Compositions – Liquid crystal compositions
Patent
1994-04-11
1996-07-02
Wu, Shean C.
Compositions
Liquid crystal compositions
428 1, 428402, 424450, 424455, 252302, 514937, 514964, C09K 1900, A61K 966, B01J 1300
Patent
active
055319254
DESCRIPTION:
BRIEF SUMMARY
This is a application of PCT/SE92/00692 filed under 35 USC 371, which is a continuation of U.S. application Ser. No. 07/771,014 now abandoned.
1. FIELD OF THE INVENTION
The present invention relates to the field of amphiphilic-solvent based systems and more specifically To the fragmentation of such systems by means of a novel method. Thus, by means of said novel method systems, which are otherwise homogeneous and in equilibrum, can be fragmented into small particles, especially colloidal particles. These new particles are extremely well suited as e.g. drug delivery particles or systems, but are also useful for several other medical as well as non-medical applications. Thus, the invention also encompasses said new particles as well as valuable uses thereof.
2. BACKGROUND OF THE INVENTION
The use of reversed cubic and liquid crystalline phases in the field of controlled release devices is described in EPO 125 751 (Engstrom et al 1983). However, there are many applications where the use of a homogeneous phase is not manageable. By the present invention it has become possible to prepare particles, especially colloidal particles, of such phases or similar phases, viz by means of a new fragmentation technique. The importance of said new technique, and the new particles obtained thereby, can be better understood from the following brief review of the prior art concerning other Types of particles and homogeneous phases.
2.1. Dispersed lipid-based systems in pharmaceutical preparations
Essentially, there have To date been three major particulate colloidal lipid-water systems which have been considered as suitable for drug delivery, namely such based on the lamellar mesophase as liposomes, micellar-based phases including micelles, reversed micelles, and mixed micelles and various kinds of emulsions including microemulsions, as well as more novel carriers as ISCOM's (Morein 1988) (a general text concerning these systems is Pharmaceutical dosage forms, Disperse systems 1988). The latter system has been utilized for intravenous nutrition since the beginning of this century and as an adjuvant system known as the Freunds adjuvant. These are of oil-in-water (O/W) and water-in-oil (W/O) types, respectively. Liposomes have since their discovery been extensively investigated as drug delivery systems for various routes and drugs. The development of new colloidal drug carrier systems is a research area of intensive activity and it is likely that new systems, especially new emulsion based systems, will appear in the near future (cf. Weiner 1990a, 1990b). Lipid-based vehicles can take several different morphological forms such as normal and reversed micelles, microemulsions, liposomes including variants as unilamellar, multilamellar, etc., emulsions including various types as oil-in-water, water-in-oil, multiple emulsions, etc., suspensions, and solid crystalline. In addition so called niosomes formed from nonionic surfactants have been investigated as a drug vehicle. The use of these vehicles in the field of drug delivery and biotechnology is well documented (Mulley 1974, Davis et al. 1983, Gregoriadis 1988a, Liebermann et al 1989). Particularly in the field of drug delivery the use of lipid-based drug delivery systems, especially dispersed systems, has attained increasing interest as the pharmaceutical industry is developing more potent and specific--and thus more (cyto)toxic--drugs. This is because the vehicle can in principle reduce such toxic effects and/or side-effects, due to sustained release or increased site-specificity. The current invention is easily distinguished from these earlier lipid-water based systems, as follows:
The term liposomes is conceptually wrong in view of the current knowledge of polymorphism of lipids. Liposome means "lipid body" and has by many authorities in the field been defined as any structure with an enclosed volume that is composed of lipid bilayers (see eg. Tice and Tabibi 1992). This is not only very misleading but also conceptually wrong. Such a definition means that any dispersed l
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"Drug Delivery from Cubic and Other Lipid-Water Phases", Sven Engstrom, Lipid Technology, vol. 2, No. 2, pp. 42-45 (Apr. 1990).
Landh Tomas
Larsson Kare
GS Biochem AB
Wu Shean C.
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