Saloua Helali

Labeled magnetic nanoparticles assembly on polypyrrole film for biosensor applications.

In recent years, conducting polymers combined with metallic nanoparticles have been paid more attention due to their potential applications in microelectronics, microsystems, optical sensors and photoelectronic chemistry. The work presented in this paper describes the preparation and characterization of a nanocomposite composed by a thin polypyrrole (PPy) film covered with an assembly of magnetic nanoparticles (NPs). The magnetic particles were immobilized on PPy films under appropriate magnetic field in order to control their organization on the PPy film and finally to improve the sensitivity of the system in potential sensing applications. The electrical properties and morphology of the resulting PPy film and the PPy film/NPs composite were characterized with cyclic voltammetry, impedance spectroscopy (IS), scanning electron microscopy (SEM), atomic force microscopy (AFM) and infra-red spectroscopy (IR). By using streptavidin labeled magnetic particles it was possible to functionalize the NPs assembly with biotin-Fab fragment K47 antibody. The designed biosensor had been successfully applied in rapid, simple, and accurate measurements of atrazine concentrations, with a significantly low detection limit of 5 ng/ml.

Improvement of a pesticide immunosensor performance using site-directed antibody immobilisation and carbon nanotubes

The potential toxicity of pesticide residues in drinking water has meant a rigid regulation for the appearance of these pollutants. Thus, in this work, we developed a new immunosensor for atrazine detection. We focused on the optimisation of the antibody immobilisation method on sensor surface for the enhancement of the biosensor sensitivity. First, with site–directed immobilisation of rabbit anti–atrazine antibodies using goat anti–rabbit immunoglobulin, a detection limit of 0.5 ng/mL was obtained. This value is 20 times lower than the detection limit obtained with non–oriented antibodies. The second way to improve immunosensor sensitivity consisted of the addition of carbon nanotubes (CNT). As result of using these CNT, detection limit has been improved again from 0.5 ng/mL to 100 pg/mL.

Electrical Impedance Spectroscopy Using Single Wall Carbon NanotubesCarboxlic Acid Functionalized: Detection of Copper in Tabuk-Kingdom ofSaudi Arabia Water

Copper (Cu) is an essential element in mammalian nutrition. Since both copper deficiency and copper excess produce adverse health effects, so it is important to develop simple, sensitive and accurate methods for their detection in environment and food. In this study, the absorption of the copper ion in single wall carbon nanotubes carboxylic acid functionalized (SWCNTCOOH) was studied in buffer saline (PBS) and in Tabuk, kingdom of Saudi Arabia water. The gold electrode is functionalized with the self-assembled monolayer technique. The modified surface is activated with EDC/NHS for SWCNT-COOH immobilization. Each grafted layer on the gold electrode was characterized with cyclic voltammetry, impedance spectroscopy and Fourrier Transform Infra-Red spectroscopy (FTIR). The high insulating properties of the acidic thiol monolayer has been proved by cyclic voltammetry and impedance spectroscopy. The increases in DC current and the decrease in impedance confirm the conducting properties of the SWCNT-COOH layer. The development of sensor for copper detection was observed with the impedance spectroscopy. During impedance measurements, the charge transfer resistance increased significantly after absorption the copper in both buffer. The response of the developed sensor was very sensitive in the range of 10-300 ng/ml. The result show that the signal in Tabuk water is four time large relative to the signal in PBS.