Adhered membranes retaining porosity and biological activity
An assay pad for measuring the concentration of HDL-associated cholesterol in a sample, a method for using the pad, and a diagnostic assay device for carrying out the method are described. The assay pad includes a polymer adhesive or heat laminate bond. The assay design prevents interference by reagents used for such removal with the HDL quantification reaction or with other assays carried out on the same sample. If desired, removal of non-HDL lipoproteins and assay of HDL cholesterol can be carried out without interruption of the assay.
1. An assay device for measuring serum cholesterol associated with high-density lipoproteins (HDL) in a blood fluid sample containing lipoproteins other than HDLs of the type including a sample distribution array effective to distribute a blood fluid sample from a sample application region to one or more sample collection regions, the device comprising:
a HDL test pad in which HDL concentration can be assayed being spaced apart from said array, said HDL test pad being affixed to a mounting means; and
a reagent pad containing a binding reagent effective to selectively bind and remove non-HDLs from the fluid sample;
wherein said HDL test pad and said reagent pad are joined by a bond selected from the group consisting of a heat formed bond and heat activated adhesive bond;
wherein said mounting means are effective (i) to maintain the device in a sample-distribution position, wherein said joined HDL test pad and reagent pad are spaced apart from said array, and (ii) to transfer said device to a test position, whereby the joined HDL test pad and reagent pad are in contact with said array.
2. The device of claim 1 , wherein at least one of said HDL test pad or said reagent pad is composed of a polysulfone layer.
3. The device of claim 1 , further comprising a sieving pad in fluid communication with said sample application region and said one or more sample collection regions effective to remove cellular components from the blood fluid sample prior to the sample contacting said sample distribution array.
4. The device of claim 3 , further comprising a cassette body for containing said sieving pad, said cassette body comprising a well for containing said blood fluid sample and in fluid communication with said sieving pad.
5. The device of claim 4 , further comprising a reaction bar comprising mounting means effective to attach said reaction bar to said cassette body.
6. The device of claim 1 , wherein said reagent comprises a binding polyanionic reagent.
7. The device of claim 6 , wherein said binding polyanionic reagent includes a sulfonated polysaccharide.
8. The device of claim 1 , wherein said HDL test pad contains reagents which produce a detectable change in the presence of HDL cholesterol.
9. The device of claim 8 , wherein said change can be detected optically.
10. The device of claim 1 , wherein said HDL test pad comprises a biosensor.
11. The device of claim 10 , wherein said biosensor is effective to electrochemically measure production of oxygen or hydrogen peroxide.
12. The device of claim 1 , wherein said bond extends along the periphery of at least one of the HDL test pad and the reagent pad.
13. The device of claim 1 , wherein said bond extends along the entire surface of at least one of the HOL test pad and the reagent pad.
14. The assay device of claim 1 , wherein said heat activated adhesive bond is an acrylic acid copolymer adhesive bond.
15. The device of claim 14 , wherein said acrylic acid copolymer is ethylene acrylic acid copolymer.
16. A method of preparing a device suitable for measuring serum cholesterol comprising:
providing a reagent pad and an HDL test pad, wherein at least the reagent pad is formed of an asymmetric polysulfone membrane having a small pore side and an open pore side;
heating to adhere said HDL test pad and said reagent pad; and
applying (i) HDL test reagents to said HDL test pad, and (ii) a reagent effective to selectively bind and remove non-HDLs from a fluid sample to said reagent pad to form said device.
17. The method of claim 16 , wherein said heating is at a temperature above 165° C.
18. The method of claim 16 , wherein each of said HDL test pad and said reagent pad are formed of an asymmetric polysulfone membrane having a small pore side and an open pore side, said method further comprising:
before said heating, orienting the reagent pad with the HDL test pad such that the small pore side of the reagent pad contacts the open pore side of the HDL test pad.
19. The method of claim 16 , wherein the periphery of at least one of the HDL test pad and the reagent pad is heated.
20. The method of claim 16 , wherein the entire surface of at least one of the HDL test pad and the reagent pad is heated.
21. A method of preparing a device suitable for measuring serum cholesterol comprising:
coating a reagent pad with heat activated adhesive;
applying (i) HDL test reagents to an HDL test pad, and (ii) a reagent effective to selectively bind and remove non-HDLs from a fluid sample to said reagent pad;
heating to adhere said HDL test pad and said reagent pad to form said device.
22. The method of claim 21 , further comprising the step of drying said reagent pad after said coating step.
23. The method of claim 21 , wherein each of said HDL test pad and reagent pad have a small pore side and an open pore side; further comprising the step of orienting the HDL test pad and the reagent pad such that the small pore side of the reagent pad faces the open pore side of the HDL test pad.
24. The method of claim 21 , wherein said heating step comprises applying a temperature of between 75° and 90° C.
25. The method of claim 21 , wherein the periphery of the reagent pad is coated with the heat activated adhesive.
26. The method of claim 21 , wherein the entire surface of the reagent pad is coated with the heat activated adhesive.
27. The method of claim 21 , wherein said heat activated adhesive is an acrylic acid copolymer adhesive.
28. The method of claim 27 , wherein said acrylic acid copolymer is ethylene acrylic acid copolymer.
29. The method of claim 28 , wherein the ethylene acrylic acid copolymer is about 4.0% to about 10.0% emulsion.
30. A method of measuring serum cholesterol associated with high-density lipoproteins (HDL) in a blood fluid sample containing lipoproteins other than HDLs, comprising:
contacting the sample with a sample reservoir through which the sample is distributed to one or more sample collection sites;
bringing into contact with such a sample collection site a laminate comprising (i) a reagent pad containing a reagent effective to selectively bind and remove non-HDLs from the fluid sample, and (ii) an HDL test pad having a detectable indicator of HDL cholesterol;
wherein said blood fluid sample passes through said laminate by capillary action and/or gravity through said laminate to permit measurement of HDL concentration; and
measuring the level of HDL cholesterol in said sample by detection at said HDL test pad.
31. The method of claim 30 , wherein contact between said laminate and said sample collection site is broken when a desired amount of sample has been transferred.
32. The method of claim 30 , wherein said reagent comprises a sulfonated polysaccharide.
33. The method of claim 30 , wherein at least one of said HDL test pad or said reagent pad comprises a porous polymeric membrane.
34. The method of claim 30 , wherein said reagent pad comprises multiple stacked layers, at least one of which contains a reagent effective to bind non-HDLs.
35. The method of claim 30 , wherein said measurement of HDL concentration is via optical detection.
36. The method of claim 30 , wherein said HDL test pad comprises a biosensor.
37. The method of claim 36 , wherein said biosensor is effective to electrochemically measure production of oxygen or hydrogen peroxide.