Surgery – Diagnostic testing – Measuring or detecting nonradioactive constituent of body...
Reexamination Certificate
2000-07-10
2002-11-19
Shaver, Kevin (Department: 3736)
Surgery
Diagnostic testing
Measuring or detecting nonradioactive constituent of body...
C600S347000, C600S309000, C600S365000
Reexamination Certificate
active
06484046
ABSTRACT:
FIELD OF THE INVENTION
The present invention is, in general, directed to an analyte sensor. More particularly, the present invention relates to an electrochemical sensor for determining a level of an analyte, such as glucose, lactate, or oxygen, in vivo and/or in vitro.
BACKGROUND OF THE INVENTION
The monitoring of the level of glucose or other analytes, such as lactate or oxygen, in certain individuals is vitally important to their health. High or low levels of glucose or other analytes may have detrimental effects. The monitoring of glucose is particularly important to individuals with diabetes, as they must determine when insulin is needed to reduce glucose levels in their bodies or when additional glucose is needed to raise the level of glucose in their bodies.
A conventional technique used by many diabetics for personally monitoring their blood glucose level includes the periodic drawing of blood, the application of that blood to a test strip, and the determination of the blood glucose level using calorimetric, electrochemical, or photometric detection. This technique does not permit continuous or automatic monitoring of glucose levels in the body, but typically must be performed manually on a periodic basis. Unfortunately, the consistency with which the level of glucose is checked varies widely among individuals. Many diabetics find the periodic testing inconvenient and they sometimes forget to test their glucose level or do not have time for a proper test. In addition, some individuals may wish to avoid the pain associated with the test. These situations may result in hyperglycemic or hypoglycemic episodes. An in vivo glucose sensor that continuously or automatically monitors the individual's glucose level would enable individuals to more easily monitor their glucose, or other analyte, levels.
A variety of devices have been developed for continuous or automatic monitoring of analytes, such as glucose, in the blood stream or interstitial fluid. Many of these devices use electrochemical sensors which are directly implanted into a blood vessel or in the subcutaneous tissue of a patient. However, these devices are often difficult to reproducibly and inexpensively manufacture in large numbers. In addition, these devices are typically large, bulky, and/or inflexible, and many can not be used effectively outside of a controlled medical facility, such as a hospital or a doctor's office, unless the patient is restricted in his activities.
The patient's comfort and the range of activities that can be performed while the sensor is implanted are important considerations in designing extended-use sensors for continuous or automatic in vivo monitoring of the level of an analyte, such as glucose. There is a need for a small, comfortable device which can continuously monitor the level of an analyte, such as glucose, while still permitting the patient to engage in normal activities. Continuous and/or automatic monitoring of the analyte can provide a warning to the patient when the level of the analyte is at or near a threshold level. For example, if glucose is the analyte, then the monitoring device might be configured to warn the patient of current or impending hyperglycemia or hypoglycemia. The patient can then take appropriate actions.
In addition to in vivo monitoring of analyte levels, it is often important to determine the level of an analyte in a sample taken from a subject. For many individuals and for many analytes, continuous monitoring of analyte level is not necessary, convenient, and/or desirable. In vitro measurements are often useful in making periodic determinations of analyte level when an in vivo sensor is not being used. Such measurements may also be useful for calibrating an in vivo sensor. In these cases, it may be desirable to use small volume samples due to the difficulty of obtaining such samples, the discomfort of the patient when the sample is obtained, and/or other reasons. However, most conventional sensors are designed to test for analyte levels in samples larger than 3 microliters. It is desirable to have sensors that could be used for the in vitro monitoring of samples that may be as small as a microliter, or even 25 nanoliters or less. The use of such small samples reduces the inconvenience and pain associated with obtaining a sample, for example, by lancing a portion of the body to obtain a blood sample.
SUMMARY OF THE INVENTION
Generally, the present invention relates to an analyte sensor which can be used for the in vivo and/or in vitro determination of a level of an analyte in a fluid. Some embodiments of the invention are particularly useful for the continuous or automatic monitoring of a level of an analyte, such as glucose or lactate, in a patient. One embodiment of the invention is an electrochemical sensor. The electrochemical sensor includes a substrate, a recessed channel formed in a surface of the substrate, and a conductive material disposed in the recessed channel. The conductive material forms a working electrode.
Another embodiment of the invention is an electrochemical sensor that includes a substrate and a plurality of recessed channels formed in at least one surface of the substrate. Conductive material is disposed in each of the recessed channels. The conductive material in at least one of the recessed channels forms a working electrode.
A further embodiment of the invention is an analyte responsive electrochemical sensor that includes a working electrode and a mass transport limiting membrane. The mass transport limiting membrane preferably maintains a rate of permeation of the analyte through the mass transport limiting membrane with a variation of less than 3% per ° C. at temperatures ranging from 30° C. to 40° C.
Yet another embodiment of the invention is a method of determining a level of an analyte in a fluid. The fluid is contacted by an electrochemical sensor that includes a substrate, a recessed channel in the substrate, and conductive material in the recessed channel forming a working electrode. An electrical signal is generated by the sensor in response to the presence of the analyte. The level of the analyte may be determined from the electrical signal.
A further embodiment of the invention is a temperature sensor. The temperature sensor includes a substrate, a recessed channel formed in the substrate, and a temperature probe disposed in the recessed channel. The temperature probe includes two probe leads that are disposed in spaced-apart portions of the recessed channel and a temperature-dependent element that is disposed in the recessed channel and is in contact with the two probe leads. The temperature-dependent element is formed using a material having a temperature-dependent characteristic that alters a signal from the temperature probe in response to a change in temperature.
One embodiment of the invention is a method of determining a level of an analyte in a fluid. The fluid is placed in contact with an electrochemical sensor. The electrochemical sensor has a substrate, a recessed channel formed in a surface of the substrate, conductive material disposed in the recessed channel to form a working electrode, and a catalyst proximally disposed to the working electrode. A level of a second compound in the fluid is changed by a reaction of the analyte catalyzed by the catalyst. A signal is generated in response to the level of the second electrode. The level of the analyte is determined from the signal.
Another embodiment of the invention is an electrochemical sensor having a substrate and a working electrode disposed on the substrate. The working electrode preferably includes a carbon material and has a width along at least a portion of the working electrode of 150 &mgr;m or less.
Another embodiment of the invention is an electrochemical sensor for determining a level of an analyte in a fluid. The electrochemical sensor includes a substrate, a recessed channel formed in a surface of the substrate, and conductive material disposed in the recessed channel to form a working electrode. A catalyst is positione
Aria Behrad
Gal Yoram
Heller Adam
Heller Ephraim
Plante Phillip John
Natnithithadha Navin
Shaver Kevin
TheraSense Inc.
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