METHOD AND APPARATUS FOR THE FILTRATION OF BIOLOGICAL SAMPLES

Abstract

A separation module and method are disclosed for processing a liquid sample and providing high conversion by operating a single-pass tangential-flow process without a recirculation loop. In one embodiment, the separation module includes three reservoirs and has at least one long, thin channel with a large ratio of channel membrane area to: channel void volume; volume of a sample feed reservoir; and volume of the feed sample. In another embodiment, the separation module includes two reservoirs and a hydrophobic vent. The single-pass process provides high conversion while operating with relatively low pressure sources.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other aspects, embodiments, objects, features and advantages of the present teachings can be more fully understood from the following description in conjunction with the accompanying drawings. In the drawings, like reference characters generally refer to like features and structural elements throughout the various figures. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the present teachings.

FIGS. 1A and 1B are schematic diagrams of 3-volume devices according to the invention;

FIG. 2 is a schematic diagram of a 3-volume device similar to the devices of FIG. 1A suitable for operation in a centrifuge;

FIG. 3 is a longitudinal cross section view of flow a channel formed with hollow fiber membrane according to the present invention;

FIG. 4 is a longitudinal cross section view of a flow channel formed with flat-sheet membranes according to the present invention;

FIGS. 5A and 5B are schematic diagrams of instrumented systems incorporating the devices of FIGS. 1A and 1B;

FIG. 6A is a cross-sectional view of a 3-volume device including a separation element comprising a hollow fiber membrane and suitable for use in multi-well plates according to the present invention;

FIG. 6B is a cross-sectional view of the device of FIG. 6A, through line 6B of FIG. 6A, showing further details of the separation element;

FIG. 7A is a cross-sectional view of a 3-volume device including a separation element comprising spiral-wound membrane and suitable for use in multi-well plates according to the present invention;

FIG. 7B is a cross-sectional view of the device of FIG. 7A, through line 7B of FIG. 7A, showing further details of the separation element;

FIG. 8 is a flow diagram illustrating the steps used to process a sample and recover the retentate or permeate fractions using the devices of FIGS. 1A, 1B, and 2;

FIGS. 9A and 9B are graphs of flux and conversion vs. time for Example 1A;

FIGS. 10A and 10B are graphs of flux and conversion vs. time for Example 1B;

FIGS. 11A and 11B are schematic diagrams of 2-volume devices including hydrophobic vents according to the invention;

FIG. 12 is a schematic diagram of a 2-volume device similar to the devices of FIG. 11A suitable for operation in a centrifuge;

FIG. 13 is a schematic diagram of 2-volume device including a hydrophobic vent in which the separation element is integrated into the permeate reservoir according to the invention;

FIG. 14 is a schematic diagram of a 2-volume device in which the flow channel carries the permeate to the permeate reservoir and the separation element is integrated into the feed reservoir according to the invention;

FIG. 15 is a flow diagram illustrating the steps used to process a sample and recover the retentate or permeate fractions using the devices of FIGS. 11A, 11B, and 12; and

FIG. 16 is a schematic diagram a 2-volume hollow fiber module suited for small volume samples where pressure differentials are induced by capillary forces according to the invention.

Claims

1. A separation module for the filtration of a liquid sample comprising: a separation element comprising at least one flow channel having an inlet, an outlet and a surface comprising an ultrafiltration membrane;a feed reservoir fluidly coupled to the channel inlet;a retentate reservoir fluidly coupled to the channel outlet;a permeate reservoir fluidly coupled to the separation element; andwherein the ratio of the membrane area of the separation element to the volume of the feed reservoir is greater than about 2 cm−1.

2. The module of claim 1 further comprising: a first pressure source coupled to one of: the feed reservoir;the retentate reservoir;the permeate reservoir; anda second pressure source coupled to another one of: the feed reservoir;the retentate reservoir;the permeate reservoir.

3. The module of claim 2 wherein each of the first pressure source and the second pressure source is one of: a vacuum source;a water siphon providing a vacuum;a compressed gas source;a pump; anda centrifugal pressure source.

4. The module of claim 2 further comprising a valve fluidly coupled to the feed reservoir and disposed opposite the channel inlet.

5. The module of claim 1 wherein the at least one flow channel has a length adapted to provide a relatively large and controllable value of TCP and is characterized by dimensionless parameter, α greater than about 10,000.

6. The module of claim 1 further comprising a first pressure source port coupled to the permeate reservoir and a second pressure source port coupled to the retentate reservoir.

7. The module of claim 1 wherein the specific membrane area of the at least one channel is greater than about 80 cm−1.

8. The module of claim 1 further comprising a central core forming the retentate reservoir, channel further comprises at least one hollow fiber wound annularly around the central core and having a dimensionless length greater than about 2,000.

