Biosensors

analytical device

1. Biosensors Subhananthini jeyamurugan 18py17 II M.Sc., Microbiology

2. WHAT IS BIOSENSOR? A biosensor is an analytical device which converts the biological signal into a measurable electrical signal.

3. Professor Leland C Clark is the father of Biosensor Professor Leland C Clark (1918–2005)

4. A good biosensor… It should provide accurate, precise, reproducible results. It should be free from electrical noise . It should be cheap, small, portable and capable of being used by semi-skilled operators. The reaction should be independent from physical parameters (stirring, pH and temperature ).

5. Parts of biosensor

6. Parts of biosensor Bio receptor Transducer Signal processor

7. Elements of biosensor

8. Biosensor

9. THE ANALYTE (What do you want to detect?) Molecule (Protein , toxin, peptide, vitamin, sugar, metal ion)

10. Bioreceptor The bioreceptor is a biologically derived material such as tissue, microorganisms, organelles , cell receptors, enzymes, antibodies , nucleic acids, etc…

11. Transducer When the analyte interacts with the bioreceptor, change in biological signals such as change in temperature , electrical charge occurs . The transducer transforms these signal into another signal which is easily measured and quantified .

12. WORKING OF BIOSENSOR Figure:- Schematic Diagram of a Biosensor

13. Based on the type of transducer the Biosensor are classified as  Calorimetric/Thermal Detection Biosensors.  Optical Biosensors.  Resonant Biosensors.  Piezoelectric Biosensors.  Ion Sensitive Biosensors.  Electrochemical Biosensors. Conductometric Sensors . Amperometric Sensors . Potentiometric Sensors.

14. Calorimetric biosensors The heat produced (or absorbed) by the reaction.

15. Thermal biosensor Enzyme thermistors are biosensors that use thermal resistors to measure the heat change caused by an enzymatic reaction.

16. Calorimetric / Thermal Detection Biosensors . Advantages : No need of Frequent recalibration. Insensitive to the Optical & Electrochemical Properties of the sample. Uses: Detection of: (1) Pesticides . ( 2) Pathogenic Bacteria.

17. O ptical biosensors In optical biosensors, antibiotics or enzymes are used as biological component , and light emitting diode, an optical fibre and a photodiode are used as a physical components . One end of the optical fibre has a coating of an ionophore plastic which selectively picks up specific ions in the analyte. There is a light detector called “photodiode” at the other end of the optical fibre. A monochromatic light is generated using the light emitting diode and passed through the ionophore plastic and optical fibre . Evanescent waves develop on the fibre. The waves reaching the detector are measured. Then the analyte is kept in contact with the ionophore plastic . The test molecules adsorbed on the plastic. They change the optical density of light . The difference in light absorption is detected, displayed, and recorded.

18. Optical biosensors

19. Optical Biosensors. Colorimetric for colour Measures change in Light Adsorption. Photometric for Light Intensity Detects the Photon output.

20. RESONANT BIOSENSORS In this type of biosensor, an acoustic wave transducer is coupled with an antibody (bio-element ). An Acoustic Wave Transducer is coupled with Bio element . Measures the change in Resonant Frequency.

21. Piezo-electric biosensors Effects due to the mass of the reactants or products .

22. ION-SENSITIVE BIOSENSORS An ISFET is an ion - sensitive field-effect transistor , that is a field-effect transistor(FET) used for measuring ion concentrations in solution ; when the ion concentration (such as H + , see pH scale) changes, the current through the transistor will change accordingly.

23. ION-SENSITIVE BIOSENSORS Are semiconductor FETs(field effect transistor) with ion-sensitive surface. Surface Electrical Potential changes when the ions &semiconductors interact. Measures the Change in Potential. Uses : pH Detection.

24. This type of biosensors has a semiconducting device called field effect transistor( FET). FET consists of silicon crystals . It has high electrical resistance unless the electric field is modified. When an analyte is kept in contact with FET . Some ions in the analyte adsorbed onto the silicon crystal and create an electrical charge. This electrical charge switches on the FET to conduct the electric charge to the transducer. From the transducer, electric signals are amplified , read out and recorded.

25. Ion sensitive membrane on the FET can be replaces by an enzyme immobilized membrane . Such FET is called enzyme FET or ENFET. Here the immobilized enzymes converts the test molecules into ionic forms . Electric charge of the ions are conducted to the transducer. They are used for monitoring ion concentration in many fermentation processes .

26. Enzyme electrodes In this type of biosensors, an enzyme is immobilized onto the surface of an electrode. The enzyme catalyzes its specific reaction and thus transfers electrons from the reactants to the electrode . Current generated on the electrode is amplified , read out and recorded. Types Conductimetric BioSensors. Amperometric Biosensors. Potentiometric Biosensors.

27. Enzyme electrodes Uses : Detection of : Hybridized DNA DNA- binding Drugs & Glucose Concentration .

28. Conductometric BioSensors Measures Electrical Conductance/Resistance of the solution.

29. Amperometric biosensors In this type of biosensors, current generated in the electrode is measured with a millivolt-ammeter . The electrode consists of a platinum and silver peroxide cathode. T he cathode is placed in 0.1m phosphate buffer . An appropriate enzyme is immobilized on the anode using an acetyl cellulose membrane. The two electrodes are connected with a millivolt ammeter. when the anode is kept dipped in an analyte , the voltage is near zero (i.e.0.02µA). Then a redox dye ( e.g 2-6- dichloraphenolindophenol ) or mediator ( eg . Ferrocene ) is added to the analyte. The enzyme catalyses its reaction and transfers electrons to the electrode. The electric current is conducted to the transducer.

30. Amperometric biosensors Movement of electrons produced in a redox reaction.

31. Potentiometric biosensors In this sensors, the electrode is held at a voltage which counteracts the electrons generated by the enzyme reaction. the voltage supplied to adjust the current not to flow, is measured and recorded . Many enzyme electrodes are made to analyse amines, cholesterol, carbon monoxide, glucose, penicillin and uric acid . Cholesterol sensor has the enzyme cholesterol oxidase, glucose sensor is made with the enzyme glucose oxidase. Uric acid sensor has the enzyme uricase . These biosensors are used to analyse blood samples .

32. Potentiometric biosensors Changes in the distribution of charges causing an electrical potential.

33. ADVANTAGES Highly Specific . Independent of Factors like stirring, pH, etc . Easy to Use , Durable . Require only Small Sample Volume. Rapid , Accurate , Stable & Sterilizable .

34. Applications

35. Food Analysis. Study of Biomolecules & their Interaction . Drug Development. Crime Detection. Medical Diagnosis ( Clinical laboratory). Environmental Field Monitoring. Quality Control. Industrial Process Control . Manufacturing Of Pharmaceuticals & Replacement organs .

36. Biosensor for agricultural and food industry Detection of viral , fungal , bacterial diseases of plants . In food industry, detection of total microbes and food quantification in soft drinks. To determine the freshness of fish , beef and other food items.

37. In medicine… A glucose biosensor coupled with a minipump containing insulin , is used to detect blood glucose level directly and to deliver the accurate amount of insulin required by the diabetic. Usually enzyme electrode is used for this purpose. Biosensors are used to detect mutagenic substances ( eg . Mitomycin ) in the body fluid. A few biosensors are employed to detect toxic substances and heavy metals in blood samples .

38. Thank you for your attentions…