An electrochemical aptasensor for detection of streptomycin based on signal amplification assisted by functionalized gold nanoparticles and hybridization chain reaction.

A ratiometric electrochemical aptasensor based on gold nanoparticles (AuNPs) functionalization and hybridization chain reaction (HCR) assisted signal amplification has been for the first time designed for the detection of streptomycin (STR). The double-stranded DNA (dsDNA) formed by the hybridization of ferrocene (Fc)-labeled STR aptamer (Apt) and capture probe (CP) is first immobilized on the gold electrode (GE) surface via Au-S reaction. The specific binding of the target and Apt results in numerous Fc detachment from the sensing interface. Then, the remaining single-stranded CP is combined with AuNPs modified with initiator DNA (iDNA) by auxiliary DNA (aDNA). Among them, the iDNA triggers HCR between two hairpin probes (H1/H2), thus capturing a large number of methylene blue (MB) electrochemical probe, which generates a strong electrochemical signal of MB and a weak electrochemical signal of Fc. Signals are collected by square wave voltammetry (the potential window ranging from -0.5 V to 0.6 V, vs. Ag/AgCl ), and the oxidation peak currents at -0.200 V (MB) and 0.416 V (Fc) are recorded. The use of the ratiometric method has effectively improved the accuracy and reliability of the analysis. The successful application of AuNPs and HCR greatly improves the sensitivity of the sensor, and the detection limit is as low as 0.08 pM. It can sensitively determine STR in the range 0.1 pM to 10 nM. In addition, the designed aptasensor has been successfully applied to the detection of STR in milk and honey samples.

Incompatible and sterile insect techniques combined eliminate mosquitoes.

The radiation-based sterile insect technique (SIT) has successfully suppressed field populations of several insect pest species, but its effect on mosquito vector control has been limited. The related incompatible insect technique (IIT)-which uses sterilization caused by the maternally inherited endosymbiotic bacteria Wolbachia-is a promising alternative, but can be undermined by accidental release of females infected with the same Wolbachia strain as the released males. Here we show that combining incompatible and sterile insect techniques (IIT-SIT) enables near elimination of field populations of the world's most invasive mosquito species, Aedes albopictus. Millions of factory-reared adult males with an artificial triple-Wolbachia infection were released, with prior pupal irradiation of the released mosquitoes to prevent unintentionally released triply infected females from successfully reproducing in the field. This successful field trial demonstrates the feasibility of area-wide application of combined IIT-SIT for mosquito vector control.