Method of preparing gas-filled microspheres using a lyophilized lipids

• US 5,776,429 A
• Filed: 04/30/1996
• Issued: 07/07/1998
• Est. Priority Date: 12/22/1989
• Status: Expired due to Term

• Current Assignee: Lantheus Medical Imaging, Inc. (Lantheus Holdings, Inc.)
• Original Assignee: Imarx Pharmaceutical Corp. (Sycamore Entertainment Group, Inc.)
• Inventors: Ramaswami, VaradaRajan, Yellowhair, David, Matsunaga, Terry, Fritz, Thomas A., Unger, Evan C., Wu, Guanli
• Primary Examiner(s): Hollinden, Gary E.
• Assistant Examiner(s): Hartley, Michael G.
• Application Number:
  US08/643,070
• Time in Patent Office: 798 Days
• Field of Search: 424/9.52, 424/9.5, 424/9.51, 424/450, 424/489, 424/498, 128/662.02
• US Class Current: 424/9.52
• CPC Class Codes: A61K 41/0028 Disruption, e.g. by heat or ultrasounds, sonophysical or sonochemical activation, e.g. thermosensitive or heat-sensitive liposomes, disruption of calculi with a medicinal preparation and ultrasounds
• CPC Class Codes: A61K 41/0052 Thermotherapy; Hyperthermia; Magnetic induction; Induction heating therapy
• CPC Class Codes: A61K 49/22 Echographic preparations; Ultrasound imaging preparations ; Optoacoustic imaging preparations
• CPC Class Codes: A61K 49/223 Microbubbles, hollow microspheres, free gas bubbles, gas microspheres
• CPC Class Codes: A61K 49/227 Liposomes, lipoprotein vesicles, e.g. LDL or HDL lipoproteins, micelles, e.g. phospholipidic or polymeric
• CPC Class Codes: A61K 9/127 Liposomes
• CPC Class Codes: A61K 9/1271 Non-conventional liposomes, e.g. PEGylated liposomes, liposomes coated with polymers liposome as conjugate A61K47/6911
• CPC Class Codes: A61K 9/1277 Processes for preparing; Proliposomes
• CPC Class Codes: A61K 9/1278 Post-loading, e.g. by ion or pH gradient
• CPC Class Codes: A61M 5/3145 Filters incorporated in syringes
• CPC Class Codes: G01R 33/5601 involving use of a contrast agent for contrast manipulation, e.g. a paramagnetic, super-paramagnetic, ferromagnetic or hyperpolarised contrast agent

Abstract

Lyophilized lipid compositions, as well as methods for their preparation, are embodied by the present invention. Gas-filled microspheres prepared using the lyophilized lipid composition are particularly useful, for example, in ultrasonic imaging applications and in therapeutic drug delivery systems.

Claims

1. A method of preparing a gas-filled microsphere comprising:

a. obtaining a lyophilized lipid composition comprising the lipids dipalmitoylphosphatidylcholine, dipalmitoylphosphatidylethanolamine-polyethylene glycol, and dipalmitoylphosphatidic acid, in a ratio of about 70 to about 90 mole percent, about 5 to about 15 mole percent, and about 5 to about 15 mole percent, respectively, wherein the combined concentration of lipids is about 20 mg/ml to about 50 mg/ml of aqueous solution prior to lyophilizing;

b. dispersing said lyophilized composition in an aqueous-based pharmaceutically acceptable carrier to a concentration of about 0.1 mg/ml to about 5 mg/ml to form an aqueous microsphere-forming solution;

c. introducing a fluorine-containing gas into said aqueous microsphere-forming solution; and

d. shaking said aqueous microsphere-forming solution to form a microsphere filled with fluorine-containing gas.

2. The method of claim 1 wherein the shaking step comprises vortexing.

3. The method of claim 1 further comprising filtering said aqueous microsphere-forming solution.

4. The method of claim 1 further comprising extruding said aqueous microsphere-forming solution through at least one filter of a selected pore size.

5. The method of claim 4 wherein the pore size is about 10 μ

m or smaller.

6. The method as in claim 4 wherein the pore size is about 0.22 μ

m.

7. The method of claim 1 further comprising heating said aqueous microsphere-forming solution.

8. The method of claim 4 further comprising dispersing said aqueous microsphere-forming solution into at least one vessel.

9. The method of claim 1 wherein step c. comprises placing a vessel containing said aqueous microsphere-forming solution in a chamber and introducing a fluorine-containing gas into said chamber, and step d. comprises shaking said vessel to form a microsphere filled with fluorine-containing gas.

10. The method of claim 9 further comprising pressurizing said vessel.

11. The method of claim 1 wherein step c. comprising placing a vessel containing said aqueous microsphere-forming solution in a pressurized chamber, evacuating the chamber of gas, and filling the chamber with a fluorine- containing gas such that the head space of the vessel is filled with a fluorine-containing gas and step d. comprises shaking said vessel to form a microsphere filled with a fluorine-containing gas.

12. The method of claim 1 wherein said aqueous solution is selected from the group consisting of water, physiological saline, and normal saline.

13. The method of claim 1 wherein said pharmaceutically acceptable carrier is selected from the group consisting of a mixture of water, glycerol, and propylene glycol and a mixture of saline, glycerol, and propylene glycol, in a ratio of 8:

1;

1, v;

v;

v, respectively.

14. The method of claim 1 wherein said fluorine-containing gas is selected from the group consisting of sulfur hexafluoride and a perfluorocarbon.

15. The method of claim 14 wherein said perfluorocarbon is selected from the group consisting of perfluoropropane, perfluoropentane, perfluorohexane, and perfluorobutane.

16. A method of claim 1 wherein said lipids comprise a monolayer.

17. A method of claim 16 wherein said gas is selected from the group consisting of sulfur hexafluoride and a perfluorocarbon.

18. A method of claim 17 wherein said perfluorocarbon is selected from the group consisting of perfluorobutane, perfluoropropane, perfluoropentane, and perfluorohexane.