1. Biosensors Definition
An analytical device, which is a combination of biological component with a physicochemical detector used for the sensing an analyte (biological samples)
Converts biological response into electrical signals

2. Working Principle Enzyme substrate specificity
Bio & Sensor elements coupled by Membrane & Matrix Entrapment (Fig. – 3), Physical adsorption, Covalent Bonding
Fig. - 1
Fig. - 3
Fig. - 2

3. Components of Biosensors1 2 3
Analyte
Bioelement
Transducer
Conductimetric
1. Electrochemical Biosensors
Amperometric
Potentiometric
2. Ion - Sensitive Biosensors
3. Thermal - Detection Biosensors
4. Optical – Detection Biosensors
5. Resonant Biosensors

4. Resonant/ Piezoelectric Biosensors
Analyte - Antigen
Bioelement – Antibody
Transducer – Acoustic wave transducer
Signal – Change in frequency/mass measured

5. Optical Detection Biosensor
Analyte - Antigen
Bioelement – Antibody
Transducer – Silicon wafer exposed to UV light
Signal – Light measured
UV light

6. Thermal Detection Biosensor
Analyte - Antigen
Bioelement – Immobilized enzyme
Transducer – Thermistor
Signal – Heat measured

7. Ion Sensitive Biosensor (ISFET)
Analyte – Antigen (Ion)
Bioelement – Antibody
Transducer – Semiconductor – Field Effect Transistor (FET)
Signal – pH change measured

8. Electrochemical Biosensors
Conductimetric
Amperometric
Potentiometric
Glucose Biosensors
Principle – Change in chemical reaction produce or consume ions/ electrons, which causes electrical change and it is measured.
Glucose biosensors first invented by Leland C. Clark (Used Platinum eletrodes)

9. Glucose Biosensors Analyte – Glucose (Substrate)
Bioelement – Immobilized Enzyme Membrane – Glucose Oxidase (GOD)
Transducer – Graphite electrode
Signal – Change in chemical ion measured
Strip – Glucose Oxidase GOD
GOD reacts with glucose and produce gluconic acid
More glucose, more oxygen is consumed
Less glucose, more hydrogen peroxide is consume
A mediator replaces oxygen, accepting the electron and passes to the electrode
This generates current
This current is reported as glucose concentration

10. Application DNA Detection
Uses – Detection of Anthrax, Botulinum, Harmful pathogens
Objective – Isolate single DNA-DNA, Antigen-antibody bond
Methods
1. Polymerase Chain Reaction (PCR) – multiple copies of DNA
2. Force Amplified Biological Sensor(FABS)
3. Force Differentiation Assay (FDA)
4. Bead Array Counter (BAC)

11. Application Pollution Detection
Uses – Detection of specific xenobiotic pollutants
Objective – Isolate specific pollutants, ex; lux gene coupled ( rDNA technology) - reporter gene - fluorescence
Methods
1. Spectrometry (UV, IR, Visible)
2. Chromatography (GC, TLC, HPLC)
3. Immunoassay (ELISA)
4. Monoclonal antibodies

12. Application Food Industry Uses Measurement of carbohydrates, alcohols
Sterility, food safety in meats, beverages (Beer, soft drinks) etc.
Objective – Used in quality assurance
Methods
1. Flow injection system