- Diabetes is a chronic metabolic disease effecting millions
worldwide. Diabetes is categorized by:
- Type I (Juvenile Diabetes): Pancreas produces very little or
- Type II (Insulin Resistant): Pancreas does not produce
insulin or does not use produced insulin effectively (insulin resistant)
- Other Types: Gestational Diabetes during pregnancy
- Insulin is a circulating hormone that helps the body use and
glucose. At low levels of insulin, the body stores less nutrients
in the formof glucose
- After eating, blood glucose rises as food is broken down.
blood glucose levels damage the eyes, kidneys, nerves, and heart over
- Diabetics aim to keep their blood glucose level within normal
to 110 mg/dL). Insulin therapy is a common method in which
exogenous insulin analogs are injected when blood gluose are high
Example home glucometer
- At home glucometers allow diabetic patients to monitor
glucose levels with a minimal amount of sample blood.
utilize disposable electrochemical cells.
- Type I diabetics check their blood glucose levels about 4
- Type II diabetics check their blood glucose levels about 2
Components of a typical galvanic electrochemical cell:
Current flowing between electrodes can be measured using a
- Working electrode: reaction of interest takes place
- example: silver electrode
- Reference electrode: standard hydrogen electrode
composing of working electrod,
reference electrode, and
Step 1: Oxidation of Glucose by Enzyme
Glocuse Oxidase (GOD) is an enzyme
that directly oxides glucose
Step 2: Reduction of enzyme by Mediator
An example of a mediator is
ferrocene monocarboxylic acid.
- When blood added, glucose is oxidized by enzyme coated on
- Voltage applied between working and reference electrode
- Measure current between working and reference electrode
Example Testing Strip
(left) composing of all necessary components.
- Current measured across the test
strip 5-15 seconds after blood is drawn
- As seen on the calibration curve to the right, current
proportional to glucose levels.
Ampometric Analysis Output
(left) 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 degrees Celcius. (Cass 1984)
- Disposable Strip
- No Instrument
- Discomfort of pricking finger
- Non-continuous measurement
- Implantable electrochemical glucometers would allow for
measurement of blood glucose levels.
- This technology has the
potential of being couple with continuous subcutaneous insulin
infusions which could deliver insulin to a patient automatically.
- In a recent study by Barbara Gillian et. al. was able to
implantable electrochemical glucosensor that lasted over 100 days in
- In this study, the designed glucosensor was able to record
glucose levels every 128 seconds and were highly corelated with lab
monitors and two common glucose monitors (see left).
- While implantable glucosensors show promise, problems arise
- Sensor stability
- Biocompatability (rejection): Immunoresponse from the body
can destroy implanted sensors.
Cass, Anthony E. G. "Ferrocene-mediated
enzyme electrode for amperometric determination of glucose.
Analytical Chemistry. (1984)56:667-671
Heller, A. and B. Feldman. "Electrochemical
glucose sensors and their applications in diabetes management
Chemical Reviews. (2008)108: 2482-2505
Gilligan, Barbara J. et. al. "Feasibility
of Continuous Long-Term Glucose Monitoring from a Subcutaneous Glucose
Sensor in Humans
" Diabete Technology &
Leary and Skoog. Principles of Instrumental Analysis.
Orlando: Sauders College Publishing (1992)
Newman, Jeffery D. and Anthony P.F. Turner. "Home
blood glucose biosensors: a commercial perspective.