Patent Application
20080011616
While the invention is susceptible to various modifications and alternative forms, specific embodiments are shown by way of example in the drawings and are described in detail herein. It should be understood, however, that the invention is not intended to be limited to the particular forms disclosed. Rather, the invention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the invention.
The present invention is directed to an electrochemical test sensor that is adapted to be placed into a meter or an instrument and assist in determining an analyte concentration in a body fluid sample. The body fluid sample may be collected with a lancing device. Examples of the types of analytes that may be collected include glucose, lipid profiles (e.g., cholesterol, triglycerides, LDL and HDL), microalbumin, hemoglobin A1C, fructose, lactate, or bilirubin. It is contemplated that other analyte concentrations may also be determined. The analytes may be in, for example, a whole blood sample, a blood serum sample, a blood plasma sample, other body fluids like ISF (interstitial fluid) and urine, and non-body fluids. As used within this application, the term “concentration” refers to an analyte concentration, analyte level, activity (e.g., enzymes and electrolytes), titers (e.g., antibodies), or any other measure concentration used to measure the desired analyte.
Referring initially to
The function of the reagent layer 44 is to convert an analyte (e.g., glucose) in the fluid test sample, stoichiometrically into a chemical species that is electrochemically measurable, in terms of electrical current it produces, by the components of the working electrode 39 and counter electrode 40. The reagent layer 44 typically includes an enzyme and an electron acceptor. The enzyme reacts with the analyte to produce mobile electrons on the working and counter electrodes 39, 40. For example, the reagent layer 44 may include glucose oxidase or glucose dehydrogenase if the analyte to be determined is glucose. The enzyme in the reagent layer 44 may be combined with a hydrophilic polymer such as poly(ethylene oxide) or other polymers such as polyethylene oxide (PEO), hydroxyethyl cellulose (HEC), carboxymethylcellulose (CMC) and polyvinyl acetate (PVA). The electron acceptor (e.g., ferricyanide salt) carries the mobile electrons to the surface of the working electrode 39.
The working electrode 39 and the counter electrode 40 assist in electrochemically determining the analyte concentration. In one embodiment, the working electrode 39 and the counter electrode 40 comprise a mixture of amorphous and graphite forms of carbon that is chosen to be electrochemically active and provide a low electrical resistance path between the electrodes and the meter-contact area 38. In another embodiment, the working electrode 39 and the counter electrode 40 comprises a mixture of carbon and silver. It is contemplated that the working electrode 39 and the counter electrode 40 may be made of other materials that assist in providing an electrical path to the meter or instrument with which they are in operative connection. The reagent layer 44, as shown in
A three-dimensional lid 46 forms a concave space 48 over the base 36 and the components located thereon eventually form a capillary space or channel. The lid 46 may be formed by embossing a flat sheet of deformable material and then joining the lid 46 to the base 36 in a sealing operation. The material forming the lid 46 may be a deformable polymeric sheet material (e.g. polycarbonate or an embossable grade of polyethylene terphthalate), or a glycol modified polyethylene terephthatalte. It is contemplated that other materials may be used in forming the lid 46.
The material forming the lid 46 may be punctured to provide at least one air vent 50. The air vent 50 is desirable because it assists in preventing or inhibiting air-lock. By preventing or inhibiting air-lock, a fluid sample is better able to enter the capillary channel 48 in a timely manner.
Suitable materials for the insulating base 36 of
The lid 46 and the base 36 may be sealed together by a variety of methods. For example, the lid 46 and the base 36 may be sealed together by sonic welding in which the base 36 and the lid 46 are first aligned and then pressed together between a vibratory heat sealing member or horn and a stationary jaw. In this method, the horn is shaped such that contact is made only with the flat, non-embossed regions of the lid 46. Ultrasonic energy from a crystal or other transducer is used to excite vibrations in the metal horn. This mechanical energy is dissipated as heat in the polymeric joint allowing the bonding of the thermoplastic materials. In another method, the lid 46 and the base 36 are joined by using an adhesive material on the underside of the lid 46. It is contemplated that other methods may be used to attach the lid and the base.
In electrochemical test sensors, it is desirable to have a defined area on the electrode pattern to ensure an accurate meter reading. A defined area is important because the measured current is dependent both on the concentration of the analyte and the area of the working electrode that is exposed to the analyte containing the test sample.
When manufacturing the test sensor 34, the concave space 48 formed by the lid 46 may vary in location over the base 36. This is caused by manufacturing tolerances in forming the lid 46, the base 36, the concave space 48, and the placement of the lid 46 to the base 36. Thus, different areas of the working electrode 39 may be exposed to the fluid test sample via the concave space 48, which may affect the accuracy of the meter reading. Furthermore, if the lid 46 and the base 36 are joined with an adhesive on the underside of the lid 46, there may be some adhesive material “squeeze-out” such that the adhesive material extends past the flat, non-embossed regions of the lid 46 and onto a portion of the working electrode 39 that is exposed to the analyte. The adhesive material “squeeze-out” may affect the reading of the electrochemical test sensor 34. However, the effect of these manufacturing processes is minimized in the present invention due to the shape of, for example, the working electrode 39. In this example, the working electrode may produce consistent readings without using a dielectric layer.