9. The module of claim 1 wherein the separation element comprises one of: a hollow fiber membrane;a flat-sheet membrane;a membrane monolith; anda spiral-wound element.

10. The module of claim 1 further comprising a central core forming the retentate reservoir, channel further comprises at least one spiral wound element disposed annularly around the central core and having a dimensionless length greater than about 500.

11. The module of claim 1 wherein the feed reservoir, the retentate reservoir and the permeate reservoir are juxtaposed along a centrifugal acceleration vector, the retentate reservoir interposed between the feed reservoir and the permeate reservoir.

12. A separation module for the filtration of a liquid sample comprising: a separation element comprising at least one flow channel having an inlet, a surface comprising a filtration membrane; and a hydrophobic vent affixed to the channel distally from the inlet;a feed reservoir fluidly coupled to the channel inlet; anda permeate reservoir fluidly coupled to the separation element.

13. The module of claim 12 wherein the specific membrane area of the at least one flow channel is greater than about 80 cm−1.

14. The module of claim 12 wherein the hydrophobic vent comprises a hydrophobic membrane with a pore size less that about 10 micrometers.

15. The module of claim 12 wherein the at least one flow channel is disposed within the permeate reservoir.

16. The module of claim 12 wherein the separation element comprises one of: a hollow fiber membrane;a flat-sheet membrane; anda membrane monolith.

17. A separation module for the filtration of a liquid sample comprising: a separation element comprising at least one flow channel having an outlet, a surface comprising a filtration membrane;a feed reservoir;a permeate reservoir fluidly coupled to the outlet; andwherein the at least one flow channel is disposed within the feed reservoir.

18. The module of claim 17 wherein the membrane is disposed on the outside surface of the flow channel.

19. The module of claim 17 wherein and the specific membrane area of the module is greater than about 2 cm−1.

20. The module of claim 17 wherein and the specific membrane area of the at least one channel is greater than about 80 cm−1.

21. A separation module for the filtration of a liquid sample comprising: a hollow fiber having a thick wall forming a permeate reservoir and a thin lumen adapted to provide capillary motion of the liquid within the lumen.

22. The module of claim 21 wherein the at least one flow channel has a specific membrane area greater than about 200 cm−1 and a dimensionless length greater than about 200.

23. The module of claim 22 wherein the diameter of the lumen is less than about 100 μm and the wall thickness is greater than about 125 μm.

24. The module of claim 23 wherein the length of the lumen is greater than about 6 cm.

25. The module of claim 21 further comprising analytical device disposed within the lumen at an end opposite the inlet.

26. The module of claim 25 wherein the analytical device comprises an electrophoresis column.

27. A method for filtering a liquid sample comprising: supplying a predetermined volume of the liquid sample into a feed reservoir of a separation module comprising: a separation element having at least one flow channel having an inlet, an outlet and surface comprising a filtration membrane;the feed reservoir fluidly coupled to the channel inlet;a retentate reservoir fluidly coupled to the channel outlet;a permeate reservoir fluidly coupled to the separation element;wherein the ratio of the membrane area of the separation element to the volume of the feed reservoir is greater than about 2 cm−1;inducing the tangential flow of the liquid sample in the at least one flow channel by applying a first pressure differential between the feed reservoir and retentate reservoir; andinducing the permeation of a portion of the liquid sample through the filtration membrane into the permeate reservoir by applying a second pressure differential between one of:the retentate reservoir and permeate reservoir;the feed reservoir and permeate reservoir.

28. The method of claim 27 further comprising independently controlling TCP and TMP by controlling the first and second pressure differentials independently of each other.

29. The method of claim 27 wherein the sample filtering time is a function of a ratio of the membrane area of the separation element to the predetermined volume of the liquid sample.

30. The method of claim 29 wherein the ratio is greater than about 2 cm−1.

31. The method of claim 29 wherein the specific membrane area of the at least one flow channel is greater than about 80 cm−1.

32. The method of claim 27 wherein the first and second pressure differential are provided by at least one of: a compressed gas source;a vacuum source;a capillary force;an osmotic force;a pump; anda centrifugal force.

33. The method of claim 27 further comprising recovering a non-permeating fraction of the liquid sample, the step comprising: substantially dissipating the first and second pressure differentials before fully consuming the liquid sample in the feed reservoir to stop permeation and tangential flow in the separation module; anddisplacing the residual liquid sample within the channel by applying a third pressure differential between the feed and retentate reservoirs to induce flow of the liquid sample into the retentate reservoir.

