METHOD FOR DETERMINING THE CONCENTRATION OF AN ANALYTE IN A LIQUID SAMPLE USING SMALL VOLUME SAMPLES AND FAST TEST TIMES

• US 20070170054A2
• Filed: 03/05/2003
• Published: 07/26/2007
• Est. Priority Date: 11/16/2001
• Status: Active Grant

• Current Assignee: Roche Diabetes Care Inc. (Roche Holding AG)
• Original Assignee: Corange International Limited (Roche Holding AG), Roche Diagnostics Operations Incorporated (Roche Holding AG)
• Inventors: Wilsey, Christopher
• Granted Patent: US 7,276,147 B2
• Time in Patent Office: Days
• US Class Current: 204/403.10
• CPC Class Codes: C12Q 1/001 Enzyme electrodes
• CPC Class Codes: C12Q 1/006 for glucose
• CPC Class Codes: G01N 27/307 Disposable laminated or multilayered electrodes G01N27/3272 takes precedence
• CPC Class Codes: G01N 27/3272 Test elements therefor, i.e. disposable laminated substrates with electrodes, reagent and channels optical biosensors G01N33/52
• CPC Class Codes: G01N 27/3273 Devices therefor, e.g. test element readers, circuitry details not specific to biochemical electrodes G01N33/4875
• CPC Class Codes: G01N 27/3275 Sensing specific biomolecules, e.g. nucleic acid strands, based on an electrode surface reaction

Abstract

Analytes in a liquid sample are determined by methods utilizing sample volumes of less than about 1.5 μl and test times within ten seconds. The methods are preferably performed using small test strips including a sample receiving chamber filled with the sample by capillary action.

Claims

1-36. -36. (canceled)

37. A method of determining the concentration of glucose in a blood sample, comprising:

providing a disposable biosensor test strip including a capillary chamber having a depth suitable for capillary flow of blood and holding a volume of less than about 1.0 μ

l of the blood sample, a working electrode and a counter or reference electrode disposed within the capillary chamber, and a reagent proximal to or in contact with at least the working electrode, the reagent including an enzyme and a mediator, the reagent reacting with glucose to produce an electroactive reaction product;

applying a blood sample containing glucose into the capillary chamber, the capillary chamber directing capillary flow of the blood sample into contact with the reagent to cause the blood sample to at least partially solubilize or hydrate the reagent;

detecting the blood sample in the capillary chamber;

electrooxidizing or electroreducing the electroactive reaction product at the working electrode; and

within 10 seconds after said detecting, determining and providing a readout of the glucose concentration in the blood sample, said determining comprising correlating the electrooxidized or electroreduced electroactive reaction product to the concentration of glucose in the blood sample.

38. The method of claim 52 in which the capillary chamber holds a volume of between about 0.25 μ

l and about 0.4 μ

l.

39. The method of claim 37 in which said detecting comprises applying a dose-detect potential between the working and counter or reference electrodes, and recognizing a rise in current as an indication that the sample has been supplied to the capillary chamber.

40. The method of claim 37 in which the test strip includes a vent communicating with the capillary chamber to facilitate flow of the sample into the capillary chamber.

41. The method of claim 37 in which said providing comprises providing the reagent in a sufficiently small amount as to be solubilized or hydrated in a time sufficient to allow said determining and providing a readout of the glucose concentration in the sample within 10 seconds after said detecting.

42. The method of claim 37 in which said providing comprises providing a test strip including a bottom substrate, a spacing layer, and a top substrate, the spacing layer having an opening corresponding to the capillary chamber, the spacing layer substantially defining the depth of the capillary chamber.

43. The method of claim 42 in which the test strip is elongated with two opposed sides, the spacing layer comprising spaced-apart first and second portions defining a capillary chamber extending between and opening at the two opposed sides.

44. The method of claim 37 in which said providing comprises providing a mediator in its oxidized form.

45. The method of claim 44 in which the mediator reacts sufficiently rapidly as to allow said determining and providing a readout of the glucose concentration in the sample within 10 seconds after said detecting.

46. The method of claim 45 in which said providing comprises providing the reagent in a sufficiently small amount as to be solubilized or hydrated in a time sufficient to allow said determining and providing a readout of the glucose concentration in the sample within 10 seconds after said detecting.

47. The method of claim 54 in which the capillary chamber holds a volume of between about 0.25 μ

l and about 0.4 μ

l.

