Marie-Hélène Charles

Amino-containing cationic latex–oligodeoxyribonucleotide conjugates: application to diagnostic test sensitivity enhancement

Abstract The covalent immobilization of nucleic acid probes (ODN) onto amino-containing cationic hydrophobic (polystyrene) or hydrophilic poly( N -isopropylacrylamide) latexes has been investigated. A preliminary study was devoted to the adsorption behavior of ODNs as a function of pH, ionic strength and type of latex. A drastic reduction of ODN adsorption upon increasing ionic strength was found, especially with hydrophilic-based latexes. Then, covalent attachment of ODNs onto the reactive particles was performed in a basic pH (>9) so as to avoid physical adsorption. Coating of the ODN–latex conjugates onto solid surfaces resulted in the formation of two dimensional assemblies. These functionalized surfaces were finally used for the detection of the HBV virus DNA, providing sensitivity improvement identical to what was already observed with linear polymers.

Impedance analysis of Si/SiO2 heterostructures grafted with antibodies : an approach for immunosensor development

The feasibility of an immunosensor on the basis of impedance analysis has been studied. The measurements were performed in a classical three-electrode electrochemical cell. As a sensitive element a Si/SiO2 heterostructure was used grafted with anti-α-fetoprotein antibodies through three different coupling reagents: aminosilane, cyanosilane and polysiloxane membranes. Promising results have been obtained in such a system with polysiloxane membranes (after antigen-containing analyte incubation) through an analysis of impedance variations. The dynamic range of this sensor is between 10 and 150 ng ml−1. The results presented show good selectivity, reproducibility, and storage stability for the immunosensor, at least during 50 days of storage in PBS at +4°C.