Biomedical Engineering Reference
In-Depth Information
FIGURE 10.34
Principle of a glucose sensor.
product that is formed (or consumed) is usually detected by an ion-selective electrode.
A membrane separates the basic sensor from the enzyme if a gas is consumed (such as
O
2
) or is produced (such as CO
2
or NH
3
). Although the concentration of the bulk substrate
drops continuously, the rate of consumption is usually negligible. The decrease is detected
only when the test volume is very small or when the area of the enzyme membrane is large
enough. Thus, this electrochemical analysis is nondestructive, and the sample can be
reused. Measurements are usually performed at a constant pH and temperature either in
a stirred medium solution or in a flow-through solution.
10.5.2 Microbial Biosensors
The fundamental basis of a microbial biosensor is the close proximity between an immo-
bilized microorganism that serves as a specific recognition element and an electrochemical
or optical sensing transducer that is used to convert the biochemical signal into an elec-
tronic signal that can be processed.
The fabrication of a microbial biosensor requires the immobilization of the microorgan-
isms on a transducer by chemical or physical methods. Since the response, operational sta-
bility, and long-term use of a microbial biosensor is a function of the immobilization
strategy used, immobilization technology plays a very important role in the successful
design of microbial biosensors, and the choice of immobilization technique is critical.
