Christophe Olivier

Cellulose Nanocrystal-Assisted Dispersion of Luminescent Single- Walled Carbon Nanotubes for Layer-by-Layer Assembled Hybrid Thin Films

Highly stable single-walled carbon nanotube (SWNT) dispersions are obtained after ultrasonication in cellulose nanocrystal (CN) aqueous colloidal suspensions. Mild dispersion conditions were applied to preserve the SWNT length in order to facilitate the identification of hybrid objects. This led to a moderate dispersion of 24% of the SWNTs. Under these conditions, atomic force microscopy (AFM) and transmission electron microscopy (TEM) experiments succeeded in demonstrating the formation of hybrid particles in which CNs are aligned along the nanotube axis by a self-assembly process. These SWNT/CN dispersions are used to create multilayered thin films with the layer-by-layer method using polyallylamine hydrochloride as a polyelectrolyte. Homogeneous films from one to eight bilayers are obtained with an average bilayer thickness of 17 nm. The presence of SWNTs in each bilayer is attested to by characteristic Raman signals. It should be noted that these films exhibit a near-infrared luminescence signal due to isolated and well-separated nanotubes. Furthermore, scanning electron microscopy (SEM) suggests that the SWNT network is percolating through the film.

Combined nanogap nanoparticles nanosensor for electrical detection of biomolecular interactions between polypeptides

A concept for the electrical detection of a biological interaction is proposed, mainly based on the conductance variation of a nanometer size-gap (typically less than 100 nm) between two planar electrodes. A functionalized surface was used in the vicinity of the gap in order to concentrate the ligand/receptor complex between the electrodes. The chemistry chosen for the immobilization of the ligand on the biosensor surface is compatible with peptide structures. The receptor in solution was labeled with gold particles which can be inserted into the gap. A significant conductance variation was observed without having to use a silver enhancer solution in the case of biotin/streptavidin or biotin/antibiotin antibodies model ligand/receptor interactions.

Synthesis of oligonucleotide–peptide conjugates using hydrazone chemical ligation

An oligonucleotide was functionalized on the solid-phase by a tartaramide moiety, which could be converted efficiently in solution into a glyoxylyl group following a mild periodic oxidation. The glyoxylyl-oligonucleotide was found to be very stable upon storage and was successfully engaged in hydrazone ligation with an α-hydrazino acetyl peptide.

Chemical Micropatterning of Polycarbonate for Site-Specific Peptide Immobilization and Biomolecular Interactions

Polycarbonate (PC) is a useful substrate for the preparation of microfluidic devices. Recently, its utility in bioanalysis has attracted much attention owing to the possibility of using compact discs as platforms for the high‐throughput analysis of biomolecular interactions. In this article we report a novel method for the chemical micropatterning of polycarbonate based on the printing of functionalized silica nanoparticles. The semicarbazide groups present on the surface of the nanoparticles were used for the site‐specific semicarbazone ligation of unprotected peptides derivatized by an α‐oxoaldehyde group. The peptide micropatterns permitted the specific capture of antibodies. We report also the characterization of micropatterns on PC by using a wide‐field optical imaging technique called Sarfus; this allows the detection of nm‐thick films by using nonreflecting PC substrates and an optical microscope working with reflected differential interference contrast. The method described here is an easy way to modify polycarbonate surfaces for biomolecular interaction studies and should stimulate the use of PC for developing plastic biosensors.

Preparation of α‐Oxo Semicarbazone Oligonucleotide Microarrays

This unit describes the preparation of α‐oxo aldehyde functionalized oligodeoxynucleotides, the preparation and characterization of semicarbazide glass slides, and the fabrication of α‐oxo semicarbazone microarrays by site‐specific ligation of α‐oxo‐aldehyde oligodeoxynucleotides to the semicarbazide glass slides. The α‐oxo aldehyde group COCHO is extensively used in ligation chemistry for the preparation of large molecular constructs. It is stable toward air oxidation and mainly present in aqueous solution in the hydrated form COC(OH)2. It reacts efficiently with hydrazine derivatives, in particular, with the semicarbazide group. The reaction occurs spontaneously in water at pH 5.5. Site‐specific immobilization of glyoxylyl oligodeoxynucleotides on semicarbazide glass slides allows the preparation of high‐quality microarrays that can be used directly in hybridization experiments.