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lecture17 - 3.051J/20.340J Lecture 17 Biosensors 1. What...

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1 3.051J/20.340J Lecture 17 Biosensors 1. What are biosensors? The term is used in the literature in many ways. Some definitions: a) A device used to measure biologically-derived signals b) A device that “senses” using “biomimetic” (imitative of life) strategies ex.,“artificial nose” c) A device that detects the presence of biomolecules We will adopt a recent IUPAC definition: “A self-contained integrated device which [sic] is capable of providing specific quantitative or semi-quantitative analytical information using a biological recognition element which is in direct spatial contact with a transducer element.” 2. Uses of biosensors Quality assurance in agriculture, food and pharmaceutical industries ex. E. Coli, Salmonella Monitoring environmental pollutants & biological warfare agents ex., Bacillus anthracis (anthrax) spores Medical diagnostics ex., glucose Biological assays ex., DNA microarrays
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2 3.051J/20.340J 3. Classes of biosensors A) Catalytic biosensors : kinetic devices that measure steady-state concentration of a transducer-detectable species formed/lost due to a biocatalytic reaction Monitored quantities: i) rate of product formation ii) disappearance of a reactant iii) inhibition of a reaction Biocatalysts used: i) enzymes ii) microorganisms ii) organelles iv) tissue samples B) Affinity biosensors : devices in which receptor molecules bind analyte molecules “irreversibly”, causing a physicochemical change that is detected by a transducer Receptor molecules: i) antibodies ii) nucleic acids iii) hormone receptors Biosensors are most often used to detect molecules of biological origin , based on specific interactions.
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3 3.051J/20.340J Transducer biological element Electrolyte Analyte (ex., blood) Signal (1) (2) 4. Biosensor Components Immobilized (electrochemical) (chemical target) External medium Semipermeable membranes Analyte: chemical/biological target Semipermeable Membrane (1): allows preferential passage of analyte (limits fouling) Detection Element (Biological): provides specific recognition/detection of analyte Semipermeable Membrane (2): (some designs) preferential passage of by- product of recognition event Electrolyte: (electrochemical-based) ion conduction medium between electrodes Transducer: converts detection event into a measurable signal
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3.051J/20.340J 4 A) Detection Elements 1) Catalysis Strategies : enzymes most common ex., glucose oxidase, urease (catalyzes urea hydrolysis), alcohol oxidase, etc. Commercial Example:
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This note was uploaded on 11/11/2011 for the course BIO 2.797j taught by Professor Matthewlang during the Fall '06 term at MIT.

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lecture17 - 3.051J/20.340J Lecture 17 Biosensors 1. What...

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