Water dynamics in silanized hydroxypropyl methylcellulose based hydrogels designed for tissue engineering.

Silanized hydroxypropyl methylcellulose based hydrogels were developed for cartilage and intervertebral disc tissue engineering. Herein, study of dynamics of confined water showed two different populations, identified as hydration and bulk-like water. The diffusion coefficient showed that bulk-like water diffuses over distances ∼10 µm without being affected by the hydrogel matrix. Addition of silica nanofibers leads to improved mechanical properties and enhanced diffusion coefficient. Good diffusion within hydrogels is essential for the application.

Carboxymethylcellulose/single walled carbon nanotube complexes.

In this work, Carboxymethylcellulose/single walled carbon nanotube hybrids are prepared. Our goal is to use the non-covalent association of an anionic polysaccharide and single walled carbon nanotubes to prepare a biocompatible complex which preserves the intrinsic properties of the nanotubes. The hybrids are characterized by Raman scattering, Emission spectroscopy and Atomic Force Microscopy. A comparison is made with sodium dodecyl benzene sulfonate dispersed nanotubes. We show that carboxymethylcellulose forms an apparently non-helicoidal superstructure with carbon nanotubes which leads to their individualization. Emission and Raman spectroscopies suggest that the interaction occurs preferentially with semiconducting nanotubes. Further sugar chemistry may open different functionalization opportunities that will contribute to the design of biosensors and open this field of applications.

Photophysical comparative study of amylose and polyvinyle pyrrolidone/single walled carbon nanotubes complex.

Progressive addition of hydroxypropylated amylose (AmH), from 0.05 wt% to 4.5 wt%, to single-walled carbon nanotubes (SWNTs) in aqueous surfactant suspensions quenches the intrinsic near Infra-Red fluorescence of semiconducting SWNTs while dispersions obtained with a same amount of polyvinylpyrrolidone (PVP) remain luminescent. Near Infra-Red emission spectroscopy (fluorescence and Raman scattering) of the samples is used to characterize the supramolecular organization of these polymer/SWNT complexes. The SWNTs are found to be wrapped by the PVP chains and not by the AmH chains which rather form AmH/surfactant/SWNTs complexes. In PVP/SWNTs dispersion, the fluorescence line position and intensity are affected by dielectric screening. In the case of AmH/surfactant/SWNTs complex, dielectric screening plays also a role but quenching occurs above about 3 wt% of AmH. We attribute the quenching to the formation of a "composite like" microstructure by opposition to stabilized dispersion.

Coaxial nickel/poly(p-phenylene vinylene) nanowires as luminescent building blocks manipulated magnetically.

A template-based strategy was developed which combines a wet-chemical technique and electrodeposition within nanoporous membranes. Morphological, structural and chemical characterization by means of electron microscopy and related techniques demonstrate unambiguously that coaxial nickel/poly(p-phenylene vinylene) (PPV) nanowires have been successfully synthesized. Moreover, modification of their optical and magnetic properties due to the nanoscale and the core-shell structure has been studied. The nickel-PPV nanowires exhibit a slightly blueshifted photoluminescence (PL), which is directly related to the tubular morphology of the PPV shell. The effect of the nickel core on the PL intensity of the PPV shell is discussed. The ferromagnetic behavior has been shown with the magnetization easy axis along the wire axis. These arrays of coaxial semiconducting polymer-metal nanowires embedded in a polymer membrane are interesting for flexible electronics and photovoltaic devices. Furthermore, their magnetic manipulation has been demonstrated, which opens the way to use them as multifunctional building blocks for bio-applications.

[Maternal toxoplasmosis before conception and chorioretinitis in twin sisters]. / Toxoplasmose maternelle anté-conceptionnelle et choriorétinite chez des jumelles.

A maternal toxoplasmosis before conception is exceptionally transmitted to the fetus. We report an observation of twin sisters who presented congenital toxoplasmosis with chorioretinitis detected at nine months of age. The anamnesis revealed that the mother had had toxoplasmosis one month before conception. In the event of preconceptual infections, we propose fetal ultrasonography, histological examination of the placenta at delivery, as well as a pediatric follow-up of the infants (serological samples every month, cranial ultrasonography, fundus oculi).

Microwave single walled carbon nanotubes purification.

A new single walled carbon nanotubes (SWCNTs) purification procedure has been developed; it consists in a combination of air treatment and acid microwave digestion leading to a high purity SWCNTs material; the procedure reaches high metal removal percentages and the operation time is drastically reduced compared to conventional acid reflux treatments.

On the origin of the square root of (7) x square root of (7) superstructure and the anomalous magnetic and transport properties of the layered compound Sr(6)V(9)S(22)O(2).

We examined why the 1T-VS(2) layer of the layered compound Sr(6)V(9)S(22)O(2) has the x superstructure in terms of electronic band structure calculations and metal-metal bonding across the shared edges of adjacent VS(6) octahedra. On the basis of this analysis we explored how the anomalous magnetic and transport properties of Sr(6)V(9)S(22)O(2) can be explained. Our work shows that the x superstructure is not caused by a charge density wave instability associated with Fermi surface nesting but by the metal-metal bonding through the shared edges of adjacent VS(6) octahedra. The weak and strong electron localizations observed for Sr(6)V(9)S(22)O(2) were discussed in terms of three-center two-electron and two-center two-electron V-V bonds in the 1T-VS(2) layers.

Single-Crystalline (KC60)n: A Conducting Linear Alkali Fulleride Polymer.

Single crystals of a linear cycloadduct conducting polymer, (KC(60))n, have been grown that are a few tenths of a millimeter in length. Partial oxidation under toluene transformed these crystals into bundles of fibers. The degree of polymerization exceeded 100,000.