Assay timed by electrical resistance change and test strip
First Claim
1. An assay for determining an analyte in a liquid sample, said assay comprising:
- applying a volume of the sample to a target location on a bibulous matrix, wherein the matrix comprises one or more dried reagents which in the presence of the analyte initiate time-dependent production of an optically detectable signal within the matrix;
measuring a change in electrical resistance across the target location which results from the application of liquid sample;
initiating a timing cycle when a lowering of electrical resistance is first measured; and
measuring the production of said optically detectable signal within the matrix at one or more times during the timing cycle.
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Accused Products
Abstract
Assays for liquid analytes are performed on a bibulous matrix containing dried reagents which produce a visibly detectable reaction product. Application of liquid sample to the bibulous matrix is detected by measuring a drop in resistance across the matrix. A preferred test article for performing the method includes the matrix and a pair of spaced-apart electrodes in electrical contact with a reaction zone on the matrix. The test article is used in combination with a detection unit having means for probing the electrodes to determine when electrical resistance in the matrix has decreased. The assay methods and apparatus are particularly useful for performing enzyme assays where signal developed as a function of time is critical.
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Citations
31 Claims
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1. An assay for determining an analyte in a liquid sample, said assay comprising:
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applying a volume of the sample to a target location on a bibulous matrix, wherein the matrix comprises one or more dried reagents which in the presence of the analyte initiate time-dependent production of an optically detectable signal within the matrix; measuring a change in electrical resistance across the target location which results from the application of liquid sample; initiating a timing cycle when a lowering of electrical resistance is first measured; and measuring the production of said optically detectable signal within the matrix at one or more times during the timing cycle. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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- 11. An improved enzyme assay of the type wherein a liquid sample suspected of containing the enzyme is applied to a bibulous matrix-containing reagents which result in production of an optically detectable signal over time, wherein the improvement comprises measuring a change in electrical resistance within the matrix resulting from application of the liquid sample and optically detecting the production of signal at one or more times after the electrical resistance change is first measured.
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15. A test article comprising:
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a bibulous matrix; one or more dried reagents which are present within the matrix and which, when wetted by a liquid sample, initiate an optically detectable chemical reaction with an analyte present in the sample; and a pair of spaced-apart electrodes proximate a sample target location of the matrix, wherein the electrodes are disposed so that application of the liquid sample to the target location will lower electrical resistance between the electrodes. - View Dependent Claims (16, 17, 18, 19, 20, 21, 22, 23)
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24. A test article comprising:
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a bibulous matrix; one or more dried reagents which are dispersed within the matrix and which, when wetted by a liquid sample, initiate an optically detectable enzymatic reaction with an enzyme analyte present in the sample; and a pair of spaced-apart metal strips attached to a surface of the matrix to define a sample target location therebetween, whereby application of the liquid sample to the target location will lower electrical resistance between the metal strips. - View Dependent Claims (25, 26, 27, 28, 29, 30, 31)
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Specification