Filtration methods and devices
A method of filtering a liquid sample that includes passing a sample comprising at least one biological organism through a filter membrane at a passive water volume flux of at least 10 L/m 2 ·h·psi, wherein the filter membrane comprises a Bubble Point pore size of no more than 1.0 μm, thereby retaining at least one biological organism on the surface of the membrane; and detecting the at least one biological organism retained on the surface of the filter membrane.
1. A method comprising:
providing a device that comprises:
a pocket comprising a pocket surface that defines a pocket volume;
an absorbent member disposed on at least a portion of the pocket surface; and
a filter membrane disposed on at least a portion of the absorbent member in fluid communication with the pocket volume, wherein the filter membrane is in functional communication with the absorbent member, wherein the functional communication is capable of generating a water flux gradient sufficient to draw liquid across the filter membrane and into the absorbent member, wherein the absorbent member is enveloped by the filter membrane;
passing a sample having a sample volume and comprising at least one biological organism through the filter membrane at a passive water volume flux of at least 10 L/m 2 ·h·psi, wherein the filter membrane comprises a Bubble Point pore size of no more than 1.0 μm, thereby retaining at least one biological organism on a surface of the filter membrane; and
detecting the at least one biological organism retained on the surface of the filter membrane;
wherein passing the sample through the filter membrane comprises:
adding the sample to the pocket volume; and
permitting the absorbent member to absorb at least 50% of the sample volume.
2. The method of claim 1 wherein the passive water volume flux is at least 32 L/m 2 ·h·psi.
3. The method of claim 1 wherein the passive water volume flux is at least 88 L/m 2 ·h·psi.
4. The method of claim 1 wherein the Bubble Point pore size is no more than 0.8 μm.
5. The method of claim 1 wherein the Bubble Point pore size is no more than 0.2 μm.
6. The method of claim 1 wherein at least 30% of the biological organisms in the sample are retained on the surface of the filter membrane.
7. The method of claim 1 wherein at least 70% of the biological organisms in the sample are retained on the surface of the filter membrane.
8. The method of claim 1 wherein at least 90% of the biological organisms in the sample are retained on the surface of the filter membrane.
9. The method of claim 1 wherein at least 99% of the biological organisms in the sample are retained on the surface of the filter membrane.
10. The method of claim 1 wherein at least 99.5% of the biological organisms in the sample are retained on the surface of the filter membrane.
11. The method of claim 1 wherein the at least one biological organism is detected in situ on the surface of the filter membrane.
12. The method of claim 1 wherein detecting the at least one biological organism retained on the surface of the filter membrane comprises eluting the retained biological organism from the surface of the membrane prior to performing a detection assay.
13. The method of claim 12 wherein at least 50% of the retained biological organisms are eluted from the surface of the filter membrane.
14. The method of claim 13 wherein at least 90% of the retained biological organisms are eluted from the surface of the filter membrane.
15. The method of claim 1 wherein detecting the at least one biological organism comprises at least one of the following:
contacting the biological organism with an antibody composition that specifically binds to the biological organism;
detecting an enzyme activity of the biological organism;
detecting a biological analyte of the biological organism;
detecting a biological analyte produced by the biological organism, followed by detecting a portion of a nucleic acid from the biological organism;
amplifying at least a portion of a nucleic acid molecule from the biological organism; and
detecting the nucleotide sequence of the biological organism.
16. The method of claim 1 wherein the filter membrane comprises a polyolefin porous membrane, an ethylene-chlorotrifluoroethylene copolymer porous membrane, a polyacrylonitrile porous membrane, a polycarbonate porous membrane, a polyester porous membrane, a cellulose ester porous membrane, a polyamide porous membrane, a polyethersulfone porous membrane, a polysulfone porous membrane, a polyvinylidene fluoride (PVDF) porous membrane, a polyacrylonitrile nanofiber membrane, a PVDF nanofiber membrane, a cellulose ester nanofiber membrane, a polyvinyl acetate or alcohol nanofiber membrane, or a polyvinyl butyral nanofiber membrane.
17. The method of claim 1 wherein the filter membrane comprises a thermally-induced phase separation (TIPS) membrane or a nanofiber membrane.
18. The method of claim 1 wherein the at least one biological organism is detected no more than 24 hours after the sample is passed through the filter membrane.
19. The method of claim 18 wherein the at least one biological organism is detected no more than 12 hours after the sample is passed through the filter membrane.
20. The method of claim 19 wherein the at least one biological organism is detected no more than three hours after the sample is passed through the filter membrane.
21. The method of claim 1 wherein the sample comprises food.
22. The method of claim 1 wherein the sample comprises an environmental sample.
23. The method of claim 1 wherein the sample comprises a water sample.
24. The method of claim 1 further comprising performing an assay to quantify the detected biological organisms recovered from the surface of the filter membrane.