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Electrochemical Glucometers

Electrochemical Glucometers. Diabetes . Diabetes affects 17 million Americans and 171 million people worldwide. Two Major Types Type I: Pancreas produces very little or no insulin; affects younger patients

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Electrochemical Glucometers

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  1. Electrochemical Glucometers

  2. Diabetes • Diabetes affects 17 million Americans and 171 million people worldwide. • Two Major Types • Type I: Pancreas produces very little or no insulin; affects younger patients • Type II: Pancreas does not produce enough insulin or does not use produced insulin effectively (insulin resistant); affect middle-aged to older patients • Other Types: Gestational Diabetes during pregnancy

  3. Blood Glucose • Insulin • hormone that circulates in the blood • helps body use and store glucose • Low levels of insulin: body cannot store glucose • After eating, blood glucose rises as food is broken down • High blood glucose levels damage the eyes, kidneys, nerves, and heart over time • Normal glucose levels: 82 to 110 mg/dL

  4. Management of Diabetes • Diet • Exercise • Oral Medication • Insulin Therapy: injection of exogenous insulin analogs when blood glucose levels are high

  5. Electrochemical Glucometers • Measure glucose in blood • At home testing requires minimal amounts of blood • Utilizes disposable electrochemical cell • electrical current is created from the oxidation of glucose Type I check 4 times/day Type II check 2 times/day

  6. Traditional Electrochemistry H2 gas Components • Working electrode: Silver electrode • Where reaction of interest takes place • Reference electrode: Standard hydrogen electrode • Measure current flowing between electrodes Cl- Ag+

  7. Chemical Reactions Oxidation of Glucose by Enzyme glucose +GOD(ox) gluconolactone + GOD(red) glucose gluconolactone + 2e- 2e- + GOD(ox) GOD(red) D-glucose Glucose Oxidase (GOD) is an enzyme directly oxides Glucose Reduction of Enzyme by Mediator GOD(red) + 2Fecp2R+GOD(ox) + 2Fecp2R + 2H+ 2Fecp2R 2Fecp2R + 2e- Ferrocenemonocarboxylic acid (Fecp2R) Mediator transports electrons to working electrode

  8. Test Strips • When blood added, glucose is oxidized by enzyme coated on working electrode • Voltage applied between working and reference electrode • Measure current between working and reference electrode

  9. Amperometric Analysis • Current measured 5-15 seconds after blood is drawn • Current levels directly proportional to glucose levels Calibration curve for glucose enzyme electrode in (*) argon, (0) air, and (+) oxygen-saturated buffer. Steady-state current was measured at 160 mV vs. SCE, pH 7.0, and 25 OC.

  10. Advantages Fast Disposable Strip No Instrument Contamination Disadvantages • Discomfort of pricking finger • Non-continuous measurement

  11. Implantable Glucose Sensor • Advantage: continuous glucose monitoring • Could be coupled with continuous subcutaneous insulin infusions • Problems: • Sensor stability • Calibration • Biocompatibility

  12. Recent Study Designed Implantable sensor recorded glucose values every 128 s Longest sensor (of 5 subjects) lasted 103 days in vivo!

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