Thierry Delair

Toward intelligent polymers : DNA sensors based on oligonucleotide-functionalized polypyrroles

Abstract A conjugated polymer can be considered as tri-dimensional network of intrinsically conducting macromolecular wires, able to transport signals. When further functionalized with prosthetic groups showing recognition properties, such polymer architecture mimics the nervous system existing in living beings. With this aim, we have developed a new type of electrochemical sensors, based on electroactive polypyrrole functionalized with oligonucleotide (ODN). At first, we analyzed the experimental conditions for building such modified electrode, showing a high electroactivity in aqueous medium. We developed a new route for the functionalization of polypyrrole, involving a precursor polypyrrole bearing an easy leaving ester group, on which an amino-labelled ODN can be directly substituted. The electrochemical response of this polypyrrole electrode functionalized with an ODN probe has then been analyzed in various aqueous media, containing either complementary or noncomplementary ODN targets. Results show that the cyclic voltammogram of ODN-functionalized polypyrrole is not modified when in presence of a noncomplementary ODN in solution. On the other hand, a significant modification of the voltammogram is observed upon addition of a complementary ODN target, to the electrolytic medium, which indicates that specific hybridization has occurred between the polypyrrole-grafted ODN probe and its complementary ODN target in solution. This biological recognition can be quantitatively determined by an amperometric analysis, and the limit of detection of this electrochemical biosensor is about 10 −11 mol, without any signal processing. These results confirm that functionalized polypyrroles act as macromolecular wires able to transduce biological information into molecular signals.

Synthesis and characterization of cationic amino functionalized polystyrene latexes

Amino-functionalized latex particles were obtained batchwise by emulsion copolymerization of styrene and vinylbenzylamine hydrochloride (VBAH) in the presence of 2-2′-Azobis(2-amidinopropane) HCl (V50). Size monodispersity of the particles was improved by using divinylbenzene (DVB) as a third monomer at a 2% molar ratio. Surface amino group titration was performed spectrometrically with N-succinimidyl 3-(2 pyridyldithio)propionate (SPDP). The yields of functional monomer incorporation were up to 85%.

Synthesis and characterization of cationic latex particles bearing sulfhydryl groups and their use in the immobilization of Fab antibody fragments (1)

Emulsion copolymerization of styrene and a cationic monomer vinylbenzyl-isothiouronium chloride (VBIC) with initiation by 2,2′ azobis(2-amidinopropane)-dihydrochloride (V-50) gave monodisperse latex particles. After post-stabilization with cationic or non-ionic surfactants, the colloids were diluted in basic buffers with concomitant deprotection of the sulfhydryl groups. Therefore, coupling reactions on the latex beads were possible. Coupling conditions were determined with Ellmans reagent.14C iodoacetamide and anti C-reactive protein antibody Fab fragments were immobilized and finally, the immunological activity of the sensitized latex was assessed.

Syntheses of poly[N‐(2,2 dimethoxyethyl)‐N‐methyl acrylamide] for the immobilization of oligonucleotides

SYNOPSIS Radical-initiated polymerization of N-( 2,2 dimethoxyethyl) -N-methylacrylamide has been carried out either in chloroform or methanol using 2,2-azobisisobutyronitrile as an initiator, allowing us to prepare acetal containing water-soluble polymers. A kinetic study in both solvents showed that this monomer fairly homopolymerized (12, - k; = 1 mol-/ L/ s-/*). Static light scattering was used to characterize the molecular weight of these polymers. In addition, the Mark-Houwink-Sakurada relationship was established based on viscosity measurements performed at 25°C in water. Recovery of the aldehyde moieties on the polymer was achieved under mild conditions using a diluted inorganic solution. The analysis of the formation of aldehyde groups was performed by H- and %-NMR. The covalent binding of oligodeoxyribonucleotides was carried out in water/acetonitrile mixtures with subsequent NaBH4 reduction of the imine bonds so as to stabilize the polymer/oligodeoxynucleotide conjugates. 0 1996 John Wiley & Sons, Inc.

Preparation and properties of comb-like polymers obtained by radical homo- and copolymerization of a liposaccharidic monomer with styrene

A new disaccharide polymerizable surfactant 11-N-p-vinyl benzyl) amidoundecanoyl maltobionamide (LIMA, 6), was synthesized through a five-step procedure. It was found to exhibit a Krafft point of 52°C and a critical micelle concentration of 1.2 × 10−3 moll−1 at 55°C (as measured by surface tension and fluorescence techniques). Radical-initiated homo- and copolymerization of LIMA (M) with styrene (S) have been performed at 60°C in deuterated dimethyl sulfoxide using 2,2′-azobisisobutyronitrile as initiator. Kinetics were followed both by 1H n.m.r. and gas chromatography analyses providing kp /kt12 value for LIMA homopolymerization and a set of reactivity ratios such as: rM = 0.86 ± 0.1 and rS = 1.23 ± 0.09. Homopoly(LIMA) and copolymers with styrene were characterized as regards to average composition and molecular weight. Comb-like polymers were examined by X-ray analysis in the solid state; they were found to exhibit lamellar liquid-crystalline structures (smectic) resulting from the superposition of hydrophilic and hydrophobic layers.