Electrochemical biosensor test strip

Abstract

An electrochemical biosensor test strip with four new features. The test strip includes an indentation for tactile feel as to the location of the strips sample application port. The sample application port leads to a capillary test chamber, which includes a test reagent. The wet reagent includes from about 0.2% by weight to about 2% by weight polyethylene oxide from about 100 kilodaltons to about 900 kilodaltons mean molecular weight, which makes the dried reagent more hydrophilic and sturdier to strip processing steps, such as mechanical punching, and to mechanical manipulation by the test strip user. The roof of the capillary test chamber includes a transparent or translucent window which operates as a “fill to here” line, thereby identifying when enough test sample (a liquid sample, such as blood) has been added to the test chamber to accurately perform a test. The test strip may further include a notch located at the sample application port. The notch reduces a phenomenon called “dose hesitation”.

Description

[0001]Notice: More than one reissue application has been filed for the reissue of U.S. Pat. No. 5,997,817. The reissue applications are application Ser. Nos. 10 / 692,031 (the present application), 10 / 008,788, 10 / 409,721 and 10 / 693,305, all of which are divisional reissues of U.S. Pat. No. 5,997,817.FIELD OF THE INVENTION[0002]This invention relates to a biosensor and its use in the detection or measurement of analytes in fluids.BACKGROUND OF THE INVENTION[0003]The prior art includes test strips, including electrochemical biosensor test strips, for measuring the amount of an analyte in a fluid.[0004]Particular use of such test strips has been made for measuring glucose in human blood. Such test strips have been used by diabetics and health care professionals for monitoring their blood glucose levels. The test strips are usually used in conjunction with a meter, which measures light reflectance, if the strip is designed for photometric detection of a dye, or which measures some electri...

AI Technical Summary

Benefits of technology

[0010]The first new feature is an indentation along one edge of the test strip for easy identification of the sample application port for vision impaired persons or for use in zero or low lighting conditions.

[0011]The test strip has a capillary test chamber, and the roof of the test chamber includes the second new feature of the biosensor test strip. The second new feature is a transparent or translucent window which operates as a “fill to here” line, thereby identifying when enough test sample (a liquid sample, such as blood) has been added to the test chamber to accurately perform a test. The window defines the minimum sample amount, or dose, required to accurately perform a test, and, therefore, represents a visual failsafe which reduces the chances of erroneous test results due to underdosing of a test strip.

[0012]The length and width of the window are shorter than the length and width of the capillary test chamber. The window is dimensioned and positioned so that it overlays the entire width of the working electrode and at least about 10% of the width of the counter or reference electrode of the biosensor test strip. Preferably, the area of the roof surrounding the window is colored in a way that provides good color contrast between the sample, as observed through the window, and the roof area surrounding the window for ease of identifying sufficient dosing of the strip.

[0013]The third new feature of the test strip is the inclusion of a notch, or multiple notches, located at the sample application port. A notch is created in both the first insulating substrate and the roof of the strip. These notches are dimensioned and positioned so that they overlay one another in the test strip. These notches reduce a phenomenon called “dose hesitation”. When a sample is added to the sample application port of a notchless strip, the sample can hesitate in its introduction into the capillary test chamber. This “dose hesitation” adds to the testing time. When the test strip includes a notch, dose hesitation is reduced. Further, including the notch in both the first insulating substrate and the roof makes it possible for the test sample to approach the sample application port from a wide variety of angles. The angle of approach for the test sample would be more limited if the notch were only in the roof.

[0014]Finally, the fourth new feature of the test strip is a reagent that includes polyethylene oxide from about 100 kilodaltons to about 900 kilodaltons mean molecular weight at concentrations from about 0.2% (weight:weight) to about 2% (weight:weight), which makes the dried reagent more hydrophilic and sturdier. With the inclusion of polyethylene oxide, the test reagent can more readily withstand mechanical punching during strip assembly and mechanical manipulation by the user of the test strip. Further, the dried reagent, which will include from about 1.75% (weight:weight) to about 17.5% (weight:weight) polyethylene oxide, can easily redissolve, or resuspend, when an aqueous test sample is added to the strip's test chamber.

Problems solved by technology

However, test strips that have been previously made present certain problems for individuals who use them.

For example, test strips are relatively small and a vision impaired diabetic may have great difficulty properly adding a sample of blood to the sample application area of the test strip.

When the test strip is a capillary fill device, that is, when the chemical reaction chamber of the test strip is a capillary space, particular problems can occur with filling the chamber smoothly and sufficiently with the liquid sample to be tested.

Due to the smallness of the capillary space and the composition of materials used to make the test strip, the test sample may hesitate entering the capillary reaction chamber.

Further, insufficient sample may also be drawn into the capillary reaction chamber, thereby resulting in an inaccurate test result.

Processes, such as mechanical punching, used to make these test strips can cause a test reagent that has been dried onto a surface of the testing area to crack or break, thereby causing reagent loss or improper placement of the reagent within the strip.

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