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|Title:||Method for size separation of particles|
|Abstract:||Tangential flow filtration is used in the size separation of particles, such as liposomes and lipid particles. These particles may be passed through a tangential flow filtration device of any pore size desired. Tangential flow filter systems of various pore sizes may be used sequentially to obtain particles such as lipid particles or liposomes having a defined size range.|
|Inventor(s):||Lenk; Robert P. (Lambertville, NJ), Durning; Anthony G. (Yardley, PA), Klimchak; Robert J. (Flemington, NJ), Portnoff; Joel (Richboro, PA), Tomsho; Michelle L. (Levittown, PA)|
|Assignee:||The Liposome Company, Inc. (Princeton, NJ)|
|Filing Date:||Jan 03, 1995|
|Claims:||1. A method of producing nonliposomal lipid particles of a homogeneous, defined size distribution from a mixture of lipid particles of heterogeneous size comprising the steps of: |
(a) subjecting the mixture to tangential flow filtration with a first filter of a first pore size;
(b) subjecting the filtrate from step (a) to tangential flow filtration with a second filter of a second, smaller pore size; and
(c) collecting the retentate from step (b),
wherein the first pore size defines the upper limit of the size distribution of the liposomes or lipid particles, the first pore size is between about 10 and about 0.2 microns, the second pore size defines the lower limit of size distribution of the particles and the second pore size is between about 2000 molecular weight and about 2 microns.
2. The method of claim 1 wherein the lipid particles additionally comprise a bioactive agent.
3. The method of claim 2 wherein the bioactive agent comprises a polyene antifungal agent.
4. The method of claim 3 wherein the polyene antifungal agent comprises amphotericin B and wherein the lipid particles comprise a lipid which comprises dimyristoyl phosphatidylcholine and dimyristoyl phosphatidylglycerol.
5. The method of claim 1 wherein the first pore size is about 5 um.
6. The method of claim 1 wherein the second pore size is about 1.0 um.
7. The method of claim 1 further comprising the step of milling the lipid particles to reduce their size prior to their application to a tangential flow filter.
8. A population of lipid particles with a homogeneous defined size distribution prepared by tangential flow filtration in accordance with the method of claim 1.
9. The population of claim 8 wherein the lipid particles comprise a lipid and a bioactive agent.
10. A method of producing nonlipoosmal lipid particles of a size having sizes below a defined size cutoff comprising the steps of:
(a) homogenizing the particles:
(b) subjecting the particles to tangential flow filtration with a first filter of a pore size which excludes particles above the defined cutoff;
(c) collecting the filtrate from step (b) and,
(d) subjecting the collected filtrate from step (c) to tangential flow filtration with a second filter of smaller pore size.
11. A method for preparing a liposome or lipid particle comprising the step of contacting a solution containing lipid to a first side of a filter in tangential flow filtration apparatus while infusing or injecting an aqueous solution to a second side of the filter in the tangential flow filtration apparatus.
12. The method of claim 11 wherein the tangential flow filtration system employed is a dynamic rotary filtration or a hollow fiber filtration.