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In this work, a sandwich-type electrochemical biosensing platform is developed based on carbon sphere-MoS 2 (CS-MoS 2 ) and target recycling amplification of catalyzed hairpin assembly (CHA) strategy for ultrasensitive determination of microRNA (miRNA). The CS-MoS 2 is prepared and used as sensing substrate, which shows high specific surface area, enhanced stability and good dispersibility. The capture probe is first modified on Au nanoparticles/CS-MoS 2 modified glassy carbon electrode through Au-S band, and hairpin DNA1 (H1) then reacts with it and unfolds its loop domain by hybridizing with target miRNA-21. The opened H1 subsequently assembles with biotin labeled hairpin DNA 2 (H2) to displace the target. The liberated miRNA-21 is free and backs to the original solution to proceed next circulation, resulting in the generation of large amounts of H1–H2 duplex. Massive signal indicators horseradish peroxidase are then immobilized on electrode, and catalyze hydrogenperoxide + hydroquinone (H 2 O 2  + HQ) system to produce a strong electrochemical response. The proposed assay benefits from advantages of sandwich-type structure, favorable electrochemical properties of CS-MoS 2 and CHA target recycling amplification strategy. Therefore, it exhibits a wide linear relation between 1 × 10 −16 and 1 × 10 −10  M with a low detection limit of 1.6 × 10 −17  M for miRNA-21 detection. [ABSTRACT FROM AUTHOR]

In view of the urgent demand to determine neonicotinoid insecticides in real samples, we first report a photothermal-induced partial Leidenfrost superhydrophobic (PIPLS) sensor using gold colloid and highly roughened SiO 2 /PDMS surface coupled with few-layered MXene (Ti 3 C 2) nanosheets for the ultrasensitive surface-enhanced Raman scattering (SERS) detection of neonicotinoid insecticides. Under the remote control of near-infrared light, the temperature of the sensor can rise to 170 ℃ within 10 s due to the significant photothermal effect of MXene, resulting in the partial Leidenfrost evaporation phenomenon and effectively reducing the contact area between the droplet of gold colloid and the surface. Analyte concentration factors obtained from the PIPLS SERS sensor were 5.1-fold and 30.3-fold higher than those attainable by conventional superhydrophobic and hydrophobic surfaces, respectively. Due to the significant enrichment capability, the PIPLS SERS sensor detected analytes down to the fM level with a high enhancement factor (5.1 × 1011). Based on the principal component analysis method, the PIPLS SERS sensor effectively discriminated neonicotinoid insecticides (acetamiprid, clothianidin, imidacloprid, and thiamethoxam). The reliable detection of neonicotinoid insecticides in real samples, including apple, green tea, wheat, and corn, also demonstrates the applicability of the PIPLS SERS sensor for pesticide sensing in real-world settings. [Display omitted] • Photothermal-induced partial Leidenfrost effect was used to improve SERS performance. • Highly roughened Ti 3 C 2 /SiO 2 /PDMS surface has significant photothermal effect. • The proposed method is applied for neonicotinoid insecticides detection in real samples. • This work was demonstrated to have high sensitivity down to fM with only 5 μL sample. • Stability and practicality of the method have been verified. [ABSTRACT FROM AUTHOR]

Sensitive detection of ochratoxin A (OTA) plays an important role in the field of food safety control. In this study, we are reporting for the first time an electrochemical biosensor which employs the integration of MoSe 2 nanoflowers, Au nanoparticles (AuNPs), aptamer and the guanine-rich complementary DNA sequence for the sensitive detection of OTA. MoSe 2 nanoflowers are prepared by a simple hydrothermal method and used as a promising sensing platform based on its large surface area. The methylene blue is used as a tracer and a guanine-rich complementary DNA sequence is designed to bind with the unbound OTA aptamer for signal amplification. The aptamer is immobilized on the AuNPs/MoSe 2 modified electrode surface through Au–S interaction. Since OTA can competitively bind with the aptamer due to their high affinity, the presence of OTA will induce the decrease of guanine-rich DNA on the electrode surface, in turn reduces the signal of methylene blue which can specifically adsorb to the guanine units of DNA. The proposed assay shows a good linear relationship within the range of 0.0001–1 nM with a detection limit of 0.08 pM for OTA. The developed biosensor has been applied to determine OTA concentration in wine samples. [ABSTRACT FROM AUTHOR]