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BIOSENSORSBIOSENSORS

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INTRODUCTIONINTRODUCTION What Is a Biosensor?

Biosensor = bioreceptor + transducer.

The bioreceptor is a biomolecule that recognizes

the target analyte whereas the transducerconverts the recognition event into a measurablesignal.

Enzyme is a Bioreceptor

Requirements for Sensors

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Need for Biosensor

Diagnostic MarketThe current climate of prevention the need for detection

at increasingly lower limits is increasing in many diverseareas

Clinical Testingclinical testing is one of the biggest diagnostic markets

clinical testing products market in excess of 4000 million US$

in the 1990s

Other MarketsThe medical arena (Technical Insights Inc.) with

veterinary and agricultural applications

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SpecificityWith biosensors, it is possible to measure specific

analytes with great accuracy.

Speed

analyte tracers or catalytic products can be directlyand instantaneously measured

Simplicityreceptor and transducer are integrated into one

single sensor& the measurement of target analytes withoutusing reagents is possible

Continuous monitoring capabilityBiosensors regenerate and reuse the immobilized

biological recognition element

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Applications of Biosensor

Health Care Measurement of Metabolites

Market Potential

Diabetes

Insulin Therapy Artificial Pancreas

Industrial Process Control Bioreactor Control

Military Application Environmental Monitoring

Air and Water Monitoring

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Bioreceptor Molecules

Enzymes

Enzymes act as catalysts for biochemical reactionsoccurring in the cell

AntibodyAntibodies constitute about 20% of the total plasma

protein and are collectively called immunoglobulin

Receptor Protein

Receptor proteins having specific affinity forhormones, antibodies, enzymes

Other Possibilities

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Transducers

Conventional Transducers

Piezoelectric Transducers

Coniductimetry

Capacitance Measurement

Thermometry

Enzyme Thermistor

FET as a Transducer

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Receptors Receptors at Membrane

Biological receptors are protein molecules most of

them are bound to the cell membrane

Hormone Receptors

Many hormones released into the blood do not

penetrate the cell membrane but react with specific

receptors at the cell surface

Smell Receptor

taste and olfactory receptors are typical examples of

this biospecific recognition process

Light Receptor

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Types of biosensor

Glucose Biosensor

Amperometric BiosensorGlucose biosensor using glucose oxidase is used as an example

Potentiometer BiosensorExamples of Potentiometric Biosensor

Penicillin biosensorGlucose biosensor

Urea biosensor

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Design Variables

Immobilization Methods

(1) adsorption

(2) entrapment

(3) covalent coupling

(4) cross-linking

Change in Conformation

Change in Microenvironment Non-Uniform Distribution

Reaction and Diffusion

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Future Prospects

Data Processing and PatternRecognition

Micro Instrument Molecular Electronics

Multi-Disciplinary Nature

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CONCLUSION

Biosensors consist of bio-recognition systems, typicallyenzymes or binding proteins, such as antibodies,immobilized onto the surface of physico-chemicaltransducers

Disadvantages

They cannot be steam sterilized

They react with the product

And are oversensitive