Highly asymmetric, hydrophilic, microfiltration membranes having large pore diameters

• US 7,125,493 B2
• Filed: 08/16/2004
• Issued: 10/24/2006
• Est. Priority Date: 12/12/1996
• Status: Expired due to Term

• Current Assignee: Pall Corporation (Danaher Corporation)
• Original Assignee: Pall Corporation (Danaher Corporation)
• Inventors: Morris, Richard A., Wang, I-Fan, Zepf, Robert F.
• Primary Examiner(s): FORTUNA, ANA M
• Application Number:
  US10/918,871
• Publication Number:
  US 20050011834A1
• Time in Patent Office: 799 Days
• Field of Search: 210/645, 210/500.22, 210/321.75, 210/500.41, 210/500.42, 210/321.84, 210/489, 210/500.24, 264/49, 422/101, 422/56, 422/60, 436177-178, 436/170
• US Class Current: 210/645
• CPC Class Codes: B01D 2323/02 Hydrophilization
• CPC Class Codes: B01D 2323/08 Specific temperatures applied
• CPC Class Codes: B01D 2323/081 Heating
• CPC Class Codes: B01D 2323/12 Specific ratios of components used
• CPC Class Codes: B01D 2325/02 Details relating to pores or porosity of the membranes
• CPC Class Codes: B01D 2325/022 Asymmetric membranes
• CPC Class Codes: B01D 2325/0283 Pore size
• CPC Class Codes: B01D 2325/02834 more than 0.1 and up to 1 µm
• CPC Class Codes: B01D 2325/04 Characteristic thickness
• CPC Class Codes: B01D 2325/36 Hydrophilic membranes
• CPC Class Codes: B01D 39/16 of organic material, e.g. synthetic fibres
• CPC Class Codes: B01D 67/0011 Casting solutions therefor
• CPC Class Codes: B01D 67/0013 Casting processes
• CPC Class Codes: B01D 67/00135 Air gap characteristics
• CPC Class Codes: B01D 67/0016 Coagulation
• CPC Class Codes: B01D 69/02 characterised by their properties
• CPC Class Codes: B01D 69/12 Composite membranes; Ultra-thin membranes
• CPC Class Codes: B01D 69/1216 Three or more layers
• CPC Class Codes: B01D 71/68 Polysulfones; Polyethersulfones
• CPC Class Codes: Y10T 428/24992 Density or compression of components
• CPC Class Codes: Y10T 428/249961 : With gradual property change within a component
• CPC Class Codes: Y10T 428/249979 : Specified thickness of void-containing component [absolute or relative] or numerical cell dimension
• CPC Class Codes: Y10T 428/24998 : Composite has more than two layers
• CPC Class Codes: Y10T 428/249989 : Integrally formed skin
• CPC Class Codes: Y10T 428/2975 : Tubular or cellular
• CPC Class Codes: Y10T 436/25375 : Liberation or purification of sample or separation of material from a sample [e.g., filtering, centrifuging, etc.]
• CPC Class Codes: Y10T 436/255 : including use of a solid sorbent, semipermeable membrane, or liquid extraction

Abstract

The present invention relates to the field of synthetic polymeric microfiltration membrane materials that are fabricated to separate liquids from solids contained therein. One aspect of the invention relates to a highly asymmetric, hydrophilic microfiltration membrane with high surface porosity. The membrane is rendered hydrophilic through co-casting the sulfone polymer with a hydrophilic polymer, such as polyvinylpyrrolidone. The membranes of the invention are highly useful in testing devices for the quick detection of properties or components contained in liquid samples, such as diagnostic applications, as well as for other filtration applications that demand relatively large pore sizes, thick membranes, high asymmetry, and/or high lateral wicking speeds.

Claims

1. A blood separation device, the device comprising an asymmetric integral sulfone polymer membrane, the asymmetric membrane rendered hydrophilic through co-casting a sulfone polymer with a hydrophilic polymer, the asymmetric membrane comprising a first microporous skin surface, a porous support, and a second coarse pored surface, the microporous skin surface possessing skin pores, the skin pores having an average diameter of from about 0.1 micron to about 10 microns, the porous support comprising an asymmetric region of gradually increasing pore sizes, wherein pores on the second coarse pored surface have an average diameter of about 5 times to about 1000 times the diameter of the skin pores, wherein the device is capable of separating a first component of blood from a second component of blood based on a size difference between the first component and the second component.

