Three-dimensional self-assembling of gold nanorods with controlled macroscopic shape and local smectic B order.

We describe a method of controlled evaporation on a textured substrate for self-assembling and shaping gold-nanorod-based materials. Tridimensional wall features are formed over areas as large as several square millimeters. Furthermore, analyses by small-angle X-ray scattering and scanning electron microscopy techniques demonstrate that colloids are locally ordered as a smectic B phase.

Crystallization of fluorescent quantum dots within a three-dimensional bio-organic template of actin filaments and lipid membranes.

Biological molecules and molecular self-assemblies are promising templates to organize well-defined inorganic nanostructures. We demonstrate the ability of a self-assembled three-dimensional crystal template of helical actin protein filaments and lipids bilayers to generate a hierarchical self-assembly of quantum dots. Functionnalized tricystein peptidic quantum dots (QDs) are incorporated during the dynamical self-assembly of this actin/lipid template resulting in the formation of crystalline fibers.

Stable functionalized PEGylated quantum dots micelles with a controlled stoichiometry.

Here we report the synthesis of monofunctional PEGylated amide ligands that were used to prepare bioactivable quantum dots of a 20 nm diameter with a controlled mean number of the covalently grafted ligands. They are stable in aqueous medium of high salinity including a large pH domain.

Imaging gap junctions with silica-coated upconversion nanoparticles.

Upconversion nanoparticles (UCN) that are excited in the near infrared (NIR) region were synthesized and modified to enable their application to biological systems for imaging. The UCN obtained are oleic acid capped and hence hydrophobic in nature. Since the particles were to be used for imaging cells, a surface modification to make them hydrophilic and biocompatible was performed.

Small and stable peptidic PEGylated quantum dots to target polyhistidine-tagged proteins with controlled stoichiometry.

The use of the semiconductor quantum dots (QD) as biolabels for both ensemble and single-molecule tracking requires the development of simple and versatile methods to target individual proteins in a controlled manner, ideally in living cells. To address this challenge, we have prepared small and stable QDs (QD-ND) using a surface coating based on a peptide sequence containing a tricysteine, poly(ethylene glycol) (PEG), and an aspartic acid ligand. These QDs, with a hydrodynamic diameter of 9 +/- 1.

Integrin reconstituted in GUVs: a biomimetic system to study initial steps of cell spreading.

A novel in vitro membrane system mimicking the first steps of integrin-mediated cell spreading has been developed and characterized. We have reconstituted the transmembrane alpha(IIb)beta(3) integrin into giant unilamellar vesicles (GUVs). The reconstitution process has been validated by analyzing protein incorporation and biological activity by checking the specific interaction of GUVs containing integrin with quantum dots (QD) or surfaces coated with the integrin receptor tri-peptide RGD.

High-affinity labeling and tracking of individual histidine-tagged proteins in live cells using Ni2+ tris-nitrilotriacetic acid quantum dot conjugates.

Investigation of many cellular processes using fluorescent quantum dots (QDs) is hindered by the nontrivial requirements for QD surface functionalization and targeting. To address these challenges, we designed, characterized and applied QD-trisNTA, which integrates tris-nitrilotriacetic acid, a small and high-affinity recognition unit for the ubiquitous polyhistidine protein tag. Using QD-trisNTA, we demonstrate two-color QD tracking of the type-1 interferon receptor subunits in live cells, potentially enabling direct visualization of protein-protein interactions at the single molecule level.

One-pot synthesis and characterizations of bi-functional phosphor-magnetic @SiO(2) nanoparticles: controlled and structured association of Mo(6) cluster units and gamma-Fe(2)O(3) nanocrystals.

Nanostructured silica coated bifunctional nanoparticles based on [Mo(6)Br(14)](2-) units as phosphorescent dye and magnetic gamma-Fe(2)O(3) nanocrystals were synthesized and characterized.

Interaction between water-soluble peptidic CdSe/ZnS nanocrystals and membranes: formation of hybrid vesicles and condensed lamellar phases.