Referring to
Referring specifically now to
Although the entire main portion 39a of the working electrode 39 desirably remains in the concave space 48 despite the potential for the concave space 48 to vary in location, the area exposed to contact by the fluid test sample of the secondary portions 39b,c may vary due to the mating of the lid 46 and the base 36 (see, for example, the concave space 48 of
In
The area of the main portion 39a of the working electrode is 0.00115 in2, which is the product of its width w2 (0.023 inches) multiplied by its height h2 (0.05 inches). In the illustrated embodiment, the main portion 39a of the working electrode 39 is directly in the center of the width w1 of the concave opening 48. Since the width w1 is 0.043 inches and the main portion 39a is 0.023 inches in width w2, the portion of each secondary portion 39b,c exposed by the concave space 48 is about 0.01 inches [(0.043−0.023)/2] (identified by arrow w4). Thus, the area of each secondary portion 39b,c exposed by the concave space 48 is the product of its width w4 (0.01 inches) multiplied by its height h3 (0.005 inches), resulting in a contact area of 0.00005 in2 for each secondary portion 39b,c. The area of the main portion 39a (0.00115 in2) is about 12 times larger than the total area of the secondary portions 39b,c (0.0001 in2) exposed to the fluid test sample. However, other proportions in area may also work in accordance with the present invention. In some embodiments, the total area of the main portion 39a of the working electrode 39 may be about 5 times the size of the area of the secondary portions 39b,c of the working electrode 39. Preferably, the main portion 39a of the working electrode 39 is at least 10 or at least 20 times the size of the area of the secondary portions 39b,c of the working electrode 39.
Referring now to
Other variations in the location of the concave space (e.g., 48, 58) over the working electrode 39 will also not significantly affect the meter reading. As discussed above, the main portion 39a of the working electrode 39 desirably remains entirely within the concave space, despite variations in its location. Since only a small area of the secondary portions 39b,c is affected by a shift in the location of the concave space, the overall electrical current produced by the entire contacted area of the working electrode 39 will not be significantly affected. As such, the shape of the working electrode 39 is adapted to produce consistently reproducible meter readings with other locations of the concave space (not illustrated). Furthermore, since only a small area of the secondary portions 39b,c would be affected by an adhesive “squeeze-out,” as mentioned above, the overall electrical current produced by the entire contacted area of the working electrode 39 would not be significantly affected.
As can be seen in
As shown in
Other shapes of the main portion of the working electrode may also be used.
While alternative embodiments of the working electrode have been provided above, the working electrode may also take other, non-illustrated, embodiments. Whatever its specific shape, the working electrode should include a voluminous main portion filling a large portion of the capillary channel and at least one smaller secondary portion.
The design of the working electrode of the present invention is not limited to use with a three-dimensional embossed lid forming a concave space, such as the lid 46. Other ways of forming a concave space over a working electrode in an electrochemical test sensor may also be used in accordance with the present invention. For example,
While the invention is susceptible to various modifications and alternative forms, specific embodiments and methods thereof have been shown by way of example in the drawings and are described in detail herein. It should be understood, however, that it is not intended to limit the invention to the particular forms or methods disclosed, but, to the contrary, the intention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the invention.
An electrochemical test sensor for detecting the concentration of analyte in a fluid test sample, the electrochemical test sensor comprising:
a base that provides a flow path for the fluid test sample having on its surface a counter electrode and a working electrode in electrical communication with a detector of electrical current;
a reagent layer directly located on the surface of the working electrode, the reagent layer including an enzyme that is adapted to react with the analyte; and
a lid adapted to mate with the base and to assist in forming a capillary space with an opening for the introduction of fluid test sample thereto, the capillary space being formed with a three-dimensional portion of the lid.
The test sensor of Alternative Embodiment A wherein the reagent layer is further located on the surface of the counter electrode.
The test sensor of Alternative Embodiment A wherein the area of the working electrode adapted to interact with the analyte of the fluid test sample includes a main portion and at least one secondary portion extending therefrom.
The test sensor of Alternative Embodiment C wherein the main portion of the working electrode has a first width in a first direction and the at least one secondary portion has a second width in the first direction, the first width being at least 2 times greater than the second width.
The test sensor of Alternative Embodiment D wherein the main portion of the working electrode has a first height in a second direction and the at least one secondary portion has a second height in the second direction, the second direction being generally perpendicular to the first direction, the first height being from about 5 to about 15 times greater than the second height.
The test sensor of Alternative Embodiment C wherein the at least one secondary portion of the working electrode is generally polygonal.
