Stabilization of colloidal systems through the formation of lipi

Details Stabilization of colloidal systems through the formation of lipi Stabilization of colloidal systems through the formation of lipi

1997-02-27

1998-12-01

Kishore, Gollamudi S.

Drug, bio-affecting and body treating compositions

Preparations characterized by special physical form

Particulate form

424490, 424491, 424493, 424497, 424498, 514937, 514963, A61K 916, A61K 914

Patent

active

058435093

DESCRIPTION:

BRIEF SUMMARY
This application is a 371 of PCT/ES96/00116 filed May 24, 1996.
This invention relates to stabilization of colloidal systems through the formation of lipid-polyssacharide complexes and development of a procedure for the preparation of colloidal systems involving a combination of two ingredients: a water soluble and positively charged polyssacharide and a negatively charged phospholipid. The procedure can be applied to the stabilization of colloidal systems of pharmaceutical and cosmetic use. These systems include oil-in-water submicron emulsions, nanocapsules consisting of an oily core surrounded by a polymer coating and polymeric solid nanoparticles. The common feature to all these colloidal systems is that they consist of a dispersed phase--oily nanodroplets, nanocapsules or nanoparticles--and a continuous aqueous phase. The originality of the procedure relies on the incorporation of lecithin (anionic ingredient), as a lipophilic surfactant, in the dispersed phase and of the chitosan, as a hydrophilic suspending agent, in the continuous aqueous phase.
Lecithin is a natural surfactant composed of a mixture of various phospholipids. The major compound is phosphatidylcholine (a phospholipid of a neutral character) and the secondary compounds are phosphatidylethanolamine, phosphatidylserine and phosphatidic acid (phospholipids with a negative charge). Presently, there are several types of lecithin available in the market. They differ in their origin and in their phosphatidylcholine content.
Chitosan is a natural polymer obtained by a deacetatilation process of the chitin (compound extracted from the crustacean shells). Chitosan is an aminopolyssachride and has a positive charge. Presently, there are several types of chitosan available in the market. They differ in their molecular weight, deacetilation degree and the type of salt or acid form.
The colloidal systems of the invention are characterized by having contain lecithin and chitosan in their composition and they have a positive charge and an improved stability. Other ingredients will be specific to the type of system i.e. an oil, in the case of the submicron emulsions; an oil and a hydrophobic polymer, in the case of the nanocapsules, and a hydrophobic polymer in the case of the nanoparticles. Drugs, proteins and other bioactive compounds of interest in medicine and cosmetics can be incorporated in these systems. Consequently, the application of these systems could be extended to the fields of medicine and cosmetics.
A important draw back of the colloidal carriers is their unstability following in vivo administration and also during storage. It is well known that the majority of the colloidal carriers have a negative surface charge and, because of this fact, they interact with the cationic biologic compounds upon in vivo administration, thus leading to coalesce and destruction of the system. Difficulties in the freeze-drying process, more specifically problems in the reconstitution of the freeze-dried systems, represent another important limitation for the correct exploitation of the colloidal systems specially the nanocapsules and submicron emulsions. As a consequence, these systems have to be stored as a suspension liquid form, a situation that normally leads to the destruction of the systems in a few months. The novel systems presented here have a positive charge and an improved stability upon contact with biological cations and during storage. Consequently, these systems overcome the limitations mentioned above.
There are in the literature a large number of publications and patents describing procedures to produce colloidal systems such as nanoparticles, nanocapsules and submicron emulsions. Therefore, the production of these systems is not the object of the present invention. The object is, however, the incorporation in such colloidal systems of two specific ingredients: lecithin and chitosan. The preparation of these systems involves the use of two phases: an oily phase that is dispersed in an aqueous phase. Both phases normally contain surfactant

REFERENCES:
patent: 5536508 (1996-07-01), Canal et al.
P. Faldt, et al., "Stabilization by chitosan of soybean oil emulsions coated with phospholipid and glycocholic acid", Colloids Surfaces A: Physicochem. Eng. Aspects, 71, 187-195, 1993.
I. Henriksen, et al., "Interactions between liposomes and chitosan", Int. J. Pharm., 101, 227-236, 1994.
Faldt, P. et al. "Stabilizatoin by chitosan of soybean oil emulsions coated with phospholipid and glycocholic acid" (1993) Colloids and Surfaces A: Physicochemical and Engineering Aspects, vol. 71, pp.: 187-195, complete document.

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