Assay device and method using a signal-modulating compound

Claim 1

An assay test strip for use in assaying the concentration of an analyte in an aqueous fluid sample, where the analyte is one which can serve as a substrate for an oxidase enzyme, with the generation of H 2 O 2 comprising: (a) an absorbent matrix effective to absorb a volume of said sample; (b) analyte-reaction reagents embedded in the matrix, including (i) an analyte-specific oxidase enzyme effective to react with analyte present in such a sample to produce H 2 O 2 ; (ii) a peroxidase enzyme; (iii) a primary substrate which can be converted from a reduced to an oxidized form by the peroxidase enzyme in the presence of H 2 O 2 , and (iv) a secondary substrate capable of reacting with the oxidized form of the primary substrate to form an analyte-dependent amount of a colored reaction product, and (c) a trapping compound embedded in the matrix, which trapping compound is effective to (i) compete with the secondary substrate for reaction with the oxidized form of the primary substrate to produce a substantially colorless product, and (ii) reduce the amount of colored reaction product generated by a given amount of analyte in proportion to the relative amounts of trapping compound and secondary substrate present in the matrix.

Claim 12

A method for assaying the concentration of an analyte in an aqueous fluid sample, where the analyte is one which can serve as a substrate for an oxidase enzyme, with the generation of H 2 O 2 , comprising: (a) adding a volume of the fluid sample to an absorptive matrix that contains (i) analyte-reaction reagents, including an analyte-specific oxidase enzyme effective to react with analyte present in such a sample to produce H 2 O 2 , a peroxidase enzyme, a primary substrate which can be converted from a reduced to an oxidized form by the peroxidase enzyme in the presence of H 2 O 2 , and a secondary substrate capable of reacting with the oxidized form of the primary substrate to form an analyte-dependent amount of a colored reaction product; included in the absorptive matrix is a trapping compound which is effective to compete with the secondary substrate for reaction with the oxidized form of the primary substrate, to produce a substantially colorless product, colored reaction product generated by a given amount where the amount of trapping compound includes in the matrix is such as to reduce the analyte-dependent amount of colored reaction product formed: (b) by said adding, reacting the analyte with the analyte-specific oxidase enzyme, whereby H 2 O 2 generated by said reacting is utilized, in the presence of peroxidase, to generate said colored and colorless reaction products, in proportion to the relative concentrations of secondary substrate and trapping compound present in the matrix; and (c) determining the amount of colored reaction product formed in the matrix.

Claim 13

A method for assaying the concentration of an analyte in an aqueous fluid sample, where the analyte is one which can serve as a substrate for an oxidase enzyme, with the generation of H 2 O 2 , comprising: (a) adding a volume of the fluid sample to an absorptive matrix that contains (i) analyte-reaction reagents, including an analyte-specific oxidase enzyme effective to react with analyte present in such a sample to produce H 2 O 2 , a peroxidase enzyme, a primary substrate which can be converted from a reduced to an oxidized form by the peroxidase enzyme in the presence of H 2 O 2 , and a secondary substrate capable of reacting with the oxidized form of the primary substrate to form an analyte-dependent amount of a colored reaction product; included in the absorptive matrix is a trapping compound which is effective to compete with the secondary substrate for reaction with the oxidized form of the primary substrate, to produce a substantially colorless product, colored reaction product generated by a given amount where the amount of trapping compound includes in the matrix is such as to reduce the analyte-dependent amount of colored reaction product formed: (b) by said adding, reacting the analyte with the analyte-specific oxidase enzyme, whereby H 2 O 2 generated by said reacting is utilized, in the presence of peroxidase, to generate said colored and colorless reaction products, in proportion to the relative concentrations of secondary substrate and trapping compound present in the matrix; and (c) determining the amount of colored reaction product formed in the matrix.