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
– 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
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
Management of Diabetes
• Diet
• Exercise
• Oral Medication
• Insulin Therapy: injection of
exogenous insulin analogs
when blood glucose levels
are high
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
Traditional Electrochemistry
Components
• Working electrode: Silver
electrode
H2 gas
– Where reaction of interest takes
place
• Reference electrode: Standard
hydrogen electrode
• Measure current flowing
between electrodes
Cl-
Ag+
Chemical Reactions
OXIDATION OF GLUCOSE BY ENZYME
glucose + GOD(ox)  gluconolactone + GOD(red)
glucose  gluconolactone + 2e2e- + 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 + 2eFerrocene monocarboxylic acid
(Fecp2R)
Mediator transports electrons to working electrode
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
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.
Advantages
Fast
Disposable Strip
No Instrument Contamination
Disadvantages
Discomfort of pricking finger
Non-continuous measurement
Implantable Glucose Sensor
• Advantage: continuous glucose monitoring
– Could be coupled with continuous subcutaneous
insulin infusions
• Problems:
– Sensor stability
– Calibration
– Biocompatibility
Recent Study
Designed Implantable sensor recorded glucose values every 128 s
Longest sensor (of 5 subjects) lasted 103 days in vivo!