Biosensor

Biosensors are analytical devices which use biological interactions to provide either qualitative or quantitative results

(2) Other biorecognizing molecules (= bioreceptors) include antibodies, nucleic acids,

(1) A transducer should be capable of converting the biorecognition event into a

(2) Typically, this is done by measuring the change that occur in the bioreceptor reaction.

(3) For example, the enzyme glucose oxidase (used as a bioreceptor in a glucose biosensor)

Considerations in Biosensor Development

The major tasks in developing a biosensor for a target analyte and the necessary

skills involved are:

1. Selection of a suitable bioreceptor molecule -

Requires knowledge in biochemistry and biology

2. Selection of a suitable immobilization method –

Requires knowledge in chemistry

3. Selection of a suitable transducer –

Requires knowledge in electrochemistry and physics

4. Designing of biosensor considering measurement range, linearity,

and minimization of interference –

Requires knowledge in kinetics and mass transfer

5. Packaging of biosensor - Once a biosensor has been designed, it has to be put into a

package for convenience manufacturing and use. The current trend is

miniaturization and mass production. Modern IC (integrated circuit)

fabrication technology and micromachining technology are

used increasingly in fabricating biosensors.

Potential Applications of Biosensor

Commercial Requirements for Sensors

To be commercially successful, a biosensor has to meet the general

requirements of commercial sensors. These are:

      1. Relevance of output signal to measurement environment
      2. Accuracy and repeatability
      3. Sensitivity and resolution
      4. Dynamic range
      5. Speed of response
      6. Insensitivity to temperature (or temperature compensation)
      7. Insensitive to electrical and other environmental interference
      8. Amenable to testing and calibration
      9. Reliability and Self-Checking Capability
     10. Physical robustness
     11. Service requirements
     12. Capital cost
     13. Running costs and life
     14. Acceptability by user
     15. Product safety-sample host system must not be contaminated by sensor

Amperometric Biosensors

1. High sensitivity, selectivity, and ability to operate in turbid solutions

are advantages of electrochemical biosensors.

2. Amperometric detection is based on measuring the oxidation or reduction

of an electroactive compound at a working electrode (sensor).

3. A potentiostat is used to apply a constant potential to the working

electrode with respect to a second electrode (reference electrode).

First Generation Amperometric Biosensor

Proposed by Clark and Lyons and implemented by Updike and Hicks, who coined the term enzyme electrode

In the 1970s, Yellow Springs Instruments (Yellow Springs, OH) was the first company to successfully market an amperometric biosensor