eee 529 microsystems amperometric biosensors
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EEE 529 Microsystems Amperometric Biosensors
Agamyrat Agambayev 520112003
Contents:1. Introduction to Biosensors2. Definitions3. Amperometric Biosensors4. Generations of Amperometric Biosensors5. Performance factors6. Applications7. References
MULTIDISCIPLINARY NATURE OF BIOSENSOR:
INTRODUCTIONBIOSENSORS :Compact analytical devices that bring together the use of a biological, a biologically-derived or a biomimic element to recognize the analyte.
INTRODUCTIONBiosensor = biorecognation element + transducer.
Biorecognation elementa biomolecule that recognizes the target analyte Transducer converts the recognition event into a measurable signal
The uniqueness of a biosensor is that the two components areintegrated into one single sensor
INTRODUCTIONBiosensor = biorecognation element + transducer.
Biosensor = biorecognation element + transducer.
Transducer. A transducer should be capable of converting the biorecognition event into a measurable signal .Typically, this is done by measuring the change that occur in the bioreceptor reaction. For example, the enzyme glucose oxidase (used as a bioreceptor in a glucose biosensor) catalyzes the following reaction:Glucose + O2 --------> Gluconic acid + H2O2
To measure the glucose concentration, 3 different transducers can be used: An oxygen sensor that measures oxygen concentration A pH sensor that measures the acid (gluconic acid) production A peroxide sensor that measures H2O2 concentration. Note: An oxygen sensor is a transducer that converts oxygen concentration into electrical current. A pH sensor is a transducer that converts pH change into voltage change. A peroxidase sensor is a transducer that converts peroxidase concentration into an electrical current.
The choice of the biological recognition element is the crucial decision that is taken when developing a novel biosensor design.
It is important to define criteria for, for example, a suitable redox enzyme for a specific biosensor.
Most importantly, the enzyme needs to selectively react with the analyte of interest.
The redox potential of the primary redox center needs to be within a suitable potential window (usually between − 0.6 and 0.9 V vs. Ag/AgCl).
The enzyme needs to be stable under the operation and storage conditions of the biosensor and should provide a reasonable long - term stability.
Advantages and Disadvantages of using Enzymes in sensors
ADVANTAGES DISADVANTAGES
• Highly selective
• Catalytically active
improve sensitivity
• Fairly fast-acting
• One of the most known
biological components
• Expensive
• A loss activity when
immobilized on a
transducer
• Tending to lose activity
after a relatively short
period time
Considerations for biosensor development
Selection of a suitable biorecognation molecule
Selection of a suitable immobilization method
Selection of a suitable transducer
Designing of biosensor considering measurement range, linearity, and minimization of interference
Packaging of biosensor
Biosensors are classified according to the parameter thatis measured by the physicochemical transducer of the biological event as: Optical, Electrochemical ---- > Amperometric Acoustic, Thermal.
Amperometric Biosensors: the oldest ones, which have led to the higher number of ready to- use devices, are based on the monitoring of electron-transfer processes
Redox (reduction-oxidation) reactions include all chemical reactions in which atoms have their oxidation state changed.
Amperometric Biosensors produce a current proportional to the concentration of the substance to be detected.
The most common amperometric biosensors use the Clark Oxygen electrode.
In the glucose Amperometric Biosensor, the Clark Oxygen electrode is separated from glucose by a membrane, that is permeable to oxygen. A biocatalyst Glucose Oxidase(GOD) is housed between this membrane and another membrane that separates it from the glucose. This membrane that separates GOD and glucose is permeable to both Oxygen and Glucose.
In effect, the enzyme GOD is immobilized between two membranes, the top being permeable only to oxygen and the bottom to both Oxygen and Glucose.
The Glucose that enters the membrane is Oxidised in presence of the enzyme GOD, to produce Glucuronic acid and Hydrogen Peroxide.
glucose + O2 – > glucuronic acid + H2O2
Hence the concentration of oxygen decreases as it moves up through the membranes to reach the cathode. This decrease in Oxygen concentration is reflected as a decrease in current between the electrodes.
Alternatively, the decrease in the concentration of Hydrogen Peroxide can also be used to find the concentration of glucose, by changing the voltage applied between the electrodes to +0.68 V relative to the Ag/AgCl electrode causing the reactions:
Pt anode H2O2 -- > O2 + 2H+ + 2e-
Ag cathode 2AgCl + 2e- -- > 2Ag0 + 2Cl-
1st generation: the normal product of the reaction diffuses to the transducer and causes electrical response
1st generation: the normal product of the reaction diffuses to the transducer and causes electrical response
1st generation: the normal product of the reaction diffuses to the transducer and causes electrical response
1st generation: the normal product of the reaction diffuses to the transducer and causes electrical response
2nd generation: involves specific mediators between reaction and transducer to generate improved response
2nd generation: involves specific mediators between reaction and transducer to generate improved response
2nd generation: involves specific mediators between reaction and transducer to generate improved response
2nd generation: involves specific mediators between reaction and transducer to generate improved response
2nd generation: involves specific mediators between reaction and transducer to generate improved response
2nd generation: involves specific mediators between reaction and transducer to generate improved response
3rd generation: reaction itself causes the response
3rd generation: reaction itself causes the response
AMPEROMETRIC BIOSENSORS
Substrate Bioreceptor Product detected
Range, mM
choline choline oxidase H2O2 500ethanol alcohol oxidase H2O2 0 - 10formaldehyde f. dehydrogenase NADH 10-3glucose glucose oxidase H2O2, O2 0-7 g/Lglutamine glutamine oxidase H2O2 0-25glycerol g. dehydrogenase NADH, O2
hypoxanthine x. oxidase H2O2 4-180lactate lactate oxidase H2O2 1-40
oligosaccharidesglucoamylase, glucose oxidase H2O2 0.1-2.5
phenol polyphenol oxidasequinone
PERFORMANCE FACTORS
Selectivity Sensitivity Accuracy Response time Recovery time Lifetime
PERFORMANCE FACTORS
References A.G. Elie,Principles of Potentiometric and Amperometric
Biosensors,University of Virginia,(2002) P.V. Climent, M.L.M.Serralheiro, and M.J.F. Rebelo, Pure and Applied
Chemistry 73, pp.1993-1999, 2001 http://www.lsbu.ac.uk.html http://www.gatewaycoalition.org/files/Hidden/sensr/tocsenf.htm http://techramble.wordpress.com/2009/08/03/amperometric-biosensors/ http://www.lbb.ethz.ch/Education/Biosensors/2011FSlesson4TZ
Thank You
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