The test sensor of Alternative Embodiment F wherein the main portion of the working electrode is generally polygonal.
The test sensor of Alternative Embodiment F wherein the main portion of the working electrode is generally non-polygonal.
The test sensor of Alternative Embodiment A wherein the capillary space is less than about 0.75 μL.
The test sensor of Alternative Embodiment A wherein the capillary space is less than about 0.6 μL.
An electrochemical test sensor for detecting the concentration of analyte in a fluid test sample, the electrochemical test sensor comprising:
a base that provides a flow path for the fluid test sample having on its surface a counter electrode and a working electrode in electrical communication with a detector of electrical current, the working electrode includes a main portion and at least two secondary portions extending therefrom;
a reagent layer directly located on the surface of the working electrode, the reagent layer including an enzyme that is adapted to react with the analyte; and
a lid adapted to mate with the base and to assist in forming a capillary space with an opening for the introduction of fluid test sample thereto.
The test sensor of Alternative Embodiment K wherein one of the secondary portions of the working electrode is in electrical communication with the detector.
The test sensor of Alternative Embodiment K wherein the main portion of the working electrode is disposed between the at least two secondary portions of the working electrode, the at least two secondary portions of the working electrode being generally opposite from each other.
The test sensor of Alternative Embodiment L wherein the area of the main portion of the working electrode is substantially larger than the area of the secondary portions of the working electrode.
An electrochemical test sensor for detecting the concentration of analyte in a fluid test sample, the electrochemical test sensor comprising:
a base that provides a flow path for the fluid test sample having on its surface a counter electrode and a working electrode in electrical communication with a detector of electrical current;
a reagent layer directly located on the surface of the working electrode, the reagent layer including an enzyme that is adapted to react with the analyte, the working electrode including a main portion having a first width in a first direction and further including at least one secondary portion extending from the main portion having a second width in the first direction, the first width being at least about 2 times greater than the second width; and
a lid adapted to mate with the base and to assist in forming a capillary space with an opening for the introduction of fluid test sample thereto.
The test sensor of Alternative Embodiment O further including a spacer that is adapted to assist in forming the capillary opening, the spacer being located between the base and the lid.
The test sensor of Alternative Embodiment O wherein the main portion of the working electrode has a first height in a second direction and the at least one secondary portion has a second height in the second direction, the second direction being generally perpendicular to the first direction, the first height being from about 5 to about 15 times greater than the second height.
The test sensor of Alternative Embodiment O wherein the at least one secondary portion of the working electrode is generally polygonal.
The test sensor of Alternative Embodiment R wherein the main portion of the working electrode is generally polygonal.
The test sensor of Alternative Embodiment R wherein the main portion of the working electrode is generally non-polygonal.
The test sensor of Alternative Embodiment S wherein the capillary space is less than about 0.75 μL.
The test sensor of Alternative Embodiment S wherein the capillary space is less than about 0.6 μL.
A method for determining the concentration of an analyte in a fluid test sample with a test sensor, the method comprising the acts of:
providing a base that provides a flow path for the fluid test sample having on its surface a counter electrode and a working electrode in electrical communication with a detector of electrical current, the working electrode includes a main portion and at least two secondary portions extending therefrom, a reagent layer being directly located on the surface of the working electrode, the reagent layer including an enzyme that is adapted to react with the analyte, a lid being adapted to mate with the base and to assist in forming a capillary space with an opening for the introduction of fluid test sample thereto;
contacting the reagent layer with the fluid sample via the capillary space;
generating an electrical signal in the test sensor in response to the presence of the analyte; and
determining the concentration of the analyte from the electrical signal.
A method for determining the concentration of an analyte in a fluid sample with a test sensor, the method comprising the acts of:
providing an electrochemical test sensor comprising a base that provides a flow path for the fluid test sample having on its surface a counter electrode and a working electrode in electrical communication with a detector of electrical current, a reagent layer being directly located on the surface of the working electrode, the reagent layer including an enzyme that is adapted to react with the analyte, and a lid being adapted to mate with the base and to assist in forming a capillary space with an opening for the introduction of fluid test sample thereto, the capillary space being formed with a three-dimensional portion of the lid;
contacting the reagent layer with the fluid sample via the capillary space;
generating an electrical signal in the test sensor in response to the presence of the analyte; and
determining the concentration of the analyte from the electrical signal.
The method of Alternative Process X wherein the working electrode includes a main portion and at least two secondary portions adapted to interact with the liquid sample.
The method of Alternative Process Y wherein the area of the main portion of the working electrode is at least 10 times the area of the at least two secondary portions of the working electrode adapted to interact with the fluid sample.
The method of Alternative Process X wherein the analyte is glucose.
The method of Alternative Process X wherein the capillary space is less than about 0.75 μL.
This application claims priority to Application No. 60/819,961 filed on Jul. 11, 2006, which is incorporated by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 60819961 | Jul 2006 | US |
