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No calibration analyte sensors and methods

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No calibration analyte sensors and methods


A meter and sensors, for use in combination, where no calibration code has to be entered by the user or is read by the meter. The meter is configured with a predetermined slope and y-intercept built into the meter. If the slope and y-intercept of the sensor are within a predetermined area or grid, or otherwise close to the slope and y-intercept of the meter, the batch of sensors is acceptable for use with that meter for providing accurate analyte concentration results.

Browse recent Abbott Diabetics Care Inc. patents - ,
Inventors: Shridhara Alva Karinka, Yi Wang
USPTO Applicaton #: #20120318670 - Class: 204406 (USPTO) - 12/20/12 - Class 204 
Chemistry: Electrical And Wave Energy > Apparatus >Electrolytic >Analysis And Testing >With Significant Electrical Circuitry Or Nominal Computer Device

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The Patent Description & Claims data below is from USPTO Patent Application 20120318670, No calibration analyte sensors and methods.

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CROSS REFERENCE TO RELATED APPLICATIONS

This Application claims priority to U.S. Provisional Application No. 60/914,590 filed on Apr. 27, 2007, titled “NO CALIBRATION ANALYTE SENSORS AND METHODS,” the disclosure of which is hereby incorporated by reference in its entirety.

BACKGROUND

Biosensors, also referred to as analytical sensors or merely sensors, are commonly used to determine the presence and concentration of a biological analyte in a sample. Such biosensors are used, for example, to monitor blood glucose levels in diabetic patients.

As sensors continue to be used, there continues to be an interest in sensors that are easy to manufacture and easy for a patient to use.

SUMMARY

The present disclosure provides sensors and methods for the detection and quantification of an analyte in a sample. The sensors are configured to provide a clinically accurate analyte level reading, without the user having to enter a calibration code or the like that corresponds to the sensor. The sensors are configured to be used with a meter that has a predetermined calibration code present therein. Embodiments of the sensor are provided, by the manufacturer of the sensors, with a configuration that provides a standardized calibration.

In general, certain embodiments of the present disclosure include sensors for analysis of an analyte in a sample, e.g., a small volume sample, by, for example, coulometry, amperometry and/or potentiometry. The sensors include at least a working electrode and a counter electrode, which may be on the same substrate (e.g., co-planar) or may be on different substrates (e.g., facing). The sensors also include a sample chamber to hold the sample in electrolytic contact with the working electrode. A sensor according to the present disclosure may utilize an electron transfer agent and/or a redox mediator. The sensors may be made with at least one substrate and configured for side-filling, tip-filling, or top-filling. In addition, in some embodiments, the sensor may be part of an integrated sample acquisition and analyte measurement device. An integrated sample acquisition and analyte measurement device may include a sensor and a skin piercing member, so that the device can be used to pierce the skin of a user to cause flow of a fluid sample, such as blood, that may then be collected by the sensor. In at least some embodiments, the fluid sample may be collected without moving the integrated sample acquisition and analyte measurement device.

Various embodiments of methods of making sensors, according to this disclosure, include providing a sample chamber and/or measurement zone having an electrode surface area that, when filled with a sample to be tested, provides a clinically accurate analyte level reading, without the user having to enter a calibration code or the like that corresponds to the sensor, into a meter that is used to read the sensor. The meter is configured with a predetermined slope and y-intercept built into the meter. If the slope and y-intercept (which relate to the calibration code) of the sensor are within a predetermined area or grid, or otherwise close to the slope and y-intercept of the meter, the batch of sensors is acceptable for use with that meter.

In certain embodiments, one particular method of forming a sensor, as described further below, includes forming at least one working electrode on a first substrate and forming at least one counter or counter/reference electrode on a second substrate. A spacer layer is disposed on either the first or second substrates. The spacer layer defines a chamber into which a sample may be drawn and held when the sensor is completed. Chemistry for detecting one or more analytes may be present on the first or second substrate in a region that will be exposed within the sample chamber when the sensor is completed. The first and second substrates may then be brought together and spaced apart by the spacer layer with the sample chamber providing access to the at least one working electrode and the at least one counter or counter/reference electrode. Any or all of the volume of the sample chamber, the volume of the measurement zone, the surface area of the electrode(s) within the sample chamber and/or measurement zone, may be adjusted during the manufacturing process so that the resulting sensor meets certain criteria.

