Acetylcholine triggered enzymatic cascade reaction based on Fe7S8 nanoflakes catalysis for organophosphorus pesticides visual detection.

BACKGROUND: Organophosphorus pesticides (OPs) play important roles in the natural environment, agricultural fields, and biological prevention. The development of OPs detection has gradually become an effective strategy to avoid the dangers of pesticides abuse and solve the severe environmental and health problems in humans. Although conventional assays for OPs analysis such as the bulky instrument required analytical methods have been well-developed, it still remains the limitation of inconvenient, inefficient and lab-dependence analysis in real samples. Hence, there is an urgent demand to develop efficient detection methods for OPs analysis in real scenarios. RESULTS: Here, by virtue of the highly efficient catalytic performance in Fe7S8 nanoflakes (Fe7S8 NFs), we propose an OPs detection method that rationally integrated Fe7S8 NFs into the acetylcholine (ACh) triggered enzymatic cascade reaction (ATECR) for proceeding better detection performances. In this method, OPs serve as the enzyme inhibitors for inhibiting ATECR among ACh, acetylcholinesterase (AChE), and choline oxidase (CHO), then reduce the generation of H2O2 to suppress the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) that catalyzed by Fe7S8 NFs. Benefiting from the integration of Fe7S8 NFs and ATECR, it enables a sensitive detection for OPs (e.g. dimethoate). The proposed method has presented good linear ranges of OPs detection ranging from 0.1 to 10 µg mL-1. Compared to the other methods, the comparable limits of detection (LOD) of OPs are as low as 0.05 µg mL-1. SIGNIFICANCE: Furthermore, the proposed method has also achieved a favorable visual detection performance of revealing OPs analysis in real samples. The visual signals of OPs can be transformed into RGB values and gathered by using smartphones, indicating the great potential in simple, sensitive, instrument-free and on-site analysis of pesticide residues in environmental monitoring and biosecurity research.

Construction of a novel fluorescent DNA aptasensor for the fast-response and sensitive detection of copper ions in industrial sewage.

Heavy metal pollution poses a great threat to the ecological environment and human health. In particular, copper ions (Cu2+) play a vital role in regulating fundamental life behavior, and the homeostasis of Cu2+ is closely related to many physiological processes. The excessive accumulation of Cu2+ in the human body through food and drinking water will cause severe diseases. However, current conventional Cu2+ detection methods for evaluating the content of Cu2+ are unable to meet the complete requirements of practical Cu2+ analysis in the practical aquatic environment. In this work, we successfully constructed a novel fluorescent DNA aptasensor, which originated from the binding reaction between the improved DNA fluorescent light-up aptamer termed S2T3AT-GC and a small fluorescent molecule termed DFHBI-1T (S2T3AT-GC/DFHBI-1T) to realize fast and anti-interference response for Cu2+via the competitive interaction between Cu2+ and S2T3AT-GC (Cu2+/S2T3AT-GC) destroying the contained G-quadruplex structure of S2T3AT-GC. Moreover, it enables the sensitive detection of Cu2+ with a detection limit of 0.3 µM and a wide detection linear range from 0.3 to 300 µM. Moreover, with the verification of high stability in real industrial sewage samples, this aptasensor exhibits excellent detection performance for Cu2+ analysis in real water samples. Therefore, the proposed aptasensor exhibits great potential in exploring Cu2+-related environmental and ecological research.

Engineering of An Aptamer-Functionalized Fluorescent DNA Sensor for Cu(II) Responding in Living Tumor Cells.

Copper ions play vital roles in regulating life processes and being closely involved in several diseases such as cancer. Although detection methods based on fluorescent sensors or other strategies have been developed, it still remains a challenge to simultaneously realize the convenience, specificity, and accuracy in intracellular copper ion analysis. Herein, we propose an aptamer-functionalized DNA fluorescent sensor (AFDS) for accurate and specific detection of Cu(II) both in vitro and in cells by engineering the linkage of two DNA aptamers, namely, Lettuce aptamer and AS1411 aptamer, to achieve the manner of recognition response. Taking advantage of the functions of each aptamer, the tumor cell recognition capability and the high-contrast detection performance are simultaneously equipped in the AFDS. Furthermore, the AFDS shows high specificity and selectivity in Cu(II) response to avoid interference from common metal ions, chelators, and reactants by being associated with the irreversible interaction between nucleobases and Cu(II), which can destroy the topological structures and switch off the fluorescence of the AFDS. It also enables a sensitive in vitro detection of Cu(II) with a detection limit as lower as 0.1 µM and a wide detection linear range from 0.1 to 300 µM. The feasibility and superiority of the AFDS provide an opportunity to reveal both concentration-dependent and time-dependent intracellular Cu(II) responses in living cells. Therefore, the AFDS has achieved the novel detection performance of Cu(II) to exhibit great potential in exploring copper-related biological and pathological research.

Controllable synthesis of MoS2@TiO2 nanocomposites for visual detection of dopamine secretion with highly-efficient enzymatic activity.

Dopamine (DA) plays an essential role in dopaminergic neuronal behavior and disease. However, current detection methods for discriminating the secretion of DA are hampered by the limitations of the requirement for bulky instrumentation and non-intuitive signals. Herein, we have controllably and proportionately integrated molybdenum disulfide (MoS2) with titanium dioxide (TiO2) to prepare MoS2@TiO2 nanocomposites (MoS2@TiO2 NCs) via a facile synthesis method. MoS2@TiO2 NCs with a certain reactant mass ratio have shown a significant enhancement in peroxidase-like activity with superiority of the nanocomposite structure compared to single MoS2 or natural enzyme. The method for catalyzing the decomposition of H2O2 by MoS2@TiO2 NCs and competition for hydroxyl radicals (˙OH) between the chromogenic agent and DA enable a sensitive, specific, and colorimetric DA analysis with a low detection limit of 0.194 µM and a wide linear detection range (0.8 to 100 µM). Because of the favorable detection performance, we were encouraged to explore and finally realize the visual detection of cellular DA secretion that is stimulated in a High-K+ neurocyte environment. Collectively, this method will provide a promising strategy for basic research in neuroscience with its portable, sensitive, and naked-eye detectable performance.