Implantable Glucose Monitoring System for Diabetics

Implantable Glucose Sensor

Background - Diabetes mellitus is a serious disease affecting up to 8% of the world's population in many (particularly advanced) societies. It is becoming increasingly prevalent worldwide as populations age and dietary habits change. Depending upon its severity, it is controlled by either daily insulin injections, drugs, or in mild cases, diet. There are two forms of the disease, Type 1 (early onset) and Type 2 (mature onset). Type 1 patients, in particular, suffer a substantial reduction in average life expectancy; this is due to long term deleterious physiological effects, especially on the circulatory system and to sudden death due to lack of control of blood glucose levels. In the United Kingdom, for example, it is the fourth leading cause of death.

Benefits of continuous glucose monitoring - People with advanced conditions of diabetes, monitoring levels of glucose in their blood is important and is usually achieved by invasive methods (finger pricking), which represents a multi-billion dollar worldwide business, mainly for disposable enzyme based strips. Having obtained a blood sample, it is analyzed in a suitable meter device. Based on the result the patient should adjust their insulin dosage, food intake, and physical activity to keep glucose levels as close to "normal" as possible.

Clinical studies have shown that tight glucose control significantly improves long-term clinical outcomes. The current standard of care recommends that this procedure be repeated a minimum of four times per day. Because of the unpleasant, cumbersome nature of this test regimen, patient compliance is invariably poor.

Implantable Glucose Sensor

Too much glucose (hyperglycemia) indicates that more insulin is required, and too little glucose (hypoglycemia) requires immediate action to raise the levels. Hyperglycemia causes most of the long-term consequences of diabetes, including blindness, nerve degeneration, heart and kidney failure. However, in the short term the more immediate danger is from hypoglycemia (sometimes called insulin shock), which can occur at any time of the day or night and can cause the patient to lose consciousness.

For practical reasons, night time blood glucose variations are often neglected, but nocturnal hypoglycemia can be a particular worry for parents of young diabetics. The best way to avoid such frightful consequences is to frequently monitor the blood glucose levels. If a reliable implantable glucose sensor was used as a hypoglycemia alarm that alerts patients when their glucose levels drops below a threshold value, would reduce the possibility of diabetics suffering from these adverse, harmful effects.

New concept not involving or relying on the use of enzymes. Based on combination of existing technologies in a biocompatible format, totally Implantable and with long term functionality.

The need for an implantable glucose sensor - Without doubt, there is a clear medical need for a reliable, inexpensive continuous blood glucose monitoring device. A variety of clinical studies have indicated that the more blood glucose concentrations are carefully controlled within normal limits, the less likely the patient will suffer serious secondary consequences of the disease. In order to achieve such control, it's necessary to monitor blood glucose concentrations frequently to establish the appropriate insulin or drug doses and dietary regimes. Typically patients with Type1 diabetes have to monitor up to five times per day or more. A radical solution that might rule out the need for frequent glucose testing and insulin administration has been a subject of much clinical research over many years. Two very different types of implantable glucose sensors are being developed a. Percutaneous (through the skin) and b. in vivo - (beneath the skin). The main technique falls into two categories: - a) attempting to achieve measurement transcutaneously and non-invasively or, b) adaptation of biosensor technology for in vivo measurement.

A variety of routes to the first approach have been taken with some success but have not yet lead to a reliable system that could be used for long-term automatic measurement. Nevertheless, products for intensive care applications or clinical measurement have been developed. For example, glucose sensors have successfully been incorporated into needle devices projecting through the skin and some with good short-term performance. Indeed, such devices have been recently commercialized and have been approved by the FDA for clinical applications. However, a fundamental disadvantage with needle devices is it is unlikely to be developed for long-term implantation because of the problem of instability of the enzyme component and their liability to fouling as a result of the body's response to the inserted needle. Nevertheless, some researchers continue to pursue this line of development.