Device for determining the presence of organic materials by colorimetric indication

Abstract: A test card incorporates a colorimetric indicator test to determine the presence of a minute amount of a specific substance in a liquid medium. The test card includes top and bottom sheets adhesively secured to an intermediate frame member which, together with the top and bottom sheets, defines a filter chamber having a flat filter therein which incorporates a test portion. The test portion of the filter has a binding substrate to which antibodies of the specific substance have been bound. This binding substrate is in communication with a test port. In the method of the invention a substance to be tested is administered through the test port and contains an unknown amount of antigen. After the sample is administered an aqueous solution of enzyme labelled antigen is administered and, subsequently, a liquid substrate is added to cause a color change in the filter below the test port inversely proportional to the amount of antigen contained in the sample administered at the test port.

Description: The invention relates to a colorimetric indicator testing device for determining the presence of a specific substance in a liquid medium comprising: a housing including a top wall, a bottom wall and side edges, a filter chamber in said housing, a flat elongated filter body located in said filter chamber, said filter body having control and test portions juxtaposed respectively to control and test ports in said top wall, barrier means in said housing located between said control and test portions to isolate said portion from one another. Such a device is disclosed in GB-A-2180645. The wide spread use of a wide variety of substances in an equally variety of environments has made repeated testing for the specific substances necessary in order to control, for example, antibiotic dosages or to determine whether fields which have been treated with various types of organic insecticides are safe for field workers to enter. Conventional methods of testing entail the drawing or making of a sample of the substance to be tested. For instance, where paraquat is utilized in spraying vegetation, a sample of the vegetation which has been spread is taken to the laboratory and a liquid suspension of the paraquat is made which is then subjected to a series of conventional laboratory test to determine whether the paraquat has been dissipated or whether the amount remaining is so small as to render it safe for workers to enter the paraquat-sprayed field. Naturally, the necessity for remote testing of the specimens of the substance entails consumption of time which delays the harvesting or other necessary treatment of crops. Similarly, where patients are subjected to large doses of antibiotics, such as neomycin, gentamicin and the like, it is customary to draw blood and to take the blood samples to a hospital laboratory or other laboratories which then make the requisite test necessary to determine the amount of antibiotic present in the blood of the patient. Such remote testing, once again, delays immediate action upon the part of the hospital staff to curb or enlarge the antibiotic dosages as a result of the test indications. To eliminate the delays incident to conventional testing for various types of organic chemicals, applicant developed the portable colorimetric testing device according to said GB-A-2180645. This device can be embodied in a card which is no larger than the plastic credit card conventionally carried in most individuals' wallets. By the utilization of this card to detect specific substances, it becomes feasible to perform in situ tests at the immediate location where the substances are to be sampled. In the device according to GB-A-2180645 the control and test portions are constituted by elongated fingers protuding from the body of the filter and said barriers are interspersed between said fingers. The flow of fluids away from the reaction ports is possible in one direction only. This leads to a rather slow wicking. The object of the invention is the provision of a colorimetric testing device of the character as mentioned in the preamble, which leads to faster wicking and enables the use of a smaller hole for reagent reaction requiring less reagents. An other object of the invention is the provision of a colorimetric testing device presenting more desirable manufacturing economics since more tests can be placed on the same device. According to the invention said control and test portions of the filter body have liquid carrier means disposed in at least two directions leading from each of said ports. Preferably the barrier means are formed by raised islands on the bottom wall. Other objects and advantages of the invention will be apparent from the following specification and the accompanying drawings. Figures 1 and 2 are exploded views and a top view of two embodiments of the invention. Referring to the drawings, we show a colorimetric testing device 10 incorporated in a test card which, as previously mentioned, is approximately the same size as a conventional credit card and of approximately the same bulk. While we show the colorimetric testing device as incorporated, in this embodiment of the invention, in a card, it will, of course, be obvious to those skilled in the art that various embodiments of the invention can be fabricated in different forms without departing from the teachings of the invention. The test card is of generally rectangular configuration and is constituted by a top sheet 14 fabricated from a synthetic plastic material, such as vinylchloride. The top sheet 14 is adhesively secured to an intermediate frame member 18 which is stamped or otherwise formed from relatively rigid, thin plastic material such as vinylchloride and which incorporates an elongated rectangular opening. Located in the elongated rectangular opening