Certain other embodiments include forming at least one working electrode on a first substrate and forming at least one counter or counter/reference electrode on the same, first substrate. One or two additional layers may be added to define a chamber into which a sample may be drawn and held when the sensor is completed. Chemistry may be present in a region that will be exposed within the sample chamber when the sensor is completed. The substrates may then be brought together, forming a sample chamber providing access to the at least one working electrode and the at least one counter or counter/reference electrode. In some embodiments, the volume of the sample chamber, and optionally the volume of the measurement zone, may be adjusted so that the resulting sensor meets certain criteria. Adjusting the volume of the sample chamber may or may not modify the electrode area. Additionally or alternately, in some embodiments, the surface area of the at least one working electrode and/or the at least one counter or counter/reference electrode are adjusted so that the resulting sensor meets certain criteria. Adjusting the electrode area may or may not modify the volume of the sample chamber.

These and various other features which characterize some embodiments according to the present disclosure are pointed out with particularity in the attached claims. For a better understanding of the embodiments, their advantages, and objectives obtained by their use, reference should be made to the drawings and to the accompanying description, in which there is illustrated and described particular embodiments according to the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring now to the drawings, wherein like reference numerals and letters indicate corresponding structure throughout the several views:

FIG. 1 is a schematic perspective view of a first embodiment of a sensor strip in accordance with the present disclosure;

FIG. 2A is an exploded view of the sensor strip shown in FIG. 1, the layers illustrated individually with the electrodes in a first configuration;

FIG. 2B is a top view of the sensor strip shown in FIGS. 1 and 2A;

FIG. 3A is a schematic view of a second embodiment of a sensor strip in accordance with the present disclosure, the layer illustrated individually with the electrodes in a second configuration;

FIG. 3B is a top view of the sensor strip shown in FIG. 3A;

FIG. 4 is a top view of the first substrate of the sensor strip of FIGS. 3A and 3B;

FIG. 5 is a schematic perspective view of another embodiment of a sensor strip in accordance with the present disclosure;

FIG. 6 is a top perspective view of a sensor strip positioned for insertion within an electrical connector device in accordance with the present disclosure;

FIG. 7 is a graphical distribution of results around the calibration position based on standard deviation;

FIG. 8 is a graphical range of slope and intercept with respect to a fixed point that would meet the ISO requirements at a given glucose level; and

FIG. 9 is a graphical range of slope and intercept with respect to a fixed point that would meet the ISO requirements at multiple glucose levels.

FIG. 10 is a schematic block diagram of a meter according to the present disclosure.

DETAILED DESCRIPTION

In some currently available analyte testing systems, a value indicative of the calibration code of a sensor is manually entered into the meter or other equipment, for example, by the user. Based on the calibration code, the meter uses one of several programs or parameters stored within the meter. In other currently available systems, the sensor calibration code is directly read by the meter or other equipment, thus not requiring input or other interaction by the user. These sensors, however, still have a calibration code associated with them, which includes slope and y-intercept values. The slope and y-intercept values are used to determine the analyte concentration based on the measured signal. The calibration code, whether inputted manually or automatically, is needed to standardize the analysis results received from non-standardized sensors. In other words, different sensors vary, e.g., from lot to lot, a sufficient amount that, if no compensation were made, the results would differ from sensor to sensor and the results could be clinically inaccurate.

The sensors of this disclosure are calibration-adjusted to a pre-determined calibration (slope and y-intercept), during the manufacturing process, to avoid the need for the user to input or otherwise set a calibration code for the sensor or perform other calibration procedure(s) before using the sensor. The sensors of this disclosure are also calibration-adjusted to avoid the need for the meter to read a calibration code.

