Stability of nano-sized permethrin in its colloidal state and its effect on the physiological and biochemical profile of Culex tritaeniorhynchus larvae.

The occurrence of pesticidal pollution in the environment and the resistance in the mosquito species makes an urge for the safer and an effective pesticide. Permethrin, a poorly water-soluble pyrethroid pesticide, was formulated into a hydrodispersible nanopowder through rapid solvent evaporation of pesticide-loaded oil in water microemulsion. Stability studies confirmed that the nanopermethrin dispersion was stable in paddy field water for 5 days with the mean particle sizes of 175.3 ± 0.75 nm and zeta potential of -30.6 ± 0.62 mV. The instability rate of the nanopermethrin particles was greater in alkaline (pH 10) medium when compared with the neutral (pH 7) and acidic (pH 4) dispersion medium. The colloidal dispersion at 45°C was found to be less stable compared with the dispersions at 25 and 5°C. The 12- and 24-h lethal indices (LC50) for nanopermethrin were found to be 0.057 and 0.014 mg l-1, respectively. These results were corroborative with the severity of damages observed in the mosquito larvae manifested in epithelial cells and the evacuation of the midgut contents. Further, the results were substantiated by the decrease in cellular biomolecules and biomarker enzyme activity in nanopermethrin treated larvae when compared to bulk and control treatment.

Rapid and selective detection of viruses using virus-imprinted polymer films.

We prepared a nanopatterned polymer film of polydimethylsiloxane (PDMS) via virus imprinting. The imprinted surface exhibited nanoscale cavities with the mean size of 120 ± 4 nm. These cavities demonstrated the ability to preferentially capture a target virus from an aqueous suspension of ultralow volume (5 µL) after only 1 minute of contact. Two inactivated viruses with similar shape, Influenza A (HK68) and Newcastle Disease Virus (NDV), were employed as model pathogens. The polymer film, which was first imprinted with HK68 and exposed sequentially to suspensions containing fluorescently labeled NDV and HK68, was able to preferentially bind HK68 at a capture ratio of 1 : 8.0. When we reversed the procedure and imprinted with NDV, the capture ratio was 1 : 7.6. These results were obtained within 20 minutes of static exposure. The suspensions contained viruses at concentrations close to those occurring physiologically in influenza infections. The limit of detection was approximately 8 fM. Production of virus-imprinted films can be readily scaled to large quantities and yields a disposable, simple-to-use device that allows for rapid detection of viruses.

Active curcumin nanoparticles formed from a volatile microemulsion template.

We report on biological performance of organic nanoparticles formed by a simple method based on rapid solvent removal from a volatile microemulsion. The particular focus of the study was on testing the suitability of the method for substances soluble in partially water-miscible organic solvents as well as on evaluating the therapeutic activity of the resultant nanoparticles. Curcumin was employed as a model for hydrophobic drug, and, as it is soluble in water-miscible organic solvents, it was successfully incorporated into a new cyclopentanone-water microemulsion system. During rapid solvent removal by spray-drying, the nanometric droplets of the microemulsion were converted into nanoparticles containing amorphous curcumin with the average size of 20.2±3.4 nm, having ζ potential of -36.2 ±1.8 mV. These nanoparticles were dispersible in water and retained the high loading of the active substance. The therapeutic activity of the resulting nanoparticles was demonstrated in a pancreatic cancer cell line Panc-1. The effective concentration for reducing the metabolic activity was found to be 11.5 µM for nanoparticles compared with 19.5 µM for free curcumin.