ß-Cyclodextrin Stabilized Nanoceria for Hydrolytic Cleavage of Paraoxon in Aqueous and Cationic Micellar Media.

Beta-cyclodextrin (ß-CD) stabilized cerium oxide nanoparticles (ß-CD@CeO2 NPs) were synthesized through a hydrothermal route. The electronic properties, surface functional group, surface composition, size, and morphologies of the as-synthesized ß-CD@CeO2 NPs were characterized using UV-visible spectroscopy, FTIR analysis, high resolution X-ray photoelectron spectroscopy (HRXPS), high resolution transmission electron microscopy (HRTEM), and field emission scanning electron microscopy (FESEM). The pH-dependent variation of the ζ-potential of ß-CD@CeO2 NPs and the catalytic activity of the NPs for the hydrolysis of paraoxon were investigated. The observed pseudo-first-order rate constant (kobs) for the hydrolysis of paraoxon is increased with increasing pH and the ζ-potential of ß-CD@CeO2 NPs. The kinetics and mechanism of hydrolysis of paraoxon in the aqueous and cationic micellar media have been discussed.

A colorimetric nanoprobe based on enzyme-immobilized silver nanoparticles for the efficient detection of cholesterol.

A large number of cardiovascular diseases have recently become of serious concern throughout the world. Herein, we developed a colorimetric probe based on functionalized silver nanoparticles (AgNPs) for the efficient sensing of cholesterol, an important cardiovascular risk marker. A simple sodium borohydride reduction method was employed to synthesize the AgNPs. The cholesterol oxidase (ChOx)-immobilized AgNPs interact with free cholesterol to produce H2O2 in proportion to the concentration of cholesterol, resulting in decreased AgNP absorbance (turn-off) at 400 nm due to electron transfer between the AgNPs and H2O2. The response of the sensor can also be observed visually. The absorption intensity of the AgNPs is recovered (turn-on) upon the addition of sodium dodecyl sulfate due to the inhibition of ChOx. This on-off mechanism was effectively applied to detect cholesterol within the concentration range 10-250 nM with a low detection limit of approximately 0.014 nM. Moreover, the selectivity of the sensor toward cholesterol was analyzed in the presence of a range of interfering organic substances such as glucose, urea, and sucrose. Finally, the potential of the proposed sensor was evaluated using real samples.