48. The method of claim 47 in which said detecting comprises applying a dose-detect potential between the working and counter or reference electrodes, and recognizing a rise in current as an indication that the sample has been supplied to the capillary chamber.

49. The method of claim 48 in which the test strip includes a vent communicating with the capillary chamber to facilitate flow of the sample into the capillary chamber.

50. The method of claim 49 in which said providing comprises providing a test strip including a bottom substrate, a spacing layer, and a top substrate, the spacing layer having an opening corresponding to the capillary chamber, the spacing layer substantially defining the depth of the capillary chamber.

51. The method of claim 50 in which the test strip is elongated with two opposed sides, the spacing layer comprising spaced-apart first and second portions defining a capillary chamber extending between and opening at the two opposed sides.

52. The method of claim 37 in which the capillary chamber holds a volume of less than about 0.4 μ

l.

53. The method of claim 37 in which said electroactive reaction product is capable of being electrooxidized or electroreduced at the working electrode, said determining comprising measuring the amount of electroactive reaction product electrooxidized or electroreduced, and correlating the amount of electrooxidized or electroreduced electroactive reaction product to the concentration of glucose in the blood sample.

54. The method of claim 46 in which the capillary chamber holds a volume of less than about 0.4 μ

l.

55. The method of claim 37 in which said capillary chamber has a depth of 25-200 μ

m.

94. The method of claim 37 including automatically operating the test strip and timing the reaction and analysis of the blood sample to detect the blood sample in the capillary chamber, to electrooxidize the electroactive reaction product, and to determine and provide a readout of the glucose concentration within 10 seconds of said detecting.

95. The method of claim 37 in which the test strip comprises a counter electrode, and in which the reagent is located proximal to or in contact with the working and counter electrodes.

96. The method of claim 37 in which the capillary chamber holds a volume of about 600 nL.

97. The method of claim 96 comprising determining and providing a readout of the glucose concentration within about 5 seconds after said detecting.

98. The method of claim 37 in which the capillary chamber holds a volume of between 0.25 μ

l and 0.4 μ

l.

99. The method of claim 98 comprising determining and providing a readout of the glucose concentration within about 5 seconds after said detecting.

100. The method of claim 98 in which the capillary chamber holds a volume of about 400 nL.

101. The method of claim 100 comprising determining and providing a readout of the glucose concentration within about 5 seconds after said detecting.

102. The method of claim 98 in which the capillary chamber holds a volume of about 300 nL.

103. The method of claim 102 comprising determining and providing a readout of the glucose concentration within about 5 seconds after said detecting.

104. The method of claim 37 comprising determining and providing a readout of the glucose concentration within about 8 seconds of said detecting.

105. The method of claim 104 comprising determining and providing a readout of the glucose concentration about 3.5 to about 8 seconds after said detecting.

106. The method of claim 105 comprising determining and providing a readout of the glucose concentration within about 5 seconds of said detecting.

107. The method of claim 106 comprising determining and providing a readout of the glucose concentration within about 4 seconds of said detecting.

108. The method of claim 105 comprising determining and providing a readout of the glucose concentration about 5 seconds after said detecting.

109. The method of claim 105 comprising determining and providing a readout of the glucose concentration about 4 seconds after said detecting.

56-93. -93. (canceled)

110. A method of determining the concentration of glucose in a blood sample, comprising:

providing a disposable biosensor test strip including a capillary chamber having a depth suitable for capillary flow of blood and holding a volume of less than about 1.0 μ

l of the blood sample, a working electrode and a counter or reference electrode disposed within the capillary chamber, and a reagent proximal to or in contact with at least the working electrode, the reagent including an enzyme and a mediator, the reagent reacting with glucose to produce an electroactive reaction product;

applying a blood sample containing glucose into the capillary chamber, the capillary chamber directing capillary flow of the blood sample into contact with the reagent to cause the blood sample to at least partially solubilize or hydrate the reagent;

detecting the blood sample in the capillary chamber;

electrooxidizing the electroactive reaction product at the working electrode; and

within 10 seconds after said detecting, determining and providing a readout of the glucose concentration in the blood sample, said determining comprising correlating the electrooxidized electroactive reaction product to the concentration of glucose in the blood sample.

