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The interaction between phosphatidylinositol 4,5-biphosphate (PI[P.sub.2]) and ezrin is examined in vitro by using Pi[P.sub.2] dispersed in a unimolecular way in buffer. The studies have shown that PI[P.sub.2] has induced a conformational change in full-length ezrin and has played a role in the formation of ezrin oligomers.

A series of biodegradable alkylamino hydrazide hyaluronic acid (HA) derivatives were prepared and used to design new biocompatible films able to release hydrophobic drugs in a controlled manner. The first step of this work thus consisted in optimizing the synthetic conditions of hydrazide HA derivatives bearing pendant hexyl, octyl, decyl, and citronellyl chains with a degree of substitution of 0.05 or 0.10. The behavior in aqueous solution of these water-soluble modified HA samples was then examined in the semidilute regime. The decylamino hydrazide derivatives of HA exhibited remarkable associating properties, giving rise to transparent gels. These gels were found to be more resistant to degradation by hyaluronidase compared to solutions of nonmodified HA at the same concentration. The other derivatives of which the lengths of grafted alkyl chains range from 6 to 8 carbon atoms lead to more or less viscous solutions. Different viscometric features for these derivatives could be observed as a function of the molecular weight of HA. As derivatives prepared from a HA sample of 600,000 g/mol (HA-600) exhibited a much higher tendency to self-aggregate than their counterparts prepared from a HA sample of 200,000 g/mol (HA-200), the latter derivatives were selected for the build up of multilayer films. The topography and z-section of (PLL/HA derivatives) films assembled layer-by-layer were observed by atomic force microscopy (AFM) in liquid and confocal laser scanning microscopy (CLSM) using PLL(FITC) as ending layer. Moreover, the ability of the films made of the different HA derivatives to incorporate the hydrophobic dye nile red (NR) was investigated. Films containing decylamino hydrazide HA derivatives were the most efficient for incorporating and retaining nile red, which confirms the formation of stable hydrophobic nanodomains in the films.

We report on the preparation of polyelectrolyte films based on biopolymers whose nanomechanical properties can be tuned by photo-cross-linking. Cationic poly(L-lysine) was layer-by-layer assembled with anionic hyaluronan (HA) derivatives modified by photoreactive vinylbenzyl (VB) groups. The study of the multilayer buildup by quartz crystal microbalance with dissipation monitoring showed that the presence of VB groups does not influence significantly the multilayer growth. Then the VB-modified HA incorporated into the films was cross-linked upon UV irradiation. UV spectroscopy measurements showed that the cross-linking rate of the multilayers increases with the amount of VB groups grafted onto HA chains. Force measurements performed by atomic force microscopy with a colloidal probe proved that the rigidity of the cross-linked films increases with the grafting degree of HA chains and consequently the number of cross-links. Cell culture assays performed on non-cross-linked and photo-cross-linked films with myoblast cells demonstrated that cell adhesion and proliferation are considerably improved with increasing film rigidity.

The objective of this work was to investigate the formation of hollow microcapsules composed of hyaluronic acid (HA) and poly(allylamine) (PAH) by layer-by-layer adsorption on CaCO 3 microparticles and subsequent core removal by addition of chelating agents for calcium ions. We found that the molecular weight of HA as well as the HA solution concentration used during deposition are crucial parameters influencing the multilayer structure. Whereas the effect of molecular weight of HA was mainly attributed to the porous structure of the template which allows penetration of polyelectrolytes when their size is below the maximum pore size of the template ( approximately 60 nm), that of the concentration of the HA solution was related to the intrinsic properties of the polysaccharide. Indeed, as shown by quartz crystal microbalance with dissipation monitoring as well as electron microscopy techniques, the latter leads to dense structures for concentrations from five to ten times the critical overlap concentration during adsorption. Such conditions were found to be favorable for the formation of hollow shells. Regarding conditions for core dissolution, we demonstrated the possibility to use either ethylenediaminetetraacetic acid (EDTA) or citric acid as chelating agents. However, in some cases, it was necessary to chemically cross-link the shell to maintain its integrity.