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|Title:||Method of preparing gas-filled microspheres using a lyophilized lipids|
|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.|
|Inventor(s):||Unger; Evan C. (Tucson, AZ), Fritz; Thomas A. (Tucson, AZ), Matsunaga; Terry (Tucson, AZ), Ramaswami; VaradaRajan (Tucson, AZ), Yellowhair; David (Tucson, AZ), Wu; Guanli (Tucson, AZ)|
|Assignee:||ImaRx Pharmaceutical Corp. (Tucson, AZ)|
|Filing Date:||Apr 30, 1996|
|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 .mu.m or smaller.
6. The method as in claim 4 wherein the pore size is about 0.22 .mu.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.
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