EP0735369A1
Expired / Lapsed
EP
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Chemical timer for a direct-reading reagent test strip
Assignee: LifeScan Inc
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Filing: 1996-03-26
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Granted: —
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Expires: 2016-03-26
Abstract
Abstract A chemical timer for a direct-reading reagent test strip changes color a predetermined time after a biological fluid is applied to the strip. The strip measures the concentration of an analyte in the fluid. The timer is a dry coating of an indicator, a reagent that when hydrated can react with glucose to change the color of the indicator, an inhibitor to inhibit the change in color of the indicator, and glucose. Preferably, the reagent and glucose are present in excess in the coating, and the time it takes for the timer color to change can be controlled by the inhibitor concentration.
Inventors
- 👤 Ernest J. Kiser
- 👤 Michael F. Tomasco
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-23 09:37
CPC Classifications
C; C12; C12Q; C12Q1/00; C12Q1/54; G; G01; G01N; G01N33/00; G01N33/48; G01N33/50; G01N33/52; G01N33/521; G01N33/523; G01N33/525; G01N33/526
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
112 words
A chemical timer for a direct-reading reagent test strip for measuring the concentration of an analyte in a biological fluid that is applied to the strip, the timer comprising a dry coating of a) an indicator composition, b) a reagent that, when hydrated, is capable of reacting with glucose to change the color of the indicator, c) an inhibitor to inhibit the change in color of the indicator, and d) glucose, in which the inhibitor and glucose concentrations in the dry coating are selected so that the glucose, over a predetermined time after the biological fluid is applied to the strip, reacts with the reagent to change the color of the indicator.
Claim 2
Dependent Claim
11 words
The timer of claim 1 in which the analyte is glucose.
Claim 3
Dependent Claim
15 words
The timer of claim 1 or claim 2 in which the biological fluid is blood.
Claim 4
Dependent Claim
83 words
The timer of any one of claims 1 to 3 in which the indicator is (a) 3-methyl-2-benzothiazolinone hydrazone hydrochloride (MBTH) combined with 3,3-dimethylaminobenzoic acid (DMAB); (b) MBTH combined with 3,5-dichloro-2-hydroxybenzene-sulfonic acid (DCHBS); (c) 4-aminoantipyrene (4-AAP) and 5-oxo-1-(p-sulfophenyl)-2-pyrazoline-3-carboxylic acid (OPSP);(d)4-AAP and N-(m-tolyl)diethanolamine (NDA); (e) 2,2'-azino-di-(3-ethylbenzthiazoline) sulfonic acid (ABTS); (f) 4-AAP and 4-methoxynaphthol; (g) pyrogallol red (PGR); (h) bromopyrogallol red (BPR); (i) acid green 25 (AG); or (j) [3-methyl-2-benzothiazolinone hydrazone] N-sulfonyl benzenesulfonate monosodium (MBTHSB) combined with 8-anilino-1-naphthalene sulfonic acid ammonium (ANS) and is preferably MBTHSB-ANS.
Claim 5
Dependent Claim
22 words
The timer of any one of claims 1 to 4 in which the reagent comprises an oxidase enzyme, such as glucose oxidase.
Claim 6
Dependent Claim
17 words
The timer of any one of claims 1 to 5 in which the inhibitor comprises ascorbic acid.
Claim 7
Dependent Claim
33 words
A direct-reading reagent test strip for measuring concentration of an analyte in a biological fluid that is applied to said strip, comprising the chemical timer of any one of claims 1 to 6.
Claim 8
Independent Claim
109 words
A method for preparing a chemical timer for a direct-reading reagent test strip for measuring the concentration of an analyte in a biological fluid that is applied to the strip, comprising the steps of a) coating onto a porous membrane a solution of a reagent that, when hydrated, is capable of reacting with glucose b) drying the coating to form a first layer c) applying onto the first layer a second layer that contains (i) glucose (ii) an indicator that can react with the reaction product of the reagent and glucose to cause a color change, and (iii) an inhibitor to inhibit the change in color of the indicator.
Claim 9
Dependent Claim
17 words
The method of claim 10 in which the analyte is glucose and the reagent comprises glucose oxidase.
Claim 10
Independent Claim
106 words
A method for measuring the concentration of an analyte in a biological fluid comprising the steps of (a) applying the fluid to a test strip that comprises (i) a plurality of result segments that each change color when contacted with fluid containing at least a predetermined amount of analyte, different from the amount of analyte that causes a change in color of the other segments and (ii) a timer segment that changes color after a time whose duration is substantially independent of the amount of analyte in the fluid and (b) observing the result segment that has changed color last when the timer segment changes color.
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