Claims
- 1. A diagnostic apparatus comprising a one piece open celled porous substrate defining a top surface and a lower reservoir section and a top layer, said top layer being microporous and biochemically inert, said reservoir portion being macroporous and being in capillary communication with the micropores of said top surface, wherein said micropores are of a size sufficient to trap, in or on the top layer, microspheres of a diameter of 5 microns or less, the pores in said reservoir portion having an average size of at least 20 microns in diameter, said reservoir portion having a substantially greater volume than said top layer.
- 2. A diagnostic apparatus as recited in claim 1, wherein said substrate is contained within a container, said container having a top opening exposing said top surface and having a closed bottom opposite said top opening.
- 3. A diagnostic apparatus as recited in claim 1, wherein microspheres are located in or on said top surface.
- 4. A diagnostic apparatus as recited in claim 1, wherein said substrate comprises sintered particles of synthetic resin and a microporous matrix cast into the pores of said substrate at said top surface.
- 5. A diagnostic apparatus as recited in claim 4, wherein said top layer comprises particles which are smaller than the particles which comprise said reservoir portion.
- 6. A diagnostic apparatus as recited in claim 4, wherein said microporous matrix is formed from a casting solution comprising from about 44.0 to 45.4 parts by weight of butanol, from about 41.9 to 43.3 parts by weight of acetone, from about 6.5 to 9.1 parts by weight of nitrocellulose, from about 0.8 to 1.1 parts by weight of cellulose acetate, and from about 3.9 to 4.0 parts by weight of water.
- 7. A diagnostic apparatus comprising a one piece open celled pore substrate having a microporous biochemically inert top layer and a macroporous reservoir portion below said top layer, said top layer having micropores of the size to entrap microspheres of a diameter of 5 um or less on or in said top layer when applied to said top layer in a liquid suspension, the pores in said reservoir portion having an average pore size of at least 20 microns in diameter and being in capillary communication with the micropores of said top layer, said reservoir portion having a substantially greater volume than said top layer.
- 8. A diagnostic apparatus as recited in claim 7, further comprising a container containing said substrate and defining an opening exposing the surface of said top layer and having a closed bottom opposite said opening.
- 9. A diagnostic apparatus as recited in claim 7, wherein microspheres are entrapped in or on said top layer.
- 10. A diagnostic apparatus as recited in claim 7, wherein said substrate comprises sintered particles of synthetic resin in said top layer and said reservoir portion and wherein said top layer comprises particles which are smaller than the particles in said reservoir portion.
- 11. A diagnostic apparatus as recited in claim 10, wherein a microporous matrix is cast into the pores of said top layer adjacent to the top surface thereof.
- 12. A diagnostic apparatus as recited in claim 11, wherein said microporous matrix is formed from a casting solution comprising from about 44.0 to 45.4 parts by weight of butanol, from about 41.9 to 43.3 parts by weight of acetone, from about 6.5 to 9.1 parts by weight of nitrocellulose, from about 0.8 to 1.1 parts by weight of cellulose acetate, and from about 3.9 to 4.0 parts by weight of water.
- 13. A diagnostic apparatus as recited in claim 10, wherein said top layer of sintered particles is formed by distributing said smaller particles in a layer and applying a compressive force to said layer to reduce the size of the interstices between said smaller particles and then sintering said smaller particles together.
- 14. A diagnostic apparatus as recited in claim 7, wherein said substrate comprises particles of synthetic resin and a microporous matrix cast within the pores of said top layer adjacent to the top surface of said layer.
- 15. A diagnostic apparatus comprising a one piece open celled porous substrate defining a top layer and said top surface and a lower reservoir section and a top layer, said top surface being microporous, said reservoir portion being macroporous and being in capillary communication with the micropores of said top layer, and microspheres located in or on said top layer wherein said micropores are of a size sufficient to trap, in or on the top layer, microspheres of a diameter of 5 microns or less, the pores in said reservoir portion having an average size of at least 20 microns in diameter, said reservoir portion having a substantially greater volume than said top layer.
BACKGROUND OF THE INVENTION
The present application is a continuation-in-part of pending U.S. application Ser. No. 74,968, filed July 17, 1987 now abandoned.
The present invention relates to an improved diagnostic testing system of the type in which microspheres or other small particles are immobilized at or near the top surface thereof.
