A ratiometric fluorescence aptasensor based on photoinduced electron transfer from CdTe QDs to WS2 NTs for the sensitive detection of zearalenone in cereal crops.

Semiconductor quantum dots (QDs) and tungsten disulfide nanosheets (WS2 NTs) have been widely studied in photocatalysis and photoelectrochemistry as representative electron donor-acceptor pairs but rarely in fluorescence sensing. In this study, we investigated the effect of WS2 NTs on the fluorescence signal of cadmium telluride (CdTe) QDs by grafting an aptamer as a bridge between them. The corresponding quenching mechanism was systematically explored, and results described the photoinduced electron transfer (PET) from excited CdTe QDs to WS2 NTs. Based on these results, a novel ratiometric fluorescence aptasensor was developed for zearalenone (ZEN) determination by innovatively introducing exonuclease I to digest the aptamer of ZEN and control the PET between CdTe QDs and WS2 NTs. The designed aptasensor exhibited an acceptable linear range and detection limit (0.1 pg mL-1), and superior accuracy and selectivity. This ratiometric fluorescence aptasensor was also used to monitor ZEN in rice and corn flour.

Sensitivity programmable ratiometric electrochemical aptasensor based on signal engineering for the detection of aflatoxin B1 in peanut.

Accurately monitoring of aflatoxin B1 (AFB1), the most hazardous mycotoxin in agricultural products, is essential for the public health, but various testing demands (e.g. detection range, sensitivity) for different samples can be challenging for sensors. Here, we developed a sensitivity-programmable ratiometric electrochemical aptasensor for AFB1 analysis in peanut. Thionine functionalized reduced graphene oxide (THI-rGO) served as reference signal generator, ferrocene-labelled aptamer (Fc-apt) output the response signal. During analysis, the formation of Fc-apt-AFB1 complex led to its stripping from the electrode and faded the current intensity of Fc (IFc), while the current intensity of THI (ITHI) was enhanced. And ratiometric detection of AFB1 was achieved by using the current intensity ratio (ITHI/IFc) as quantitative signal. Compared with ratiometric strategies that highly rely on the labelled aptamers, the proposed strategy could regulate the value of ITHI/IFc by changing the modification of Fc-apt. And the detection sensitivity was found to be closely related to ITHI/IFc. Under the optimal conditions, the fabricated aptasensor with a dynamic range from 0.05-20 ng mL-1 and a detection limit of 0.016 ng mL-1 for AFB1 analysis. Besides, it exhibited excellent selectivity, reliability and reproducibility. The proposed sensitivity-programmable biosensor can be applied to detect various aptamer-recognized mycotoxins in agricultural sensing.

Rhinophore bio-inspired stretchable and programmable electrochemical sensor.

Rhinophore, a bio-chemical sensory organ with soft and stretchable/retractable features in many marine molluscs species, exhibits tunable chemosensory abilities in terms of far/near-field chemical detection and molecules' source orientation. However, existing artificial bio-chemical sensors cannot provide tunable modality sensing. Inspired by the anatomical units (folded sensory epithelium) and the functions of a rhinophore, this work introduces a stretchable electrochemical sensor that offers a programmable electro-catalytic performance towards glucose based on the fold/unfold regulation of the gold nanomembrane on an elastic fiber. Geometrical design rationale and covalent bonding strategy are used to realize the robust mechanical and electrical stability of this stretchable bionic sensor. Electrochemical tests demonstrated that the sensitivities of the as-prepared bionic sensor exhibit a linear relationship with its strain states from 0% to 150%. Bio-inspired sensory functions are tested by regulating the strain of the bionic sensor. The sensor achieves a sensitivity of 195.4 µA mM-1 in a low glucose concentration range of 8-206 µM at 150% strain for potentially far-field chemical detection, and a sensitivity of 14.2 µA mM-1 in a high concentration range of 10-100 mM at 0% strain for near-field chemical detection. Moreover, the bionic sensor performs the detection while extending its length can largely enhance the response signal, which is used to distinguish the molecules' source direction. This proposed bionic sensor can be useful in wearable devices, robotics and bionics applications which require diverse modality sensing and smart chemical tracking system.