Biosensor , its components, working and types of biosensors

Biosensor ;applications in biochemistry

1. BIOSENSOR ARYA H

2. Father of Biosensor – Professor Leland C Clark The term ‘biosensor’ is short for “biological sensor” Analytical device used for the detection of an analyte , that combines a biological component with a physicochemical detector. It is a device incoporating a biological sensing element either intimately connected to or integrated within a transducer

3. Recognition based on affinity between complementary structures like: Enzyme-substrate, antibody-antigen and receptor-hormone complex Selectivity and specificity depend on biological recognition systems connected to a suitable transducer.

4. It converts a response into an electrical signal It detects, records, and transmits information regarding a physiological change or process It determines the presence and concentration of a specific substance in an test solution Main features of biosensors are stability cost sensitivity reproducibility

5. Basic principle of biosensor Basic principle involved in three element :- First biological recognition element which highly specific towards the biological material analytes produces Second transducers detect and transduces signal from biological target – receptor molecule to electrical signal which is due to reaction occur Third after transduction signal from biological to electrical signal where its amplification is necessary and takes place and read out in detector after processing the values are displayed for monitor and controlling the system

6. Components of biosensors

7. Ist component – Biological element The component used to bind the target molecule Must be highly specific, stable under storage conditions and immobilized A variety of substance may be used as bioelement in biosensor Microorganism Tissue, Cell, Organelle Nucleic acid Enzyme, Enzyme component Receptor Antibody Plant proteins or lectins

8. Functions; To interact specifically with a target compound i.e the compound to be detected It must be capable of detecting the presence of a target compound in the test solution The ability of a bio-element to interact with target compound (specificity) in the basis of biosensor

9. 2 nd component – P hysiochemical Transducer Acts as an interface, measuring the physical change that occurs with the reaction at the bioreceptor then transforming that energy into measureable electrical output

10. 3rd component - Detector Signals from the transducer are passed to a microprocessor where they are amplified and analyzed. The data is then converted to concentration units and transferred to a display or / and data storage device

11. The block diagram of biosensor include three segments namely sensor, transducer and associated electrons. In the first segment the sensor is a responsive biological part Second segment is the detector part that changes the resulting signal from the contact of the analyte and for the results it displays in an accesible way The final section comprises of an amplifier which is known as signal conditioning circuit, the display unit as well as the processor.

12. Basic principle of Biosensor The biological material is immobilized and a contact is made between the immobilized biological material and the transducer The analyte binds to the biological material to form a bound analyte which inturn produces the electronic response that can be measured Sometimes the analyte is converted to a product which could be associated with the release of heat, gas(oxygen), electrons, hydrogen ions. The transducer then converts the product linked changes into electrical signals which can be amplified and measured

13. Working principle of B iosensor A nalyte diffuses from the solution to the surface of the biosensor Analyte reacts specifically and efficiently with the biological component of the biosensor This reaction changes the physicochemical properties of the transducer surface This leads to a change in the optical/ electronic properties of the transducer surface The changes in the optical/ electronic properties is measured/ converted into electrical signal, which is detected

14. Usually a specific enzyme or preferred biological material is deactivated by some of the usual methods and the deactivated biological material is in near contact to the transducer The analyte connects to the biological object to shape a clear analyte which in turn gives the electronic reaction that can be calculated In some examples, the analyte is changed to a device which may be connected to the discharge of gas, heat, electron ions or hydrogen ions In this the transducer can alter the device linked converts into electrical signals which can be changed and calculated

15. How does they work…?? Basically it involve the quantitative analysis of various substances by converting their biological actions into measurable signals Generally the performance of the biosensors is mostly dependent on the specificity and sensitivity of the biological reaction, besides the stability of the enzyme

16. Ideal Biosensor The output signal must be relevant to measurement enviornment The functional surface must be compatible with the transducer High specificity and sensitivity (low interference) Sufficient sensitivity and resolution Surface accuracy and repeatability Sufficient speed of response Sufficient dynamic range Intensivity to enviornmental interference or their effects must be compensated

17. Basic characteristics of Biosensor LINEARITY – linearity of the sensor should be high for the detection of high substrate concentration SENSITIVITY – Value of the electrode response per substrate concentration SELECTIVITY – Chemicals interference must be minimised for obtaining the correct result RESPONSE TIME – Time necessary for having 95% of the response

18. Typical Sensing Techniques Fluorescence DNA Microarray SPR (Surface Plasma Resistance) Impedance Spectroscopy SPM (Scanning Probe Microscopy) QCM (Quartz Crystal Microbalance) SERS (Surface Enhanced Raman Spectroscopy)

19. T ypes Calorimetric / Thermal Detection Biosensors Optical Biosensors Resonant Biosensors Piezoelectric Biosensors Ion Sensitive Biosensors Electrochemical Biosensors * Conductimetric Sensors * Amperometric Sensors * Potentiometric Sensors

20. Calorimetric / Thermal Detection Biosensors Uses Absorption / Production of heat Total heat produced / absorbed is α Molar Enthalpy / Total No. of molecules in the run Tem. Measured by Enzyme Thermistors Advantages No need of frequent recalibration Intensitive to the optical and electrochemical properties of the sample Uses Detection of : (1) Pesticides (2) Pathogenic bacteria

21. Ion Sensitive Biosensors Surface electrical potential changes when the ion and semiconductor interact Measures the change in potential Uses Detection of pH Electrochemical Biosensors Many chemical runs produce or consume ions or electrons causing some change in the electrical properties of the solution that can be sensed out and used as a measuring parameter Uses Detection of :- (1) hybridized DNA (2) DNA binding drugs (3) glucose concentration

22. Optical Biosensors Colorimetric for colour – Measure change in light adsorption Photometric for light intensity – Detects the photon input Resonant Biosensors An Acoustic Wave Transducer is coupled with bioelement Measures the change in Resonant Frequency Piezoelectric Biosensors Uses gold – To detect specific angle at which electron waves are emitted when the substance is exposed to laser light/ crystals like quartz, which vibrates under the influence of an electric field Change in frequency α Mass of absorbed material

23. Conductimetric Sensors Measures electrical conductance / resistance of the solution Measurement has low sensitivity Electrical voltage is generated using sinusoidal (ac) voltage, which helps in minimizing undesirable effects like : i ) Faradiac processes ii) Double layer charging iii) Concentration polarization Amperometric Biosensors High sensitivity Detects the electroactive species present in the biological test samples Measured parameter – current

24. Potentiometric Sensors Working principle – when voltage is applied to an electrode in solution a current flow occurs because of electrochemical reactions Measured parameter – oxidation / reduction potential of an electrochemical run

25. Applications Food analysis Study of biomolecules and their interaction Drug development Crime detection Medical diagnosis (both clinical and laboratory use) Enviornmental field monitoring Quality control Industrial process control Detection systems for biological warefare agents Manufacturing of pharmaceuticals and replacement organs