An electrochemical aptasensor for zearalenone detection based on the Co3O4/MoS2/Au nanocomposites and hybrid chain reaction.

An electrochemical aptasensor was used for the fast and sensitive detection of zearalenone (ZEN) based on the combination of Co3O4/MoS2/Au nanocomposites and the hybrid chain reaction (HCR). The glassy carbon electrode was coated with Co3O4/MoS2/Au nanomaterials to immobilize the ZEN-cDNA that had been bound with ZEN-Apt by the principle of base complementary pairing. In the absence of ZEN, the HCR could not be triggered because the ZEN-cDNA could not be exposed. After ZEN was added to the surface of the electrode, a complex structure was produced on the modified electrode by the combination of ZEN and ZEN-Apt. Therefore, the ZEN-cDNA can raise the HCR to produce the long-strand dsDNA structure. Due to the formation of dsDNA, the methylene blue (MB) could be inserted into the superstructure of branched DNA and the peak currents of the MB redox signal dramatically increased. So the concentration of ZEN could be detected by the change of signal intensity. Under optimized conditions, the developed electrochemical biosensing strategy showed an outstanding linear detection range of 1.0×10-10 mol/L to 1.0×10-6 mol/L, a low detection limit (LOD) of 8.5×10-11 mol/L with desirable selectivity and stability. Therefore, the fabricated platform possessed a great application potential in fields of food safety, medical detection, and drug analysis.

A novel colorimetric assay for sensitive detection of kanamycin based on the aptamer-regulated peroxidase-mimicking activity of Co3O4 nanoparticles.

Kanamycin is used widely in livestock farming due to its antimicrobial properties and low cost, but has led to antibiotic residues in food, which can damage human health. Therefore, there is an urgent need for convenient technology that can be used to detect kanamycin rapidly. We found that Co3O4 nanoparticles (NPs) possessed peroxidase-like activity that catalyzed the oxidation of 3,3',5,5'-tetramethylbenzidine to change color. Interestingly, a target-specific aptamer could regulate the catalytic activity of Co3O4 NPs and inhibit this effect through aptamer-target binding. On the basis of a colorimetric assay combined with an aptamer-regulatory mechanism, the linear range for quantitative detection of kanamycin was 0.1-30 µM, the minimum limit of detection was 44.2 nM, and the total time needed for detection was 55 min. Moreover, this "aptasensor" displayed excellent selectivity and could be applied to detect KAN in milk samples. Our sensor might have promising applications for kanamycin detection in animal husbandry and agricultural products.

Nonlinear Dynamic Analysis of Axially Moving Laminated Shape Memory Alloy Beam with 1:3 Internal Resonance.

The remarkable properties of shape memory alloys (SMA) are attracting significant technological interest in many fields of science and engineering. In this paper, a nonlinear dynamic analytical model is developed for a laminated beam with a shape memory alloy layer. The model is derived based on Falk's polynomial model for SMAs combined with Timoshenko beam theory. In addition, axial velocity, axial pressure, temperature, and complex boundary conditions are also parameters that have been taken into account in the creation of the SMA dynamical equation. The nonlinear vibration characteristics of SMA laminated beams under 1:3 internal resonance are studied. The multi-scale method is used to solve the discretized modal equation system, the characteristic equation of vibration modes coupled to each other in the case of internal resonance, as well as the time-history and phase diagrams of the common resonance amplitude in the system are obtained. The effects of axial velocity and initial conditions on the nonlinear internal resonance characteristics of the system were also studied.