Method for the preparation of microspheres which contain colloidal systems
First Claim
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1. A method for preparing microspheres encapsulating colloidal systems, which method comprises the steps of:
- a) providing an aqueous mixture of i) a first phase comprising a first water soluble crosslinkable polymer, ii) a second phase comprising a second water soluble polymer which is incompatible in solution with the polymer in said first phase, and iii) colloidal systems to be suspended in said first phase;
b) forming an emulsion of said first phase in said second phase;
c) forming microspheres in the emulsion by crosslinking at least part of said crosslinkable polymer, thus forming said microspheres encapsulating colloidal systems; and
d) recovering the microspheres;
wherein said colloidal systems are selected from the group consisting of liposomes, iscoms, polyplexes, lipoplexes, nanoparticles, solid lipid particles in the colloidal size range, emulsions, and combinations thereof.
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Abstract
The invention relates to a method for the preparation of microencapsulated colloidal systems such as liposomes, i.e., microspheres which comprise colloidal systems. These microencapsulated colloidal systems can be used as controlled release systems for the delivery of active ingredients in in vivo and in vitro applications. A method is provided in which the colloidal systems are added to a phase which comprises a water soluble crosslinkable polymer followed by formation of microspheres.
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29 Claims
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1. A method for preparing microspheres encapsulating colloidal systems, which method comprises the steps of:
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a) providing an aqueous mixture of i) a first phase comprising a first water soluble crosslinkable polymer, ii) a second phase comprising a second water soluble polymer which is incompatible in solution with the polymer in said first phase, and iii) colloidal systems to be suspended in said first phase;
b) forming an emulsion of said first phase in said second phase;
c) forming microspheres in the emulsion by crosslinking at least part of said crosslinkable polymer, thus forming said microspheres encapsulating colloidal systems; and
d) recovering the microspheres;
wherein said colloidal systems are selected from the group consisting of liposomes, iscoms, polyplexes, lipoplexes, nanoparticles, solid lipid particles in the colloidal size range, emulsions, and combinations thereof. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 12, 15, 16, 17, 18, 19, 20, 21, 22, 23)
(1) said first water-soluble polymer which is crosslinkable; (2) said second water-soluble polymer, and (3) water, wherein said ternary system is characterized by a phase diagram and wherein said ternary system forms one phase when composition of the ternary system is below the binodal in said phase diagram and forms two phases when the composition of the ternary system is above the binodal in said phase diagram, and wherein the composition of said ternary two phase system provided is above said binodal and is capable of forming a continuous phase and a discontinuous phase;
and wherein said emulsion comprises a continuous and discontinuous phase, wherein said first, crosslinkable, polymer is the discontinuous phase in said two-phase system and the second polymer is the continuous phase in said two-phase system, said two phase system having been obtained by adjusting the amounts of water, first polymer and second polymer so as to place the system above the binodal, and wherein said colloidal system is present in said two-phase system.
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18. The method of claim 1, wherein the degree of crosslinking and water content are adjusted so as to result in pore sizes in said microspheres which are equal to or less than the hydrodynamic diameter of the colloidal system, said pores thus entrapping said colloidal system.
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19. The method of claim 1, wherein said first crosslinkable polymer, when crosslinked, can be degraded by virtue of comprising bonds that are hydrolyzable under physiological conditions, and said degradation of the crosslinked polymer occurs through hydrolyzing said bonds.
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20. The method of claim 1, wherein said first crosslinkable polymer, when crosslinked, can be degraded by virtue of including, in said microspheres, at least one enzyme which degrades said polymer, and wherein said degradation of crosslinked polymer occurs through action of said enzyme on said polymer.
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21. The method of claim 20, wherein said first crosslinkable polymer is dextran or derivatized dextran and the enzyme which degrades the polymer is dextranase.
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22. The method of claim 1, wherein said crosslinking is formed by crosslinking methacrylate or a methacrylate derivative or by using isocyanate or through poly-N-isopropyl acrylamide.
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23. The method of claim 1, wherein step (d) is performed by filtration or centrifugation.
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9. Microspheres, at least 80 wt. % thereof having a particle diameter of between 100 nm and 100 μ
- m, which microspheres are comprised of a degradable crosslinked polymer which encapsulates colloidal systems wherein said colloidal systems are selected from the group consisting of liposomes, iscoms, polyplexes, lipoplexes, nanoparticles, solid lipid particles in the colloidal size range, emulsions, and combinations thereof.
- View Dependent Claims (10, 11, 13, 14, 24, 25, 26, 27, 28, 29)
Specification