Due to their tunable optical properties and their well-defined nanometric size, core/shell nanocrystals (quantum dots, QDs) are extensively used for the design of biomarkers as well as for the preparation of nanostructured hybrid materials. It is thus of great interest to understand their interaction with soft lipidic membranes. Here we present the synthesis of water-soluble peptide CdSe/ZnS QDs and their interaction with the fluid lipidic membrane of vesicles.

Hierarchical architectures by synergy between dynamical template self-assembly and biomineralization.

Diatoms, shells, bones and teeth are exquisite examples of well-defined structures, arranged from nanometre to macroscopic length scale, produced by natural biomineralization using organic templates to control the growth of the inorganic phase. Although strategies mimicking Nature have partially succeeded in synthesizing human-designed bio-inorganic composite materials, our limited understanding of fundamental mechanisms has so far kept the level of hierarchical complexity found in biological organisms out of the chemists' reach. In this letter, we report on the synthesis of unprecedented double-walled silica nanotubes with monodisperse diameters that self-organize into highly ordered centimetre-sized fibres.

Time scales of membrane fusion revealed by direct imaging of vesicle fusion with high temporal resolution.

Membrane fusion is a vital process of life involved, for example, in cellular secretion via exocytosis, signaling between nerve cells, and virus infection. In both the life sciences and bioengineering, controlled membrane fusion has many possible applications, such as drug delivery, gene transfer, chemical microreactors, or synthesis of nanomaterials. Until now, the fusion dynamics has been elusive because direct observations have been limited to time scales that exceed several milliseconds.

Shear-induced permeation and fusion of lipid vesicles.

This paper introduces a novel approach to controlling membrane permeability in free unilamellar vesicles using shearing in the presence of a detergent with a large head-group to tune pore formation. Such shear-induced permeation could offer a simple means of postencapsulating bioactive molecules to prepare vesicle vectors for drug delivery. Using UV absorption, fluorescence emission, dynamic light scattering, and electron microscopy, we investigated the membrane permeability and the morphology of unilamellar lipid vesicles (diameter in the range 50-400 nm) subjected to a shear stress in the presence of a small amount of nonionic surfactant (Brij 76).

Fusogenic supramolecular vesicle systems induced by metal ion binding to amphiphilic ligands.

The incorporation of lipophilic ligands into the bilayer membrane of vesicles offers the possibility to induce, upon binding of suitable metal ions, a variety of processes, in particular vesicle aggregation and fusion and generation of vesicle arrays, under the control of specific metal-ligand recognition events. Synthetic bipyridine lipoligands Bn bearing a bipyridine unit as head group were prepared and incorporated into large unilamellar vesicles. The addition of Ni2+ or Co2+ metal ions led to the formation of complexes MBn and MBn2 followed by spontaneous fusion to generate giant multilamellar vesicles.

Selective complexation and transport of europium ions at the interface of vesicles.

The aim of the present work was to design functionalized lipidic membranes that can selectively interact with lanthanide ions at the interface and to exploit the interaction between membranes induced by this molecular-recognition process with a view to building up self-assembled vesicles or controlling the permeability of the membrane to lanthanide ions. Amphiphilic molecules bearing a beta-diketone unit as head group were synthesized and incorporated into phospholipidic vesicles. Binding of Eu(III) ions to the amphiphilic ligand can lead to formation of a complex involving ligands of the same vesicle membrane (intravesicular complex) or of two different vesicles (intervesicular complex).

Synthesis and properties of water-soluble gold colloids covalently derivatized with neutral polymer monolayers.

Citrate-capped gold nanoparticles as well as planar gold surfaces can be efficiently grafted with a covalently attached polymer monolayer a few nanometers thick, by simple contact of the metal surface with dilute aqueous solutions of hydrophilic polymers that are end-capped with disulfide moieties, as shown by UV/vis absorption, dynamic light scattering, and surface plasmon resonance studies. The hydrophilic polymer-coated gold colloids can be freeze-dried and stored as powders that can be subsequently dissolved to yield stable aqueous dispersions, even at very large concentrations. They allow for applying filtrations, gel permeation chromatography, or centrifugation.