34. The method of claim 27 further comprising recovering a non-permeating fraction of the liquid sample, the step comprising: substantially consuming the liquid sample in the feed reservoir; andsubstantially dissipating the first and second pressure differentials to stop permeation and tangential flow in the separation module.

35. The method of claim 34 further comprising displacing the residual liquid sample within the channel by applying a third pressure differential between the feed and retentate reservoirs to induce flow of the liquid sample into the feed reservoir.

36. The method of claim 34 further comprising: inducing reverse permeation by applying a third pressure differential between the permeate and retentate reservoirs to induce flow of the liquid sample into the retentate reservoir; anddisplacing the residual liquid sample within the channel; andwithdrawing the retentate from the retentate reservoir.

37. The method of claim 34 further comprising: introducing a buffer to the feed reservoir;displacing the residual liquid sample within the channel by applying a third pressure differential between the feed and retentate reservoirs to induce flow of the liquid sample into the retentate reservoir.

38. The method of claim 34 further comprising: inducing reverse permeation by applying a third pressure differential between the permeate and feed reservoirs;displacing the residual liquid sample within the channel; andwithdrawing the retentate from the feed reservoir.

39. A method for filtering a liquid sample comprising: supplying a predetermined volume of liquid sample into a feed reservoir of a separation module comprising: a separation element having at least one flow channel having an inlet and a surface comprising a filtration membrane;the feed reservoir fluidly coupled to the channel inlet;a permeate reservoir disposed adjacent the channel surface;a hydrophobic vent affixed to the channel distally from the inlet;inducing tangential flow within the flow channel and the permeation of a portion of the liquid sample through the filtration membrane into the permeate reservoir by applying a pressure differential between the feed reservoir and permeate reservoir; andinducing the flow of the liquid sample in the at least one flow channel by venting the flow channel.

40. The method of claim 39 wherein the specific membrane area of the at least one channel is greater than about 80 cm−1.

41. The method of claim 39 wherein the pressure differential between the feed reservoir and the permeate reservoir is less than about 50 psi.

42. The method of claim 39 further comprising accumulating the non-permeating liquid fraction in the at least one flow channel.

43. The method of claim 39 wherein the pressure differential driving force is provided by at least one of: a compressed gas source;a vacuum source;a capillary force;a pump; anda centrifugal pressure source.

44. The method of claim 39 wherein the sample filtering time is a function of the predetermined volume of the liquid sample and the ratio of the membrane area of the separation element to the volume of the feed reservoir.

45. The method of claim 44 wherein the ratio is greater than about 2 cm−1.

46. The method of claim 39 further comprising: recovering a non-permeating fraction of the liquid sample, the step comprising:substantially consuming the liquid sample in the feed reservoir; andsubstantially dissipating the pressure differential to stop permeation and tangential flow in the separation module.

47. The method of claim 46 further comprising: inducing a pressure differential between the vent and the feed reservoir to induce the infiltration of gas into the flow channel and displacing the residual liquid within the channel volume towards the feed reservoir; andwithdrawing the non-permeating fraction of the liquid sample from the feed reservoir.

48. The method of claim 46 further comprising withdrawing the permeate.

49. The method of claim 46 further comprising: inducing reverse permeation to displace the non-permeating fraction towards the feed reservoir; andwithdrawing the non-permeating fraction of the liquid sample from the feed reservoir.

50. The method of claim 49 wherein inducing reverse permeation comprises the steps of inducing a second pressure differential between the permeate and the feed reservoirs and displacing the residual liquid within the channel volume in flow towards the feed reservoir.

51. A method for filtering a liquid sample in a sample reservoir comprising: dipping a hollow fiber separation module into the sample reservoir, the module comprising a separation element comprising: a lumen comprising an ultrafiltration membrane and having an inlet, a flow channel coupled to the inlet, and a wall at least partially surrounding the channel,drawing a predetermined volume of liquid sample into the lumen by capillary action by leaving the inlet in the sample reservoir for a predetermined time;inducing the tangential flow of the liquid sample in the lumen by capillary action; andinducing, by capillary action, permeation of a portion of the liquid sample through the membrane into a permeate reservoir formed by an inner and outer surface of the lumen wall.

52. The method of claim 51 further comprising withdrawing the retentate from the lumen by one of: a micro-bore syringe;vacuum force; andcentrifugal force.

53. The method of claim 51 further comprising withdrawing a portion of the retentate from the lumen by electro-osmosis.

54. The method of claim 51 wherein the predetermined time is a function of the predetermined volume of liquid sample and a ratio of the membrane area of the lumen to the volume of the feed sample drawn into the lumen.

55. The method of claim 54 wherein the ratio is greater than about 2 cm−1.