Method for assaying coagulation in fluid samples
This invention is a disposable cartridge for use at the patient side to perform traditional coagulation assays on fresh whole blood or blood derivative samples. The cartridge, in use with an electronic analyzer allows a fluid sample to be metered and quantitatively mixed with reagents which activate the coagulation cascade. An artificial substrate for thrombin, the enzyme whose action results in clot formation is also provided. Clot formation is subsequently detected using a microfabricated sensor also housed within the cartridge which detects electrochemically the product of the thrombin reaction upon the synthetic substrate.
1. A method of assaying an enzyme in a sample of blood or blood derivative by detecting an electroactive reaction product thereof, comprising the steps of:
introducing the sample into a cartridge which includes an analysis location,
metering a portion of the sample in a holding chamber terminating in a capillary stop,
moving the metered sample through the capillary stop to the analysis location,
mixing the metered sample with reagent at the analysis location,
allowing the enzyme to react with the reagent to form the electroactive reaction product in the sample,
positioning the sample at an amperometric sensor in the analysis location, and
detecting the electroactive reaction product of the enzyme reaction using the amperometric sensor, wherein the electroactive reaction product may be correlated to the amount of enzyme in the sample of blood.
2. The method of claim 1 , wherein the enzyme is selected from the group consisting of factor VII, factor VIII, factor IX, factor X, factor XI, factor XII, and thrombin.
3. The method of claim 1 , wherein the enzyme is thrombin.
4. The method of claim 1 , wherein the enzyme is selected from the group consisting of glucose oxidase, lactate oxidase, and other oxidoreductases, dehydrogenase based enzymes, alkaline phosphatase and other phosphatases, and serine proteases.
5. The method of claim 1 , wherein the reagent comprises a water-soluble polymer, gelatin, agarose, a polysaccharide, polyethylene glycol, polyglycine, a saccharide, sucrose, an amino acid, glycine, a buffer salt, sodium phosphate, HEPES buffer, or a dye molecule.
6. The method of claim 1 , wherein the reagent comprises celite, kaolin, diatmoaceous earth, clay, silicon dioxide ellagic acid, natural thromboplastin, recombinant thromboplastin, phospholipid, or mixtures thereof.
7. The method of claim 1 , wherein the reagent comprises a substrate comprising a tosyl-glycyl-prolinyl-arginyl-, H-D-phenylalanyl-pipecolyl-, or benzyl-phenylalanyl-valyl-arginyl-moiety attached to an N-phenyl-p-phenylenediamine or N-[pmethoxyphenyl-]-p-phenylenediamine moiety.