of the frame member 18, which serves as the filter chamber of the device 10, is a flat elongated filter body, said filter body being formed from compacted glass fibers or the like. The filter can be fabricated from a wide variety of filter material and formed from any number of depth-type planar materials capable of entrapping suspension elements or particulates. Exemplary of such a material is glass microfiber material which is available in a range of porosities. An inherent characteristic of the filter material utilized must be that the filter porosities are interconnected in the plane of the filter. A conventional filter which is capable of entrapping formed suspension elements of particulates, but which is not suitable for the practice of the invention is a planar membrane filter which has porosities connecting its opposite surfaces but offers no pathway for lateral flow generally parallel to and between the surfaces. The filter body has the provision within it of showing at least two sets of projectile fingers 32 leading from the reaction ports 40, 42 and 44. This provides so called bi-directional flow of fluids away from the reaction ports. Raised islands 48 separate the reaction sites from one another and vent holes 15 allow proper venting. The filter body is inserted in the opening of the frame member (18) constituting the filter chamber, and the top sheet 14 is adhesively secured to the perimeter of the frame member 18. After physical assembly of the test kit, the binding substrates are deposited upon the test and fingers 32 through the ports 40, 42 and 44 respectively. Such binding substrates, of course, must conform to the particular tests sample which is the subject of the test. Typical bacterial binding substrates are staphylococcus aureous A and analogous binding bacteria. It is also conceivable that solid substrates, such as microspheroids fabricated from rubber or glass, may be utilized in the filter tests and fingers 32. After the dosing of the fingers 32, the requisite antibodies for the antigen being tested are deposited on the binding substrates of the fingers and maximum saturation of the binding substrate is achieved. After the antibodies have been bound on the binding substrate, the test kit is ready for use. Of course, the test kit is appropriately labelled with the name of the test in which it is to be utilized. Consequently, a large number of assembled kits can be maintained in inventory and the substrate antibody combination applied through ports 40, 42 and 44 when the need for the particular test arises. The fluids can flow now in two directions instead of one, leading to faster wicking. This also enables the use of a smaller hole for the reagent reaction requiring less reagents. One obtains more flexibility from a card of the present embodiment in that there is a more focused reaction site and the potential of adding a greater volume of liquid material since the wicking action occurs over two reservoirs instead of the one present in the uni-directional flow card. We have found also that there is a subsequent lower background reading when utilizing a bi-directional flow card of the type as shown in figure 1. In some cases it might be desirable to have an added reservoir retention. For example, when several reactions are run on one card of the type shown in figure 2, added reservoirs pads 50, may be placed under the filter pad 30 through ports 52 so as to permit the retention of a greater volume of liquid. The present card also presents more desirable manufacturing economies than the uni-directional flow card since may more tests can be placed on the same card. The card may be hard or soft. With the same wicking as is obtained in two ports, it is possible to use six or more ports because the double flow gives rise to a more even distribution of diffused liquid. Referring now to figure 1, it will be observed that filter pad 30 is configured in a way such that projectile fingers 32 are bi-directional with the neck portion thereof being directly under the reaction ports 40, 42 and 44 in top layer 14. It will now be observed that there are two reservoir masses leading from the projectile fingers 32 which communicate with the projectile fingers supplying two separate means to aid in the more rapid wicking of liquid away from the reaction site. Beneath filter 30 is the plastic template 20 which meets the filter and contains isolation portions 48. These portions separate the reaction chambers in the bi-directional flow mode. It could be preferred under certain circumstances to increase the number of fingers and reaction ports per card to as many as six or more. For the sake of convenience a diagram has been shown at figure 2 of this multi port bi-directional flow embodiment with the operation being self-explanatory.

Claims: Colorimetric indicator testing device for determining the presence of a specific substance in a liquid medium comprising: a housing including a top wall, a bottom wall and side edges, a filter chamber in said housing, a flat elongated filter body (30) located in said filter chamber, said filter body having control and test portions juxtaposed respectively to control and test ports (40, 42, 44) in said top wall, barrier means (48) in said housing located between said control and test portions to isolate said portion from one another, characterized in that said control and test portions of the filter body have liquid carrier means disposed in at least two directions leading from each of said ports. Colorimetric indicator testing device according to claim 1, characterized in that said barrier means are formed by raised islands (48) in the bottom wall.

Inventors: KELTON ARDEN ALLAN, WIE SIONG IK, KELTON, ARDEN ALLAN, WIE, SIONG IK
Applicants: ENVIRONMENTAL DIAGNOSTICS INC, ENVIRONMENTAL DIAGNOSTICS, INC.
Application year: 1989
Main classification: G01N33
IPC codes: G01J3, G01N33, G01N31