg mL−1, which was the lowest among the available methods. The applicability of aptasensor was validated by rice sample analysis, which exhibited the comparable reliability of liquid-chromatography tandem mass spectrometry/mass spectrometry. Our work has provided an efficient sensing platform for FB1, and the strategy can be also extended to fabricate sensors for other mycotoxins. • TDN was applied to controllable assembly of sensing interface, which endowed aptasensor with the lowest LOD among all reported sensors for FB1. • Negatively-charged TDN was subtly applied to generate electrostatic repulsion on assistant aptamer, addressing the impact of interfering substances. • TDN was smartly adsorbed methylene blue to generate large and stable redox current. [ABSTRACT FROM AUTHOR]

The development of accurate and reliable sensor for on-site detection of microcystin-LR (MC-LR), one of hazardous environmental pollutants, is highly required. Herein, a laser induced graphene (LIG)-based electrochemical aptasensor for sensitive on-site detection of MC-LR was reported. LIG electrode, the substrate of aptasensor, was prepared via thermal transfer with ethylene-vinyl acetate copolymer, and LIG acted as quasi-reference electrode to replace conventional Ag/AgCl electrode for better operability and robustness. LIG electrode provided large surface area to assemble tetrahedral DNA to absorb methylene blue (MB) for the signal amplification. For detection, the specific recognition of MC-LR with aptamer led to the stripping of tetrahedral DNA complex and further the decreased redox current of MB (I MB). Consequently, the fabricated aptasensor offered high analytical performance for MC-LR detection with a linear range of 1 × 10-2-1 × 105 pM and a detection limit of 3 × 10-3 pM, which was successfully used for water sample analysis with comparable reliability and accuracy of standard method. Furthermore, a portable detection platform by coupling of LIG-based electrochemical aptasensor with electrochemical workstation was constructed for on-site detection of MC-LR. This work offers a novel method for the on-site monitoring of MC-LR, which promotes the investigation of LIG-based electrochemical biosensing in the field of environmental analysis. [ABSTRACT FROM AUTHOR]