A number of immunoassay systems have been developed utilizing immunologic technology. In these systems, the presence of an antigen in a test sample is detected by causing the antigen to bind to antibodies in a selected testing medium and then detecting the presence of the antigen in the testing medium. In a recently developed system, the testing procedure and the time to carry out the testing process has been substantially reduced so as to make it convenient to carry out the immunoassay process in a doctor's office or by a patient at home.
The prior art system, as shown in FIG. 1, comprises a container 11, housing an absorbent cylinder 13, which serves as a reservoir. On top of the reservoir is a porous plastic disk 15 on which is supported a porous membrane 17, usually separated from the porous plastic disk 15 by a porous contact pad 19. In the immunoassay process, antibodies specific to the antigen being detected are deposited on the membrane 17 by first bonding the antibodies or adsorbing the antibodies on microspheres of a synthetic resin such as polystyrene or latex and then depositing these microspheres in or on the membrane by passing liquid in which the microspheres are suspended through the membrane. A test sample to be tested for the presence of the suspect antigen is poured on the membrane 17 and is drawn through the membrane 17 relatively rapidly by capillary action of the reservoir 13 in combination with the porous plastic disk 15 and the contact pad 19. If the suspect antigen is in the test sample, it will bind to the antibodies deposited on or in the membrane. Following this step, liquid containing labeled antibodies specific to the suspect antigen is poured onto the membrane and is drawn through the membrane into the reservoir 13 by capillary action. If the antigen has been extracted from the test sample and retained in or on the membrane, the labeled antibodies will bind to the antigen and thus remain in or on the membrane 17. The application of the labeled antibody to the membrane will usually be followed by a rinsing step to remove unbound labeled antibody. This rinsing step is then followed by a step of causing the labeled antibody to exhibit its presence. In the case of an enzyme label, this last step is carried out by addition of a solution of a color-forming agent which reacts with the enzyme as the solution passes through it. As each liquid is passed through the membrane it is absorbed by the reservoir and the reservoir must be large enough to hold all of the volume of the test specimen, the labeled antibody solution, the rinse solution and the color-forming solution.
To obtain an accurate indication of the presence or absence of the antigen, the system must cause an even, consistent flow of the various liquids which are passed through the membrane. In order to achieve this even flow, contact between the various components of the system must be maintained. Any gaps between any two of the components will create pools of stagnant liquid and interfere with the capillary action drawing the liquid into the reservoir. This interference leads to erroneous or vague test results. Thus, when assembling the components of the system, great care must be taken to avoid trapping any particulate matter between the components, which particulate matter would create gaps between the components. The material of the membrane is available only as relatively large flat sheet and they must be cut into disks for use in the system. The assembly of the components is difficult because both the membrane and the contact pad are flimsy and manual assembly is usually required.
The system of the present invention is designed to overcome the above described problems in the prior art system. In accordance with the present invention, a one-piece porous substrate is provided in the container and serves both to extract the target substance in or on a top layer thereof with the remainder of the pore structure of the substrate serving as a reservoir. The pores in the top surface of the porous substrate are microscopic for entrapment of macroscopic particles such as microspheres. The pores in all but the thin top layer of the substrate have a much greater pore size and this portion of the substrate with the larger pores acts as a reservoir for the liquids to be passed through the top layer. Because the reservoir and layer in or on which the microspheres are entrapped are of one piece, the problems of assembly and the potential gaps between the components of the prior art system are avoided.
The invention also includes a method that produces a desired diagnostic system by casting a microporous matrix in surfaces of a plurality of macroporous slugs. The method includes the steps of selecting a casting apparatus that defines openings for receiving the slugs and wells that are adjacent to the openings, positioning the slugs in the openings with the surfaces facing upward, the surfaces being positioned adjacent to the wells, and dispensing a casting solution into the wells so that the solution contacts the surfaces. At least a portion of the solution is then allowed to wick into the slugs and harden, whereby the microporous matrix is cast in the surfaces.
US Referenced Citations (14)
Foreign Referenced Citations (8)
| Number |
Date |
Country |
| 711286 |
Jul 1968 |
BEX |
| 74161 |
Dec 1944 |
CSX |
| 207721 |
Jan 1987 |
EPX |
| 2421035 |
Nov 1974 |
DEX |
| 2502508 |
Oct 1982 |
FRX |
| 55-132605 |
Oct 1980 |
JPX |
| 60-89757 |
May 1985 |
JPX |
| 8505451 |
Dec 1985 |
WOX |
Continuation in Parts (1)
|
Number |
Date |
Country |
| Parent |
74968 |
Jul 1987 |
|
Patent Grant
5073344
