Bio sensor is a device which converts the biological signal or response into electrical signal. A biosensor is a device that used to detect record and also transmit information regarding a physiological change or the presence of various biological or chemical materials present in the environment. Technically speaking biosensor is a probe that integrates biological components with an electronic component so that we can get a measurable signal. Biological components may include a whole bacterial cell or biological products such as antibody or an enzyme.

Characteristics of Biosensors:

1. Biosensors are highly specific
2. Reaction are independent of physical parameters such as temperature, pH
3. Biosensors are biocompatible
4. Biosensors are economical
5. Biosensors should have market value
6. Biosensors should be precise and accurate

Carbon Nanotubes:

Carbon nanotubes are made up of carbon atoms which are rolled into sheet of 1 nanometer. In these nanotubes light is emitted after absorbing light in infrared region. As wavelength of infrared light are not blocked by body fluid, therefore this nanotubes are used to get information about the body. These carbon nanotubes are constructed in such a way that when they bind to target compounds, there is change in fluorescence dimension, this helps in identifying molecule present in the body.

Types of Biosensors:

1. Optical biosensors: Technique used in this biosensor is based on surface plasma resonance.

2. Electrochemical sensing biosensors: Technique used in this biosensor is based on amperometric sensing, conductimetric sensing.

In amperometric sensing, increasing potential is applied to the cell until oxidation of the substance to be analysed occurs. This in turn increases the cell current and gives a peak current. The height of this peak current will be directly proportional to the concentration of electroactive substances or molecules.
In conductive sensors substrate concentration is measured using relationship between conductance and concentration of ionic species.

3. Enzymatic biosensors: This type of sensors is widely used as they are easy to use. For example glucose biosensors.

In glucose biosensor enzyme acts as a biorecognition element and recognizes only the glucose molecule. These enzymes are present in the electrode surface. When enzyme recognizes the glucose molecule it act as biocatalyst and produces gluconic acid and hydrogen peroxide using glucose and oxygen from the air. This reaction leads to the flow of electrons from hydrogen peroxide/oxygen coupling. This flow of electron is directly proportional to the number of glucose, molecules present in the biological fluid such as blood.

Applications of Biosensors:

Biosensors are used in various fields such as food industry, environmental field, medical care both in clinical as well as laboratory use, and also in biotechnology fields.

1. Environmental field:
a. Biosensors are used in detecting environmental pollutants.
b. Biosensors are used for measuring concentration of various metal ions by specific protein concentration or by using genetically modified organisms.
c. Biosensors are used in the BOD measurement during waste water treatment.
d. Biosensors are used in the detection of polyaromatic hydrocarbons present in water.

2. Food industry:
a. Biosensors are used in determining the quality of the food.
b. Biosensors are used in monitoring key analysts like glucose.
c. Biosensors are used for detection of biogenic amines or in other words food freshness marker determining parameters in wine industry.
d. Biosensors are used in controlling the industrial processes.

3. Biosensors used in process control will be able to measure materials present in the process flow of temperature, pressure and also the acidity readings.

4. Use of biosensors in industry will improve manufacturing techniques, this will allow for usage of wider variety of sensing molecules.

5. Biosensors are used in both clinical and laboratory use in medical care.

6. Tumor cells are used as biosensors to monitor the susceptibility of chemotherapeutic drugs.

7. Biosensors are also used to monitor the manufacturing of pharmaceutical compounds.

8. Biosensors are used in organ replacement procedures such as an artificial pancreas replacement in patient with diabetes.

9. Biosensors are also used in medical research.

10. Biosensors are used in monitoring of the glutamate and acetyl choline, which is the main cause in neurodegenerative diseases.

11. Biosensors are used in analysing microdialysis samples.

12. Biosensors are used in biotechnological process such as to determine proteins or peptides.

13. Biosensors are also used in determining intracellular proteins and also plasmids.

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