An aptasensor for cadmium ions detection based on PEI-MoS2@Au NPs 3D flower-like nanocomposites and Thi-PtPd NPs core-shell sphere.

A novel ultrasensitive electrochemical aptasensor was proposed for quantitative detection of Cd2+. To this end, flower-like polyethyleneimine-functionalized molybdenum disulfide-supported gold nanoparticles (PEI-MoS2 NFs@Au NPs) were used as substrates for the modification of bare gold electrodes (AuE). PEI-MoS2 NFs@Au NPs not only possessed excellent biocompatibility and large specific surface area to enhance the cDNA loading capacity, but also possessed good conductivity to accelerate the electron transfer rate. Furthermore, the preparation of dendritic platinum-palladium nanoparticles (PtPd NPs) can effectively load Cd2+-aptamer. Thionine and aptamers were loaded onto PtPd NPs to construct Thi-PtPd NPs-aptamer signal probes. The signal probes were captured by the cDNA immobilized on the electrode via base-pairing rule, and the signal of Thi was detected by differential pulse voltammetry (DPV). In the presence of Cd2+, aptamer-cDNA unwinded, and the combination of aptamer and Cd2+ caused the signal probes to fall off the electrode and the electrical signal decreases. Under optimal conditions, the proposed aptasensor exhibited a linear relationship between the logarithm of Cd2+ concentration and the current response over a wide range of 1 × 10-3 nM to 1 × 102 nM, with a detection limit of 2.34 × 10-4 nM. At the same time, the aptasensor was used to detect Cd2+ in tap water with satisfactory results. In addition, it has good reproducibility, selectivity and stability, and has broad application prospects in heavy metal analysis.

Electrochemical aptasensor based on the target-induced strand displacement strategy-driven for T-2 toxin detection.

Herein, an aptasensor based on target-induced strand displacement (TISD) strategy was developed for sensitive detection of T-2 toxin. Gold nanoparticles@ aminated manganese dioxide (AuNPs@NH2-MnO2) exhibited excellent electrical conductivity and provided more binding sites for aptamer (Apt). Besides, polyethyleneimine-reduced graphene oxide/gold­platinum core-shell nanorods composites (PEI-rGO/Pt@Au NRs) were used to be carriers for signaling tags, as their sufficiently large specific surface area improved the loading capacity for signal molecules. In the presence of T-2, the Apt sequence was more inclined to form an Apt-T-2 complex, and the cDNA was displaced from the Apt-cDNA duplex, while the signal tag was released, resulting in a weakened MB signal, differential pulse voltammetry (DPV) was used to record the signal change. Under optimal conditions, the signal response of the constructed electrochemical aptasensor exhibited a good linear relationship with the concentration of T-2. The detection limit was 8.74 × 10-7 ng mL-1over a wide range of concentration from 5 × 10-6 ng mL-1 to 5 ng mL-1. Furthermore, the proposed aptasensor had excellent specificity, good stability and can be well applied to the detection of real samples. It provided a new avenue for the research and development of sensitive aptasensors in food detection and analysis.

Sensitive and reversible perylene derivative-based fluorescent probe for acetylcholinesterase activity monitoring and its inhibitor.

A reversible fluorescence probe for acetylcholinesterase activity detection was developed based on water soluble perylene derivative, N,N'-di(2-aspartic acid)-perylene-3,4,9,10-tetracarboxylic diimide (PASP). Based on the photo-induced electron transfer (PET), PASP fluorescence in aqueous is quenched after combining with copper ions (Cu2+). Acetylcholinesterase (AChE) is well known to catalyze the hydrolysis of acetylcholine (ATCh) to produce thiocholine, whose affinity is strong enough to capture Cu2+ by thiol (-SH) group from the complex PASP-Cu, resulting in the fluorescence signal of PASP recovers up to 90%. This optical switch is highly sensitive depended on the coordination and dissociation between PASP and Cu2+. We proposed its application for AChE activity detection, as well as its inhibitor screening. According to the change of fluorescence intensity, quantifying the detection limit of AChE was 1.78 mU·mL-1. Classical inhibitors, tacrine and organophosphate pesticide diazinon, were further evaluated for drug screening. The IC50 value of tacrine was calculated to be 0.43 µM, and the detection limit of diazinon was 0.22 µM. Both of these performances were much better than previous results, revealing our probe is sensitive and reversible for screening applications.