BIOSENSOR : BIOSENSOR By: Devender Arora What its mean? : What its mean? A Biosensor is an analytical device which convert a biological response into an electrical signal
>>Basic principle on which Biosensor Based<< Biosensors : Biosensors Combine a biological compound with a transducer
Que: What is a transducer?
Ans: Conventional enzyme electrodes use bulky electrochemical devices as transducers, such as the oxygen electrode and hydrogen electrode It consists of 3 parts: : 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 Why biosensor are important ? : Why biosensor are important ? They Play Important Role In..
1. Important tools in food safety, diagnostics, medical monitors, and detection systems for biological warfare agents.
2. important devices offering analytical simplicity both in and outside the analytical laboratory.
3. selective, rapid and sensitive instruments for determination of chemical and biochemical targets. Classification -1 : Classification -1 Types of Biological Recognition Name of the BIOSENSOR
Enzymes Enzyme electrode
DNA DNA sensor
Microbial cells Microbial sensor Classification-2 : Classification-2 Types of Transducers Measured Property
Electrical Surface conductivity
Mass sensitive Resonant frequency of piezocrytals
Thermal Heat of reaction
Heat of adsorption Basic Characteristics of a biosensor : Basic Characteristics of a biosensor 1. LINEARITY: Maximum linear value of the sensor
calibration curve. Linearity of the sensor must be high for the detection of high substrate concentration.
2. SENSITIVITY: The value of the electrode response per substrate concentration.
3. SELECTIVITY: Interference of chemicals must be
minimized for obtaining the correct result.
4. RESPONSE TIME: The necessary time for having 95% of the response. Uses of Biosensors : Uses of Biosensors 1.Environmental Monitoring
4.Medical Types of Biosensors : Types of Biosensors Calorimetric Biosensor
Piezo-electric Biosensor Piezo-Electric Biosensors : Piezo-Electric Biosensors Piezo-electric devices use gold to detect the specific angle at which electron waves are emitted when the substance is exposed to laser light or crystals, such as quartz, which vibrate under the influence of an electric field.
The change in frequency is proportional to the mass of absorbed material. Electrochemical Biosensors : Electrochemical Biosensors For applied current: Movement of e- in redox reactions detected when a potential is applied between two electrodes Potentiometric Biosensor : Potentiometric Biosensor For voltage: Change in distribution of charge is detected using ion-selective electrodes, such as pH-meters Optical Biosensors : Optical Biosensors Colorimetric for color
Measure change in light adsorption
Photometric for light intensity
Photon output for a luminescent or fluorescent process can be detected with photomultiplier tubes or photodiode systems. Calorimetric Biosensors : Calorimetric Biosensors If the enzyme catalyzed reaction is exothermic,
two thermistors may be used to
measure the difference in resistance
between reactant and product and, hence,
the analyte concentration. Electrochemical DNA Biosensor : Electrochemical DNA Biosensor Steps involved in electrochemical DNA hybridization biosensors:
Formation of the DNA recognition layer
Actual hybridization event
Transformation of the hybridization event into an electrical signal Present Applications of Biosensors : Present Applications of Biosensors 1. Medical Care (both clinical and laboratory use)
2. The determination of food quality
3. The detection of environmental pollutants
4. Industrial Process Control Slide 19: A successful biosensor must possess at least some of the following beneficial features:
The biocatalyst must be highly specific for the purpose of the analyses, be stable under normal storage conditions and, except in the case of colorimetric enzyme strips and dipsticks (see later), show good stability over a large number of assays (i.e. much greater than 100).
The reaction should be as independent of such physical parameters as stirring, pH and temperature as is manageable. This would allow the analysis of samples with minimal pre-treatment. If the reaction involves cofactors or coenzymes these should, preferably, also be co-immobilised with the enzyme
The response should be accurate, precise, reproducible and linear over the useful analytical range, without dilution or concentration. It should also be free from electrical noise.
If the biosensor is to be used for invasive monitoring in clinical situations, the probe must be tiny and biocompatible, having no toxic or antigenic effects. If it is to be used in fermenters it should be sterilisable. This is preferably performed by autoclaving but no biosensor enzymes can presently withstand such drastic wet-heat treatment. In either case, the biosensor should not be prone to fouling or proteolysis.
The complete biosensor should be cheap, small, portable and capable of being used by semi-skilled operators.
There should be a market for the biosensor. There is clearly little purpose developing a biosensor if other factors (e.g. government subsidies, the continued employment of skilled analysts, or poor customer perception) encourage the use of traditional methods and discourage the decentralisation of laboratory testing. Example of biosensors : Example of biosensors Pregnancy test
Detects the hCG protein in urine. Glucose monitoring device (for diabetes patients)
Monitors the glucose level in the blood. Example of biosensors : Example of biosensors Infectous disease biosensor from RBS