No abstract

An amperometric enzyme biosensor for the direct measurement of parathion was developed. The biosensor is based on parathion hydrolase from Pseudomonas sp. isolated from contaminated soil. The enzyme, which was immobilized on a carbon electrode, catalyzes the hydrolysis of parathion to form p-nitrophenol, which was detected by its anodic oxidation. The enzymatic and electrochemical reactions were examined and optimized. Screen-printed electrodes and a microflow injection system provide the means to significantly reduce the volume of the detected samples. Pulsed techniques further increased the sensitivity of the measurement. The current signal was linearly related to the parathion concentration, and the detection limit was less than 1 ng/mL. The biosensor is rapid as well and can be used outdoors and indoors by a nonqualified person.

No abstract

Abstract-The growing awareness worldwide ove r the deleterious effects of endocrine disruptors on human health has created a need for screening systems to detect xenoestrogens, a diverse group of chemicals that mimic estrogenic actions and are assumed to decrease mail fertility and induce hormone related cancers in females. Here we describe a novel, classselective detector that uses fast impedance measurements to monitor the binding of estrogen and xenoestrogens to a native estrogen receptor. We embedded the receptor in synthetic lipid bilayers attached to gold electrodes. The lipid bilayers serve as electrical circuits constructed of resistors and a capacitors. Estrogen binding to the receptor-modified electrode is immediately followed by conformational changes in the lipid layer, leading to alterations of the electrical circuit components that are detected by fast impedance measurements. The electrochemical system enabled characterization of changes in the bilayer structure and quantification of estrogen binding to the receptor. To assess the effectiveness of the method for detecting estrogenic chemicals, we chose two classes of xenoestrogens: bisphenol-A, a synthetic xenoestrogen, and genistein, a phytoestrogen. This system is highly sensitive and amenable to use on-site, providing an efficient and economic tool for measuring minuscule amounts of endocrine disrupting chemicals in environmental or human samples.