Drug – bio-affecting and body treating compositions – Preparations characterized by special physical form – Liposomes
Patent
1987-06-29
1990-06-05
Bell, Mark L.
Drug, bio-affecting and body treating compositions
Preparations characterized by special physical form
Liposomes
264 41, 264 46, 424451, 4284022, 42840224, 514962, 514963, A61K 3720, A61K 952
Patent
active
049312847
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to the field of micro-encapsulation, i.e. the technique by means of which a substance that is intended to be protected from the surrounding or contact with another substance, is encapsulated in a surrounding protecting or contact-preventing envelope or shell. In this context the primary novelty is that it has turned out possible to encapsulate a hydrophobic or lipophilic substance within a crystalline shell of surface active crystals of polar lipids, which as far as we know of has not been previously used and means essential advantages as compared to known micro-encapsulation methods. In addition to an improved effect in several aspects relative to the prior art the invention also opens up possibilities for completely new application areas for micro-capsules, among which the use in ointment bases can be mentioned. More specifically the invention relates to novel micro-capsules, to an especially preferable micro-capsule composition containting said micro-capsules, to a process for the preparation of the micro-capsules or the micro-capsule composition as well as to a novel use of said micro-capsules. Furthermore, according to still another aspect the invention relates to a novel crystal dispersion and a method of preparing the same.
BACKGROUND OF THE INVENTION
Micro-capsules and micro-encapsulation are terms which are well known per se to a person skilled in the art, which means that there should be needed no definitions of said terms here. It is true that the meaning of the terms "micro" may possibly vary from one application area to another, but since the invention is not directly critical in this aspect, i.e. that a very specific size is necessarily referred to, that term should be considered in the present case merely as the conventionally accepted meaning of particles which are not macro particles of the sizes of several millimeters and thereabove. However, the especially preferable micro-encapsulation technique that is claimed generally gives particles having a size below 1 mm, which means that such particles are generally referred to in connection with the present invention.
Especially within the pharmaceutical and food industries there is today a great interest in encapsulating substances for the purpose of reducing the contacts with the surroundings. There are several known methods of performing a micro-encapsulation, such as e.g. a so-called complex coacervation in an aqueous medium, a phase separation, a polymerization in situ and a coating operation. The protective layer or shell is primarily built up from polymers, synthetic or native ones, or from amorphous lipids. For a survey of these different methods reference is made to Biomedical applications of micro-encapsulation; Lim, Franklin; CRC Press (1984). However, said known methods are connected with disadvantages of different kinds. Thus, it may for instance be that the manufacture is performed in the presence of non-physiological or toxic reagents or that the obtained structure is non-stable or non-reproducible.
SUMMARY OF THE INVENTION
The above-mentioned deficiencies and disadvantages are eliminated or at least reduced by means of the present invention. This is primarily accomplished by the use of a completely new type of shell in these connections, viz. a solid crystalline shell from surface active lipids, wherein these expose their hydrophilic face outwardly and their hydrophobic face inwardly towards the hydrophobic or lipophilic substance to be encapsulated. In other words the micro-capsules according to the invention possess a hydrophilic outer surface while at the same time they enclose a hydrophobic or lipophilic substance.
Thus, the characteristic features of the micro-capsules according to the invention are that the substance is a hydrophobic or lipophilic substance and that it is surrounded by surface active solid crystals of polar lipids, i.e. having one hydrophilic and one hydrophobic side or face, said lipids exposing their hydrophilic face outwards and their hydrophobic face
Ekman Bo M.
Larsson Kare V.
Lindahl Ake R.
Rothman Ulf S. E.
Bell Mark L.
Biogram AB
Green Anthony J.
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