Biosensor

Biosensor

Biological and biochemical processes have a very important role on medicine, biology and Biotechnology.  The first biosensor was described in 1962 by Clark and Lyons who immobilized glucose oxidase (GOD). According to a recently proposed IUPAC definition , “ A biosensor is a self-contained integrated device which is capable of providing specific quantitative or semi-quantitative analytical information using a biological recognition element (biochemical receptor) which is in direct spatial contact with a transducer element.”

A biosensor is a device composed of these elements:

1. A bioreceptor that is an immobilized sensitive biological element (e.g. enzyme, DNA probe, antibody) recognizing the analyte (e.g. enzyme substrate, complementary DNA, antigen). Although antibodies and oligonucleotides are widely employed, enzymes are by far the most commonly used biosensing elements in biosensors.

2.  A transducer is used to convert (bio)chemical signal resulting from the interaction of the analyte with the bioreceptor into an electronic one. The intensity of generated signal is directly or inversely proportional to the analyte concentration. Electrochemical transducers are often used to develop biosensors. These systems offer some advantages such as low cost, simple design or small dimensions. Biosensors can also be based on gravimetric, calorimetric or optical detection.

3.An Electronic Amplifier is an electronic device that increases the power of a signal.

4. A Data processing system is a combination of machines that for a set of inputs produces a defined set of outputs. The inputs and outputs are interpreted as data, facts, information, ... depending on the interpreter's relation to the system.

Characteristics of a Biosensor

1.)    Selectivity: Selectivity means that sensor detects a certain analyte and does not react with added mixtures and contaminants.

2.)    Precision: is the degree to which repeated measurements under unchanged conditions show the same results.

3.)    Signal stability : signal drift under constant conditions, which causes an error in measured concentration.

4.)    Sensitivity (detection limit): the minimal amount (or concentration) of analyte that can be detected.

5.)    Working range : range of analyte concentrations in which the sensor can operate.

6.)    Regeneration time : time required to return the sensor to working state after interaction with the sample.

Applications:

The application of biosensor areas  are clinic, diagnostic, medical applications, process control, bioreactors, quality control, agriculture and veterinary medicine, bacterial and viral diagnostic, drug production, control of industrial waste water, mining, military defense industry  etc.

A few advantages of biosensors are listed below:

1. They can measure nonpolar molecules that do not respond to most measurement Devices.

2. Biosensors are specific due to the immobilized system used in them

3. Rapid and continuous control is possible with biosensors

4. Response time is short (typically less than a minute) and

5. PracticalThere are also some disadvantages of biosensors:

1. Heat sterilization is not possible because of denaturaziation of biological material,

2. Stability of biological material (such as enzyme, cell, antibody, tissue, etc.), depends on the natural properties of the molecule that can be denaturalized under environmental conditions (pH, temperature or ions).

3. The cells in the biosensor can become intoxicated by other molecules that are capable of diffusing through the membrane.

Thévenot‟s definition of a chemical biosensor from 2001 is often quoted in biosensor research: “An electrochemical biosensor is a self-contained integrated device, which is capable of providing specific quantitative or semi-quantitative analytical information using a biological recognition element (biochemical receptor) which is retained in direct spatial contact with an electrochemical transduction element.” (The first biosensor was developed in 1962 by Clark and Lyon as an „enzyme electrode‟ for the measurement of glucose levels.)

Biosensor signal detection methods

1.)    Amperometry is operated at a given applied potential between the working electrode and the reference electrode, and the generated signal is correlated with the concentration of target compounds. In the amperometric detection, the current signal is generated as a function of the reduction or oxidation of an electro-active product on the surface of a working electrode.

2.)    Conductometry is a technique depending on the conductivity change in the solution due to the production or consumption of ions, for example, by the metabolic activity of microorganisms. poor.

3.)    Potentiometry involves the measurement of the potential difference between the working electrode and the reference electrode which is dependent on concentration-related behavior.

4.)    Voltammetry is the most versatile technique in electrochemical analysis. Both the current and the potential are measured. The position of peak current is related to the specific chemical and the peak current density is proportional to the concentration of the corresponding species.

5.)    Optical detection is usually based on the measurement of luminescent, fluorescent, colorimetric, or other optical signals produced by the interaction of microorganisms with the analytes and correlates the observed optical signal with the concentration of target compounds.