Drug – bio-affecting and body treating compositions – Preparations characterized by special physical form – Liposomes
Patent
1996-12-13
1999-08-31
Kishore, Gollamudi S.
Drug, bio-affecting and body treating compositions
Preparations characterized by special physical form
Liposomes
424489, 424490, 424491, 424492, 424493, 424497, A61K 9127, A61K 916
Patent
active
059451203
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to gelified microspheres, to their method of preparation and to their applications.
2. Discussion of the Background
Microspheres, which are particles of spherical shape, the size of which ranges, generally, between 1 and 1250 .mu.m, are composed of a support material containing the encapsulated substance and are of particular advantage, either when it is desirable to administer a medicament in a form which makes possible the controlled release of the active component over a certain period, in order to provide for a prolonged pharmacological effect, or when it is necessary to protect the said active component from premature degradation in the digestive tract.
Depending on the structure of the support material, two types of microcapsules are distinguished: envelope of variable thickness containing the substance to be encapsulated, support material is a continuous network in which the substance to be encapsulated is dispersed.
Within the meaning of the present invention, the term microcapsule or microsphere comprises only microcapsules or microspheres of matrix type.
Many substances can be encapsulated: it can relate to chemicals, such as medicaments, or alternatively to macromolecules, such as enzymes, and also to living cells.
Microspheres are used in many fields, such as pharmaceuticals, the biotechnology industry, cosmetology, the agri-foodstuffs industry, the paper-manufacturing industry, and the like.
A number of methods for the preparation of microcapsules have been described; mention may in particular be made of: 4,675,189 and Application EP 52,510, which describes microcapsules prepared by a phase-separation technique using a coacervation agent, such as mineral oils or vegetable oils.
However, the microcapsules prepared by this method and by other analogous methods have the disadvantage of forming clusters (inter-adhesion of particles) during the preparation of the said microcapsules. 4,479,911, Application EP 301,969 and Application EP 145,240; this method comprises the separate formation water-immiscible solvent and two phases with agitation and/or in the presence of an emulsifying agent and then the evaporation of the solvent, generally with agitation and at room temperature, in order to obtain the desired microcapsules.
Application EP 145,240 more particularly describes microcapsules produced by preparing a W/O emulsion (primary emulsion) comprising an inner aqueous layer containing a hydrophilic substance and a so-called medicament-retention substance (natural or synthetic mucilage or high-moleculer-weight compounds and more particularly gelatin) and an oily layer containing a polymer, preferably a polylactic acid or a copolymer of lactic acid and of glycolic acid or their mixtures, in a water-immiscible solvent such as dichloromethane, by then thickening or solidifying the said inner aqueous layer so as to obtain a viscosity greater than 5,000 centipoises, by then preparing a secondary W/O/W emulsion in the presence of a suitable surface-active agent and, finally, by subjecting the emulsion thus obtained to evaporation of the solvent. The process described in this Application makes it possible to obtain microcapsules with a diameter of between 0.5 and 400 .mu.m.
However, these microcapsules or microspheres of the prior art have the major disadvantage of having diameters of the order of a .mu.m or more (1-1250 .mu.m); now, there exist many applications for which it is necessary and/or particularly advantageous to be able to have available particles having a significantly smaller diameter, in particular of the order of an nm or more, for example between 20 and 600 nm.
SUMMARY OF THE INVENTION
The Applicants have consequently devoted themselves to the goal of developing gelified microspheres, the diameter of which can be controlled and can reach, if necessary, 20 nm.
The subject of the present invention is microspheres, characterized in that they comprise a gelified polar core (GPC) around which are superimpose
REFERENCES:
patent: 4708861 (1987-11-01), Popecu
patent: 5008109 (1991-04-01), Tin
Hauton, deceased Jacques
Salles Jean-Pierre
Kishore Gollamudi S.
Lipogel
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