This disclosure also provides methods for making sensors that avoid the need for the user to input or otherwise set a calibration code for the sensor, or perform other calibration procedure(s) before using the sensor. The approach described here does not require any additional steps from the user to perform a test. The manufacturing is simple and does not require special packaging or encoding the strips with calibration information.

In general, the calibration code is a combination of slope and intercept or any other mathematical relationship between a measured signal and the concentration of the analyte in the sample.

In some manufacturing process for sensors, the calibration parameters vary from sensor batch (e.g., batch of 1,000, 5,000, etc. sensors) to sensor batch, due to variations in the composition of the active chemistry and/or variations in any inactive components. The present disclosure provides sensors and methods of making sensors in a manner so that the calibration information does not change from one batch to the other.

Referring to the Drawings in general and FIGS. 1 and 2A in particular, a first embodiment of a sensor strip 10 is schematically illustrated. Sensor strip 10 has a first substrate 12, a second substrate 14, and a spacer 15 positioned therebetween. Sensor strip 10 includes at least one working electrode 22 and at least one counter electrode 24. Sensor strip 10 also includes an optional insertion monitor 30.

Sensor Strips

Referring to FIGS. 1, 2A and 2B in particular, sensor strip 10 has first substrate 12, second substrate 14, and spacer 15 positioned therebetween. Sensor strip 10 includes working electrode 22, counter electrode 24 and insertion monitor 30. Sensor strip 10 is a layered construction, in certain embodiments having a generally rectangular shape, i.e., its length is longer than its width, although other shapes are possible as well. Sensor strip 10′ of FIGS. 3A and 3B also has first substrate 12, second substrate 14, spacer 15, working electrode 22, counter electrode 24 and insertion monitor 30.

The dimensions of a sensor may vary. In certain embodiments, the overall length of sensor strip 10, 10′ may be no less than about 20 mm and no greater than about 50 mm. For example, the length may be between about 30 and 45 mm; e.g., about 30 to 40 mm. It is understood, however that shorter and longer sensor strips 10, 10′ could be made. In certain embodiments, the overall width of sensor strip 10, 10′ may be no less than about 3 mm and no greater than about 15 mm. For example, the width may be between about 4 and 10 mm, about 5 to 8 mm, or about 5 to 6 mm. In one particular example, sensor strip 10, 10′ has a length of about 32 mm and a width of about 6 mm. In another particular example, sensor strip 10, 10′ has a length of about 40 mm and a width of about 5 mm. In yet another particular example, sensor strip 10, 10′ has a length of about 34 mm and a width of about 5 mm.

Substrates

As provided above, sensor strip 10, 10′ has first and second substrates 12, 14, non-conducting, inert substrates which form the overall shape and size of sensor strip 10, 10′. Substrates 12, 14 may be substantially rigid or substantially flexible; in some embodiments, one substrate may be rigid and the other substrate may be flexible. In certain embodiments, substrates 12, 14 are flexible or deformable. Examples of suitable materials for substrates 12, 14 include, but are not limited to, polyester, polyethylene, polycarbonate, polypropylene, nylon, and other “plastics” or polymers. In certain embodiments the substrate material is “Melinex” polyester. Other non-conducting materials may also be used.

Spacer Layer

As indicated above, positioned between substrate 12 and substrate 14 can be spacer 15 to separate first substrate 12 from second substrate 14. Spacer 15 is an inert non-conducting substrate, typically at least as flexible and deformable (or as rigid) as substrates 12, 14. In certain embodiments, spacer 15 is an adhesive layer or double-sided adhesive tape or film. Any adhesive selected for spacer 15 should be selected to not diffuse or release material which may interfere with accurate analyte measurement. Spacer 15 may be generally the same size as substrates 12, 14 or may occupy less than the width and/or length of substrates 12, 14. In certain embodiments, the thickness of spacer 15 may be at least about 0.01 mm (10 μm) and no greater than about 1 mm or about 0.5 mm. For example, the thickness may be between about 0.02 mm (20 μm) and about 0.2 mm (200 μm). In one certain embodiment, the thickness is about 0.05 mm (50 μm), and about 0.1 mm (100μm) in another embodiment.