111. The method of claim 110 in which the capillary chamber holds a volume of about 600 nL.

112. The method of claim 111 comprising determining and providing a readout of the glucose concentration within about 5 seconds after said detecting.

113. The method of claim 110 in which the capillary chamber holds a volume of between 0.25 μ

l and 0.4 μ

l.

114. The method of claim 113 comprising determining and providing a readout of the glucose concentration within about 5 seconds after said detecting.

115. The method of claim 113 in which the capillary chamber holds a volume of about 400 nL.

116. The method of claim 115 comprising determining and providing a readout of the glucose concentration within about 5 seconds after said detecting.

117. The method of claim 113 in which the capillary chamber holds a volume of about 300 nL.

118. The method of claim 117 comprising determining and providing a readout of the glucose concentration within about 5 seconds after said detecting.

119. The method of claim 110 comprising determining and providing a readout of the glucose concentration within about 8 seconds of said detecting.

120. The method of claim 119 comprising determining and providing a readout of the glucose concentration about 3.5 to about 8 seconds after said detecting.

121. The method of claim 120 comprising determining and providing a readout of the glucose concentration within about 5 seconds of said detecting.

122. The method of claim 121 comprising determining and providing a readout of the glucose concentration within about 4 seconds of said detecting.

123. The method of claim 120 comprising determining and providing a readout of the glucose concentration about 5 seconds after said detecting.

124. The method of claim 120 comprising determining and providing a readout of the glucose concentration about 4 seconds after said detecting.

125. The method of claim 110 in which the reagent is dry, and the capillary chamber directs capillary flow of the blood sample into contact with the dry reagent to cause the blood sample to at least partially solubilize or hydrate the dry reagent.

126. The method of claim 125 in which the dry reagent comprises a reagent that is applied wet and dried of solvent.

127. The method of claim 110 in which the capillary chamber has a depth of 25-200 μ

m.

128. The method of claim 110 in which said providing comprises providing the reagent in a sufficiently small amount as to be solubilized or hydrated in a time sufficiently fast to allow said determining and providing a readout of the glucose concentration in the blood sample within 10 seconds of said detecting.

129. The method of claim 128 in which the mediator reacts sufficiently rapidly as to allow determining and providing a readout of the glucose concentration in the blood sample within 10 seconds of said detecting.

130. The method of claim 129 in which the mediator is readily-reversible.

131. The method of claim 110 including automatically operating the test strip and timing the reaction and analysis of the blood sample to detect the blood sample in the capillary chamber, to electrooxidize the electroactive reaction product, and to determine and provide a readout of the glucose concentration within 10 seconds of said detecting.

132. The method of claim 131 in which said automatically operating comprises connecting the test strip to an external testing apparatus prior to said detecting, the testing apparatus automatically detecting the blood sample in the capillary chamber, electrooxidizing the electroactive reaction product, determining the glucose concentration, and providing a readout of the glucose concentration within 10 seconds of said detecting.

133. The method of claim 110 in which the working electrode and the counter or reference electrode are coplanar.

134. The method of claim 110 comprising measuring the current and correlating the measured current to the glucose concentration.

135. The method of claim 110 in which said detecting comprises applying a drop-detect potential across the working and counter or reference electrodes.

136. The method of claim 135 in which said detecting comprises applying a drop-detect potential across the working and counter or reference electrodes prior to and separate from said determining.

137. The method of claim 136 in which said detecting comprises applying a drop-detect potential across the working and counter or reference electrodes and recognizing a rise in current as an indication that the blood sample has been applied into the capillary chamber.

138. The method of claim 136 which includes reapplying a potential across the working and counter or reference electrodes, after a delay period during which no potential is applied, to electrooxidize the electroactive reaction product at the working electrode.

139. The method of claim 110 in which said providing comprises providing a test strip including a bottom substrate, a spacing layer, and a top substrate, the spacing layer having an opening corresponding to the capillary chamber, the spacing layer substantially defining the depth of the capillary chamber.

140. The method of claim 110 in which said reacting produces a reduced form of the mediator.

141. The method of claim 110 comprising measuring the amount of the electrooxidized electroactive reaction product and correlating the amount to the concentration of glucose in the blood sample.

142. The method of claim 110 comprising applying a potential of 100-500 mV across the working electrode and the counter or reference electrodes.

143. The method of claim 110 in which the test strip comprises a counter electrode, and in which the reagent is located proximal to or in contact with the working and counter electrodes.