Glucose Dipstick & Biosensor

S(f) Explain the principles of operation

Quantitative measurement of glucose

A diabetic patient: blood glucose level > 4.7 mM Urine glucose level > 11 mM

Need a rapid test to monitor

when & how much insulin

needs to be injected.

Glucose Dipstick

Glucose Dipstick - principles

Glucose Biosensor

Biosensor – principles

Five major parts:1. Selectively permeable membrane

2. Biological recognition layer

3. Transducer

4. Amplifier

5. Signal processing system

Glucose Biosensor – principles

At biological recognition layer:

Glucose + O2 + H2O

glucose oxidase

gluconic acid + H2O2

At negative electrode:

O2 +4e- +4H+ 2H2O

electric signal

digital readout

Biosensor - Advantages

Can detect specific molecule in a mixture Very sensitive,

can detect small sample and [low] Rapid in response Safe to use Accurate Small Can be mass produced.

Biosensor - Disadvantages

need careful handling not very stable not sterilisable

Figure- Cyanide biosensor

Biosensor Applications

Medical Cholesterol & alcohol measurement

Food industry Microbial detection in meat,

dairy products & water Agriculture

Pesticides, crop disease, ripeness, nutrients Environment

Air and water pollutants

Food Safety Biosensor

Biosensors in Agriculture

Water Toxicity Biosensor

Principles of Glucose Dipstick & Biosensor (recap) Glucose dipstick

Immobilised enzymes react with glucose molecules, product is coloured.

Glucose biosensor 1. Selectively permeable membrane2. Biological recognition layer3. Transducer4. Amplifier5. Signal processing system