Sample Chamber

The sensor includes a sample chamber for receiving a volume of sample to be analyzed; in the embodiment illustrated, particularly in FIG. 1, sensor strip 10, 10′ includes sample chamber 20 having an inlet 21 for access to sample chamber 20. In the embodiments illustrated, sensor strips 10, 10′ are side-fill sensor strips, having inlet 21 present on a side edge of strips 10, 10′. Tip-fill sensors can also be configured in accordance with the present disclosure. Referring to FIG. 5, a tip-filled sensor strip 10″ is illustrated. Similar to sensor strips 10, 10′, sensor strip 10″ has substrates 12, 14 with spacer 15 therebetween and an insertion indicator 30. Sensor strip 10″, however, has a sample chamber 20′ that extends from an inlet 21′ positioned at a tip of sensor strip″. Sensor strip 10″ includes a vent hole 29 in substrate 14 to facilitate drawing of sample into sample chamber 20′ via inlet 21′. It is noted that hole 29, in some embodiments, could be used as a sample inlet.

Sample chamber 20, 20′ is configured so that when a sample is provided in chamber 20, 20′, the sample is in electrolytic contact with both the working electrode and the counter electrode, which allows electrical current to flow between the electrodes to effect the electrolysis (electrooxidation or electroreduction) of the analyte.

Sample chamber 20, 20′ is defined by substrate 12, substrate 14 and spacer 15; in many embodiments, sample chamber 20, 20′ exists between substrate 12 and substrate 14 where spacer 15 is not present. Typically, a portion of spacer 15 is removed to provide an area between substrates 12, 14 without spacer 15; this volume of removed spacer is sample chamber 20, 20′. For embodiments that include spacer 15 between substrates 12, 14, the thickness of sample chamber 20, 20′ is generally the thickness of spacer 15. Other methods for forming sample chamber 20, 20′ could additionally or alternately be used.

Sample chamber 20, 20′ has a volume sufficient to receive a sample of biological fluid therein. In some embodiments, such as when sensor strip 10, 10′, 10″ is a small volume sensor, sample chamber 20, 20′ has a volume that is preferably no more than about 1 μL, for example no more than about 0.5 μL, and also for example, no more than about 0.25 μL. A volume of no more than about 0.1 μL is also suitable for sample chamber 20, as are volumes of no more than about 0.05 μL and about 0.03 μL.

A measurement zone is contained within sample chamber 20, 20′ and is the region of the sample chamber that contains only that portion of the sample that is interrogated during the analyte assay. In some designs, the measurement zone has a volume that is approximately equal to the volume of sample chamber 20, 20′. In some embodiments the measurement zone includes 80% of the sample chamber, 90% in other embodiments, and about 100% in yet other embodiments.

As provided above, the thickness of sample chamber 20, 20′ corresponds typically to the thickness of spacer 15. Particularly for facing electrode configurations, this thickness is small to promote rapid electrolysis of the analyte, as more of the sample will be in contact with the electrode surface for a given sample volume. In addition, a thin sample chamber 20, 20′ helps to reduce errors from diffusion of analyte into the measurement zone from other portions of the sample chamber during the analyte assay, because diffusion time is long relative to the measurement time, which may be about 5 seconds or less.

Electrodes

As provided above, the sensor includes a working electrode and at least one counter electrode. The counter electrode may be a counter/reference electrode. If multiple counter electrodes are present, one of the counter electrodes will be a counter electrode and one or more may be reference electrodes. Referring to FIGS. 2A and 2B and FIGS. 3A, 3B and 4, two examples of suitable electrode configurations are illustrated.

Working Electrode

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stats Patent Info
Application #
US 20120318670 A1
Publish Date
12/20/2012
Document #
13550166
File Date
07/16/2012
USPTO Class
204406
Other USPTO Classes
International Class
01N27/26
Drawings
7



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