Tuesday, April 11, 2023

Jalpan J.ShahS.Y.Bsc(Biotech)

Roll No.48Government

Science CollegeKhokhara,

Ahmedabad

BIOSENSORIntroductionIntroduction

Different types of biosensorDifferent types of biosensorApplications of biosensorApplications of biosensor

What is Biosensor??

It consists of 3 parts: the sensitive biological element [biological material (eg.

tissue, microorganisms, organelles, cell receptors, enzymes, antibodies, nucleic acids, etc), a biologically derived material or biomimic] The sensitive elements can be created by biological engineering.

the transducer or the detector element (works in a physicochemical way; optical, piezoelectric, electrochemical, etc.) that transforms the signal resulting from the interaction of the analyte with the biological element into another signal (i.e., transducers) that can be more easily measured and quantified;

associated electronics or signal processors that is primarily responsible for the display of the results in a user-friendly way.

Schematic Diagram of Biosensor

Schematic diagram showing the main components of a biosensor. The biocatalyst (a) converts the substrate to product. This reaction is determined by the transducer (b) which converts it to an electrical signal. The output from the transducer is amplified (c), processed (d) and displayed (e).

A glucose electrode

Mechanism of a glucose electrode Glucose soln is brought into the contact of mambrane Glucose & oxygen pass through membrane into the enzyme layer & as

a result of oxidation reduction reactions,converted into gluconic acid & hydrogen peroxide in the presence of water,oxygen & glucose oxidase.

Consequently,oxygen conc.in the gel around electrode is lowered down. H2O2 brings about a change in current i.e.measurable signal. Electrode

records the rate of reaction. The rate of diminition of oxygen conc.is proportional to glucose conc.of

the sample.

Cellulose acetate membranePermeable teflon membrane

Ring seal

Saturated KCl solution

Platinum O2 electrode

Glucose soln

Something more about glucose electrode…

In 1987,for the first time Yellow Springs Instruments Co.,USA developed a biosensor for a diagnostic purposes for measuring glucose in blood plasma.

It is a hand-held machine which measures six components of blood plasma for example Glucose,Urea,Nitrogen,Sodium,Potassium & Chioride.

An indigenous glucose sensor has been developed by the scientists at Central Elecro-chemical Research Institute(CECRI),Karaikudi.

It gives electic signal for a glucose conc. as low as 0-15 millimoles.

Different types of Biosensor

Biosensors are of different types based on the use of different biological material & sensor devices, a few of them are as under:

1. Electro-chemical Biosensor2. Amperometric Biosensor3. Thermistor containing Biosensor4. Bioaffinity sensor5. Whole cell(Microbial) Biosensor6. Opto-electronic Biosensor

Electro-chemical Biosensor

This type of biosensor has been developed by using electronic devices such as field effect transmitors or light emitting diode; the former measures charge accumulation on their surface & the later photoresponse generated in a silica based chip as an alternating current.

Hence, the field effect transmitor measures a biochemical reaction at the surface & induce into current.

Moreover, the field effect transmitors can be modified to ion sensitive, enzyme sensitive OR antibody sensitive ones by using selective ions, enzyme or antibodies respectively.

1

Amperometric biosensor

Amperometric biosensors are those which measures the reaction of anylate with enzyme & generate electrons directly or through mediator.

electrode

Redox-mediator

enzyme

product

substratee-

e-

e-

In this biosensor,a redox reaction catalysed by an enzymes is directly coupled to an electrode where enzyme is presentd with the oxidizable substrate.

2

Thermistor containing Biosensor

Thermistor is used to record even a small temperature changes (between 0.1-0.001°C) during biochemical reactions.

By immobilizing enzymes like cholesterol oxidase, glucose oxidase, invertase, tyrosinase, etc.thermistors have been developed.

Moreover, thermistors are also employed for the study of antigen-antibody with very high sensitivity in case of thermometric Enzyme Linked Immunoabsorbent Assay(ELISA).

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Bioaffinity sensor

Bioaffinity sensors are developed recently. It measures the conc.of the determinants.i.e. substrate based on equilibrium binding. This shows a high degree of selectivity.

These are of diverse nature because of the use of radiolabelled, enzymelabelled or fluorescencelabelled substance.

transducer

Determinant analogue

Labelled receptor

determinant

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fig. Principle of Bioaffinity sensor

Working of bioaffinity biosensor

In this biosensor, a receptor is radiolabelled & allowed to bind with determinant analogue immobilized onto the surface of a trasducer.

When conc.of a determinant are increased,the labelled receptor forms an intimately bound complex with determinant.

Finally,radiolabelled receptor-determinant complex is removed from the immobilized determinant analogue resulting in the increased conc.of labelled receptor.this is measured by a reduction in signal of the labelled receptor.

Gronow(1988) have discussed that the possibilities of this type of biosensors are the use of..

ReceptorsReceptors Estimation Estimation Lectin saccharide Hormone hormone Drug drug Antibody antigen Nucleic acid inherited disease &

fingerprinting

Whole cell Biosensors(Microbial Biosensors)

In this device,either immobilized whole cell of microorganisms OR their organelles are used.

These react with a large number of substrates and show generally slow response.

Immobilized Azotobacter vinelandii coupled with ammonia electrode shows sensitivity range between 10 ֿ & 8×10 mol dm ֿ .It measures the conc. of nitrate within 5-10 min ֿ .

Examples of microbial biosensors are given in the table.

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3

2

microorganis Sensoring for Response time(min)

range

Bacillus subtilis Mutagen sreening 90-100 1-6µg cm ֿ

Methylomonas flagellata methane 1 Upto 6.6 m mol dm ֿ

T.brassicae ethanol 10 Below 22.5 mg dm ֿ

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3

3

5

Opto-electric biosensor

In this biosensor either enzymes or antibodies are immobilized on the surface of a membrane.

For measuring colour,biosensor with enzyme and dye is immobilized to a membrane.

When a substrate is catalysed to yield product,changes in pH of the medium occur.

This results in changes in dye-membrane complex.

These changes in colour are measured by using a light emitting diode & a photodiode.

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Applications of Biosensor

In the beginning biosensor was applied in the field of medicine & industry. But in recent years,biosensors are becoming popular in many areas due to the

Small size Rapid & easy handling Low cost Greater sensitivity & selectivitySome of the areas is described as

below: Use in medicine & health Use in pollution control Use in industry Use in military

Some other Applications.. There are many potential application of biosensors of various

type. Glucose monitoring in diabetes patients <-- historical market

driver Other medical health related targets Environmental applications e.g. the detection of pesticides and

river water contaminants Remote sensing of airborne bacteria e.g. in counter-bioterrorist

activities Detection of pathogens. Determining levels of toxic substances before and after

bioremediation Detection and determining of organophosphate Routine analytical measurement of folic acid, biotin, vitamin

B12 and pantothenic acid as an alternative to microbiological assay

Determination of drug residues in food, such as antibiotics and growth promoters, particularly meat and honey.

Drug discovery and evaluation of biological activity of new compounds.

Detection of toxic metabolites such as mycotoxins.

references

http://www.schandgroup.comhttp://www.biosensor.comhttp://www.britanicca.com

Thanking you

Jalpan shahJalpan shah