Multilamellar vesicles called Spherulites have recently been discovered and are being developed for encapsulation applications. In this study, we present new systems of Spherulites called complex dispersions. These are prepared by dispersing Spherulites within an oily medium, and then emulsifying this oily dispersion of Spherulites within an aqueous solvent. The ability of complex dispersions to reduce the release of encapsulated ions under variable osmotic dilutions was evaluated and compared with Spherulites directly dispersible in an aqueous medium, and with multiple emulsions. An advantage of complex dispersions over Spherulites is to present an additional oily barrier. Indeed, this barrier retarded the release of encapsulated ions. Complex dispersions also proved to be less sensitive to osmotic pressure than multiple emulsions. It appeared that the dilution of a complex dispersion formulated with no external aqueous phase containing a hydrophilic surfactant provided the slowest release of encapsulated ions. Furthermore, this formulation maintained a difference of pH between the internal and external aqueous phases for a few hours. In conclusion, these new systems of Spherulites known as complex dispersions show great potential for pharmaceutical applications such as controlled release and protection of encapsulated substances.

Spherulites® are multilamellar vesicles made up of surfactant bilayers. These vesicles would potentially be very useful for the encapsulation and protection of molecules; however, traditional formulations of these vesicles are poor at retaining small hydrophilic molecules (below 1000 g/mol). In this study, we present new systems of Spherulites called complex dispersions. These are prepared by dispersing Spherulites in an oil medium, and then emulsifying this oily dispersion of Spherulites within an aqueous solvent. These new systems provide an additional oil barrier between encapsulated molecules and an external aqueous phase. We have used polarized light optical microscopy, X-ray diffraction and freeze–fracture electron microscopy to study a complex dispersion of Spherulites at all stages of its preparation. We first studied the sheared lamellar phase, followed by the dispersion of the multilamellar vesicles in the oily medium and finally the emulsification of the oily dispersion within the aqueous solvent. We compared our results on lamellar phases with previous results obtained with Spherulites directly dispersible in an aqueous medium. Since the formulation of our lamellar phase included a large percentage of oil as a component, we studied the localization of the oil in the lamellar structure. We also studied the influence of osmotic pressure on complex dispersions, because complex dispersions possess a double structure similar to that of water-in-oil-in-water emulsions and multiple emulsions are known to be sensitive to osmotic pressure. In conclusion, complex dispersions proved to be new potential carriers exhibiting some unique physical properties.

Concentric multilamellar microvesicles, named spherulites(TM), were evaluated as an oligonucleotide carrier. Up to 80% oligonucleotide was encapsulated in these vesicles. The study was carried out on two different spherulite(TM) formulations. The spherulite(TM) size and stability characteristics are presented. Delivery of encapsulated oligonucleotide was performed on a rat hepatocarcinoma and on a lymphoblastoid T cell line, both expressing the luciferase gene. We showed that spherulites(TM) were able to transfect both adherent and suspension cell lines and deliver the oligonucleotide to the nucleus. Moreover, 48-62% luciferase inhibition was obtained in the rat hepatocarcinoma cell line when the antisense oligonucleotide targeted to the luciferase coding region was encapsulated at 500 nM concentration in spherulites(TM) of different compositions.

The invention concerns an improved method for avoiding the degradation of an active principle. The invention is characterised in that the active principle is incorporated inside multilamellar vesicles with an onion-like structure and consisting, from the periphery towards the centre, concentric membranes in the form of double layers comprising at least a surfactant, said membranes being separated by an interstitial liquid, said vesicles containing at least an agent for avoiding degradation of said active principle. The invention is more particularly applicable to the stabilisation of products sensitive to oxidation, reduction or hydrolysis and to products sensitive to more specific degradation reactions such as enzymes. The invention also concerns compositions containing said multilamellar vesicles and their method of preparation.

It has been shown recently that shearing of lyotropic lamellar phases may lead to the formation of relatively monodispersed multilayered vesicles named spherulites. Freeze−fracture electron microscopy analysis of such preparations, presented here, shows that their three-dimensional organization is of a space-filling polyhedral type, built up from very closely packed spherulites, without any visible additional water present neither in the center of the spherulites nor in between them. Dilution of these preparations leads to the separation of individual spherulites without appreciable changes of their internal structure (multilayered nature and spacing between the layers). Diluted spherulites become spherical and are separated by the water dispersions of much smaller vesicles, originating probably from the fragmentation of some external layers of concentrated spherulites.

A method for the coupling of polyacrylamide beads to polyethylene terephthalate (PET) vascular prostheses is described. The reactional procedure used is performed along several steps; acrylic acid grafting on PET textile fibres, in order to introduce reactive carboxylic groups, introduction of terminal primary amine groups onto the beads, and then, attachment method which consists in coupling carboxylic groups of prostheses with amine groups of modified beads. The relative weight increase of the samples before and after the coupling reaction and, microscopic observations of beads distribution onto the prostheses surface demonstrate the binding feasibility of polyacrylamide matrices to PET prostheses. In the near future, authors expect to replace these beads by microcapsules with polyacrylamide wall and containing active compounds to improve the vascular prostheses biocompatibility.

A new series of mesomorphic side chain polysiloxane networks has been recently synthesized in which the chemical nature of the linkage and the mesogenic group have been varied and the gelation conditions during the chemical reaction have been studied. This paper presents an X-ray diffraction study of the mesogenic group orientation in stretched samples of these networks. The angular extension of the so-called wide angle diffuse ring is used to estimate the orientational order of the mesogenic group versus strain. To perform these experiments, a special stretching device was developed and a new two-dimensional X-ray detector was used which allowed us to collect the data in a few minutes. On stretching, it was observed that the mesogenic groups orient themselves perpendicular to the stress direction for all of the samples but for one for which the parallel orientation prevailed. This prevents the establishment of a simple general law. From another point of view, the polymer concentration during the chemical reaction, which controls the gelation, is shown to be an important parameter with which to understand the physical properties: the networks synthesized below the gel point do not display reproducible and reversible behaviour, rather they flow when they are stretched. Conversely, all of the networks synthesized above the gel point really show the same well-defined behaviour independent of the sample history. Their orientational order increases regularly with the strain, first quickly, then moderately until it eventually saturates. This saturation value' of the mesogenic group orientational order does not reach the nematic order parameter of the same (uncross-linked) mesomorphic side chain polymers. This suggests that the cross-links may create local tensions which disturb the nematic field.

Abstract A series of crosslinked liquid crystalline polysiloxanes has been realized by successively modifying the crosslinking density, the chemical nature of the linkage and the nematogenic or smectogenic character of the mesogen. All these parameters affect the polymorphism of the network, especially the ordered smectic A phases which have been proved more sensitive to crosslinking than the nematic phases. The mechanical measurements confirm the influence of the structure of the material and show that, in the smectic state, the mesogenic side groups build up ordered structures which create much more important retractive forces than in a purely nematic material.