Drug – bio-affecting and body treating compositions – Preparations characterized by special physical form – Particulate form
Reexamination Certificate
2000-10-26
2003-09-09
Page, Thurman K. (Department: 1615)
Drug, bio-affecting and body treating compositions
Preparations characterized by special physical form
Particulate form
C424S455000, C424S489000
Reexamination Certificate
active
06616947
ABSTRACT:
This application is a 371 of PCT/FR99/00280 filed Feb. 9, 1999.
A subject-matter of the present invention is a novel encapsulation system having an external surface which is essentially inorganic in nature, this surface being suited to the protection and/or to the controlled release of organic compound(s).
It is possible, among the encapsulation systems already available for the inclusion of organic substances, to distinguish two main types thereof:
the first system is similar to a so-called chamber system; the agent to be encapsulated is retained therein using a membrane which is conventionally polymeric in nature. These organic capsules are obtained by interfacial reaction. The size of the capsules is generally much greater than a micron;
the second system is a so-called matrix system; the agent to be encapsulated is dispersed therein in an organic network (polymer) or in a substance which is inorganic in nature (in particular silica). Mention may in particular be made, by way of illustration of this second system, of plant-protection formulations for the controlled release of insecticides with silica microcapsules (Zairyo Gijutsu, Vol. 5, No. 5 (1987) 231-236). These microcapsules of a few microns are prepared by precipitation of an alkaline silicate in the presence of a water-in-oil emulsion, the particles subsequently being calcined. The specific surfaces of the microcapsules are very high (of between 200 and 400 m
2
/g). The active principle is introduced by adsorption on the powder with a relatively low degree of adsorption, of the order of 10%.
A specific object of the present invention is to provide a novel encapsulation system which is particularly advantageous with regard to the systems mentioned above.
The encapsulation obtained according to the present invention has, as first advantage, the advantage of protecting the encapsulated active principles from the aggressiveness of the chemical environment by bio- or ecocompatible capsules. Finally, it has in particular the advantage of making possible their release, either by diffusion or by dissolution of the shell, under the effect of a change in pH.
More specifically, the claimed encapsulation system takes advantage of the ability of basic aluminium carbonate to only dissolve from a pH of less than 5. It thus guarantees, in any host medium with a pH greater than 5, an efficient encapsulation of the organosoluble compounds which it encapsulates. In addition, basic aluminium carbonate has the advantage of having a cationic charge, which can be adjusted according to the precipitation pH. It thus proves to be possible to adjust the interactions of charges between the core constituting the encapsulation system and its shell. This is of advantage in terms of limiting the agglomeration of the particles of the encapsulated system and of quality of deposition.
The encapsulation of these active principles is carried out according to the invention by in situ precipitation of basic aluminium carbonate, constituting in all or part the inorganic shell of the capsule, in the presence of the said active principle(s) to be encapsulated.
The problem more specifically posed and solved according to the present invention related to the formation of a capsule with a shell composed of basic aluminium carbonate, and thus inorganic in nature, about an essentially organic core. It was important to find an efficient surfactant system in order, if appropriate, to stabilize the formulation per se of the active principle present at the core of the capsule and, in particular, to make possible adhesion between the core which is organic in nature and the shell based on basic aluminium carbonate, which is inorganic in nature.
The use of a nonionic surfactant composed of at least one segment with a hydrophilic nature and of at least one segment with a hydrophobic nature has made it possible to satisfactorily respond to this twofold requirement.
Consequently, a first subject-matter of the present invention is an encapsulation system comprising an organic core and an inorganic shell, characterized in that:
the core is composed, in all or part, of at least one organic active principle,
the inorganic shell is composed, in all or part, of basic aluminium carbonate, and
in that the cohesion of the said encapsulation system is achieved with the help of at least one nonionic surfactant comprising at least one hydrophobic segment and at least one hydrophilic segment.
Within the meaning of the present invention, the definition “surfactant comprising hydrophobic segment(s) and hydrophilic segment(s)” is understood to cover any surfactant having either units or chains which are hydrophilic or hydrophobic in nature.
Mention may in particular be made, by way of illustration but without implied limitation of these surfactants, of the following compounds:
polyalkoxylated fatty alcohols, such as polyethoxylated fatty alcohols,
polyoxyalkylenated alkylphenols, such as di- or tristyrylphenols,
polyvinyl alcohols or polyvinyl alkyl ethers, and
block copolymers, such as polystyrene/poly(ethylene oxide).
As regards the degree of polymerization of the poly(alkylene oxide) segment present in some compounds identified above, it is generally between 2 and 50 mol and more preferably varies between 3 and 25 mol.
Preferably, this surfactant additionally has an HLB (Hydrophilic-Lipophilic Balance) value suitable for stabilizing, if appropriate, the emulsion or the dispersion of the encapsulated organic active principle(s). This HLB value is generally greater than 6 and preferably greater than 10.
More preferably, the nonionic surfactant under consideration according to the present invention is selected from polyalkoxylated alcohols, tristyrylphenols and block copolymers.
Mention will very particularly be made, by way of representation of the block copolymers which are suitable for the present invention, of the polystyrene/poly(ethylene oxide) copolymer sold under the name UPSE 1030® by the company Goldschmidt.
Among polyalkoxylated fatty alcohols, the polyethoxylated alcohol sold under the name Emulgapur LM7555® also leads to satisfactory results according to the invention.
This nonionic surfactant is generally present in the claimed encapsulation system in amounts sufficient to provide for the cohesion of the said system. It is preferably present in a proportion of approximately 1 to 3%, expressed by weight with respect to the organic components.
As regards the encapsulated active principle, it can be incorporated within the encapsulation system as is, that is to say in its native form, that is to say solid or liquid.
It is also possible to envisage incorporating it in the form of an aqueous emulsion. In this specific case, it is present in the non-continuous phase. This aqueous emulsion can be obtained in particular by incorporation of the pure active principle or of the active principle dissolved beforehand in an appropriate oil of silicone oil type, for example.
It is also possible to incorporate the active principle in the form of an aqueous dispersion.
The active principle, as is or dissolved beforehand in an oil, can generally be dispersed or emulsified at up to 70% by weight of the aqueous phase.
In both these cases, the organic active principle is preferably stabilized within the aqueous phase prior to the encapsulation.
As mentioned above, the active principle can be stabilized within the aqueous dispersion or emulsion by the nonionic surfactant according to the invention. However, it is also possible to envisage incorporating one or more other surfactants within the dispersion or emulsion.
These additional surfactants, of use in particular in dispersing, emulsifying, dissolving and/or stabilizing the various compounds to be encapsulated, can be anionic, nonionic, cationic, zwitterionic or amphoteric.
Mention may more particularly be made, by way of illustration of these compounds, of:
anionic surfactants, such as alkyl ester sulphonates, alkyl sulphates, alkylamide sulphates and the salts of saturated or unsaturated fatty acids;
nonionic surfactants, such as polyoxyalk
Bennett Rachel M.
Burns Doane Swecker & Mathis L.L.P.
Rhodia Chimie
LandOfFree
Encapsulation system with organic core and mineral cortex... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Encapsulation system with organic core and mineral cortex..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Encapsulation system with organic core and mineral cortex... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3037696