2. The blood cell separation device of claim 1, wherein the first component comprises plasma and the second component comprises blood cells.

3. The blood cell separation device of claim 1, wherein the first component comprises blood platelets and the second component comprises large blood cells.

4. The blood cell separation device of claim 3, wherein the large blood cells are selected from the group consisting of leukocytes, lymphocytes, platelets, neutrophils, B-cells, T-cells, monocytes, macrophages, and mixtures thereof.

5. The blood cell separation device of claim 1, wherein a surface of the asymmetric membrane is charge-modified.

6. The blood cell separation device of claim 1, wherein the blood separation device comprises a vertical wicking device.

7. The blood cell separation device of claim 6, further comprising a collector membrane, wherein the microporous skin surface of the asymmetric membrane is in intimate contact with the collector membrane.

8. The blood cell separation device of claim 7, wherein the collector membrane comprises an analyte detection system.

9. The blood cell separation device of claim 1, wherein the blood separation device comprises a lateral wicking device.

10. The blood cell separation device of claim 9, wherein the blood separation device further comprises a contact membrane, wherein the contact membrane and the asymmetric membrane are in contact at an interface.

11. The blood cell separation device of claim 10, wherein the contact membrane comprises a detection indicator capable of detecting a presence or absence of an agent being detected.

12. The blood cell separation device of claim 11, wherein the detection indicator comprises a chemical reactant.

13. The blood cell separation device of claim 11, wherein the detection indicator is selected from the group consisting of an enzyme, an antigen-linked reagent, and an antibody-linked reagent.

14. The blood cell separation device of claim 10, wherein the contact membrane comprises a nitrocellulose membrane.

15. The blood cell separation device of claim 9, wherein the asymmetric membrane possesses a lateral wicking speed of water of at least about 5 mm/second.

16. The blood cell separation device of claim 1, wherein the asymmetric membrane has a bulk void porosity of about 80 percent or more.

17. The blood cell separation device of claim 1, wherein the asymmetric membrane comprises a mean flow pore size of from about 0.1 μ

m to about 10 μ

m.

18. The blood cell separation device of claim 1, wherein the asymmetric membrane possesses a density of skin pores of at least about 15 pores per 1000 μ

m².

19. The blood cell separation device of claim 1, wherein the asymmetric membrane has a thickness of from 100 microns to 340 microns.

20. The blood cell separation device of claim 1, wherein the sulfone polymer is selected from the group consisting of polysulfone, polyethersulfone, and polyarylsulfone.

21. The blood cell separation device of claim 1, wherein the hydrophilic polymer comprises polyvinylpyrrolidone.

22. A method for separating large blood cells from red blood cells based on a size difference between the large blood cells and the red blood cells, the method comprising:

providing a blood separation device, the device comprising an asymmetric integral sulfone polymer membrane, rendered hydrophilic through co-casting a sulfone polymer with a hydrophilic polymer, the asymmetric membrane comprising a first microporous skin surface, a porous support, and a second coarse pored surface, the microporous skin surface possessing skin pores, the skin pores having an average diameter of from about 0.1 micron to about 10 microns, the porous support comprising an asymmetric region of gradually increasing pore sizes, wherein pores on the second coarse pored surface have an average diameter of about 5 times to about 1000 times the diameter of the skin pores, and the device further comprising a collector membrane, wherein the collector membrane contacts the first microporous skin surface of the asymmetric membrane; and

contacting a blood sample with the second coarse pored surface, whereby a first component of the blood sample passes through the asymmetric membrane, and whereby a second component of the blood sample is filtered out in pores of the asymmetric membrane, the first component of the blood sample having a smaller size than the second component.

23. The method of claim 22, wherein the blood separation device comprises a lateral wicking device, wherein the device further comprises a contact membrane in contact with the microporous skin surface of the asymmetric membrane, and wherein the contact membrane comprises a detection indicator, the method further comprising the step of:

contacting the first component with the contact membrane, such that the detection indicator detects a presence or an absence of an agent in the first component.

24. The method of claim 22, wherein the blood separation device comprises a vertical wicking device, wherein the device further comprises a collector membrane in intimate contact with the microporous skin surface of the asymmetric membrane, and wherein the collector membrane comprises an analyte detection system, the method further comprising the step of:

collecting the first component in the collector membrane, such that the analyte detection system detects a presence or an absence of an analyte in the first component.