Drug – bio-affecting and body treating compositions – In vivo diagnosis or in vivo testing
Reexamination Certificate
1999-07-09
2002-11-26
Hartley, Michael G. (Department: 1619)
Drug, bio-affecting and body treating compositions
In vivo diagnosis or in vivo testing
C424S009600, C424S009800
Reexamination Certificate
active
06485703
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to the fields of chemistry, biology, biochemistry, medical devices and chemical detection devices. More particularly, it concerns polymeric compositions, methods and devices for the detection of one or more selected analyte(s), preferably detection of one or more analyte(s) in vivo. The present invention also concerns polymeric constructs for analyte detection and concentration measurement using visualization or production of electrochemical signals from a construct after implantation in vivo. In particular, the invention concerns detection or measurement of blood glucose levels in vivo for the management of diabetes. Additionally, devices are provided to detect and measure the optical or electrochemical changes in polymeric constructs.
2. Description of Related Art
Diagnosis of various disease and injury conditions are often made on the basis of the detection and measurement of the concentration of one or more body chemicals or analytes. Currently, the levels of numerous selected body chemicals or analytes are measured manually and invasively by withdrawing a sample of blood. For most analytes the sample is usually sent to a centrally located lab where it is typically analyzed with large and expensive machines using wet chemistry, immunoassays, and/or enzyme electrode based biosensing. This mode of operation is expensive and time consuming, and therefore represents a significant hazard to critically ill patients in operating rooms, intensive care units and trauma/critical care units. In particular, for trauma/critical care cases it is known that survival rates decrease dramatically if treatment is delayed for more than one hour. For instance, the measurement of arterial blood gases is a primary indicator of respiratory function, and lactate values are used as an indicator of shock. Therefore, the frequent assessment of these and other analytes is essential to clinical diagnosis and management.
Exemplary of diseases that require frequent monitoring of analytes is diabetes mellitus. Diabetes mellitus is a chronic disease that, if unregulated, can give rise to large fluctuations in blood glucose levels. This disease currently afflicts over 100 million people worldwide and nearly 14 million in the United States (National Institute of Diabetes and Kidney Diseases, 1994). In the U.S. this disorder, along with its associated complications, is ranked as the seventh leading cause of death (Cotran et al., 1989). In order to maintain normal glucose levels, blood glucose must be monitored frequently throughout the day. Self-monitoring of blood glucose is recommended for diabetic patients as the current standard of care and, since the announcement of the Diabetes Control and Complications Trial results (National Institute of Diabetes & Digestive & Kidney Diseases, 1993), there is now no question that intensive management of blood sugars is an effective means to prevent or at least slow the progression of diabetic complications such as kidney failure, heart disease, gangrene, and blindness (National Institute of Diabetes & Digestive & Kidney Diseases, 1993; Wysocki, 1989; Speicher, 1991).
The goal of diabetes therapy is to approximate the 24-hour blood glucose profile of a normal individual. Without regulation, hypoglycemia, a condition in which the blood glucose level falls well below normal, can result, which can cause the patient to slip into a coma and eventual death. Alternatively, a condition known as hyperglycemia can develop, in which blood glucose levels can rise considerably above normal levels. If left untreated, these abnormally high blood glucose levels may result in long-term complications such as an increased risk of coronary artery disease, hypertension, retinopathy, neuropathy, and nephropathy (National Institute of Diabetes and Kidney Diseases, 1994; Cotran et al., 1989; National Institute of Diabetes & Digestive & Kidney Diseases, 1993; Hanssen, 1986).
Proper treatment includes maintaining blood glucose levels near normal levels. This can only be achieved with frequent blood glucose monitoring so that appropriate actions can be taken, such as insulin injections, proper diet, or exercise. Unfortunately, the currently preferred method of sensing is an invasive technique, requiring a finger stick to draw blood each time a reading is needed. This approach is both time-consuming and painful. Therefore, there is a lack of compliance among the diabetic population for even monitoring their levels once per day, not to mention the recommended five or more times daily (National Institute of Diabetes & Digestive & Kidney Diseases, 1993).
One potential method of achieving tighter metabolic control in diabetic patients is a closed-loop insulin delivery system, incorporating a microprocessor-controlled insulin pump and a glucose sensor. Various amperometric devices have been fabricated based upon the electrochemical oxidation of H
2
O
2
generated during a reaction between glucose and oxygen catalyzed by glucose oxidase (Tatsuma et al., 1994). The focus of amperometric biosensors appears to have shifted towards the incorporation of charge mediators as electron “shuttles” between the redox center of the enzyme and the electrode surface (Hale et al., 1991; Pishko et al., 1991). These H
2
O
2
and mediator based biosensors have taken on many forms, including covalent immobilization directly to the electrode surface, retention by a membrane, or entrapment in a polymer hydrogel (Henning, T. and Cunningham, D., 1998).
Glucose sensors, which use an enzyme (glucose oxidase) to achieve specificity, are currently not stable or sensitive enough to meet the demands of a closed-loop delivery system. As a result, the application of glucose biosensors has been primarily limited to home glucose test meter and blood-gas instruments containing sensors for glucose (Rouhi, 1997). There are a number of reasons for this lack of commercial progress, both technical and economic. Technically, many proposed biosensors for glucose simply do not have the accuracy and stability (operational or storage) to meet the desired need. Inaccuracy and imprecision in sensor performance are frequently due to imprecision in sensor manufacturing, e.g. immobilized biomolecules cannot be deposited on transducer surfaces at the same density and with the same mass transfer limitations. Instability is often a problem inherent in the biomolecule, the result of poor immobilization methods resulting in leaching, or inactivation of the biomolecule by species present in the sensing environment (Pishko, M. V., 1995).
Glucose detection devices have been reported that quantify glucose concentration in blood and body fluids. One such device uses fluorescence resonance energy transfer (FRET) between a labelled ligand and a labelled carbohydrate-containing receptor (U.S. Pat. No. 5,342,789). The binding of glucose to the receptor prevents energy transfer from the labelled receptor to the labelled ligand, and thus prevents the quenching of the flourescence of the labelled receptor.
Noninvasive methods to quantify blood chemicals, particularly glucose, have been attempted using various optical approaches. Four primary approaches being investigated, including near-infrared (NIR) absorption spectroscopy (Small et al., 1993; Marbach et al., 1993; Robinson et al., 1992; McShane et al., 1997), NIR scattering (Kohl and Cope, 1994; Maier et al., 1994), polarimetry (March et al., 1982; Gough, 1982; Cameron and Coté, 1997; King et al., 1994; Coté et al., 1992), and Raman spectroscopy (Goetz, Jr. et al., 1995; Berger et al., 1997).
Each of these approaches suffer primarily from a lack of specificity. The NIR scatter approach is confounded by changes in indices of refraction, since tissue scattering is also caused by a variety of substances and organelles which all have different refractive indices. The Raman approach is non-specific, lacks good sensitivity, requires high powers, and suffers from large background autofluorescence of the tissue in vivo (Coté, G.
Anderson Richard Rox
Cote Gerard L.
Pishko Michael V.
Russell Ryan
Sirkar Kaushik
Hartley Michael G.
Howrey Simon Arnold & White , LLP
The Texas A&M University System
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