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Biosensors for Environmental Monitoring

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Fluorescence Illuminates Chemical Warfare Agents. What is a Biosensor? ... This new idea stems from the urgency to detect chemical warfare agents very quickly. ... – PowerPoint PPT presentation

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Title: Biosensors for Environmental Monitoring


1
Biosensors for Environmental Monitoring
  • Fluorescence Illuminates Chemical Warfare Agents

2
What is a Biosensor?
  • A device that uses specific biochemical reactions
    mediated by isolated enzymes, immunosystems,
    tissues, organelles or whole cells to detect
    chemical compounds usually by electrical, thermal
    or optical signals.
  • It is the common name of sensors even though
    enzymes may not be used at all.
  • Uses for biosensors continues to grow.

3
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4
Types of Biosensors
  • Calorimetric changes in heat used to determine
    concentrations
  • Potentiometric - pH-meter used for measuring
    reactions generating or absorbing hydrogen ions
  • Amperometric - function by the production of a
    current when a potential is applied between two
    electrodes
  • Piezo-electric measures quartz vibrations under
    the influence of an electric field
  • Immunosensors - to detect and amplify an
    antigen-antibody reaction
  • Optical - involve determining changes in light
    absorption between the reactants and products of
    a reaction, or measuring the light output by a
    luminescent process

5
Functional Component
  • The transducer makes use of the specific changes
    that accompany reactions in order to produce an
    electrical signal.

6
Transducers can produce signals from
  • the heat of the reaction (calorimetric
    biosensors)
  • changes in the distribution of charges causing an
    electrical potential to be produced
    (potentiometric biosensors),
  • movement of electrons produced in a redox
    reaction (amperometric biosensors),
  • light output during the reaction or a light
    absorbance difference between the reactants and
    products (optical biosensors)
  • effects due to the mass of the reactants or
    products (piezo-electric biosensors)

7
Makings of an ideal biosensor.
  • must be highly specific for the purpose of the
    analyses, be stable under normal storage
    conditions and show good stability over a large
    number of assays
  • 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.
  • The response should be accurate, precise and
    reproducible
  • If the biosensor is to be used for invasive
    monitoring in clinical situations, the probe must
    be biocompatible
  • The complete biosensor should be dummy proof
  • There should be a market for the biosensor.

8
Plans for a new optical sensor
  • Again, optical biosensors read light output from
    luminescence or absorption differences. This
    sensor will utilize luminescence.
  • This new idea stems from the urgency to detect
    chemical warfare agents very quickly.

9
The Coumarine Oximate detector is
  • replacing calorimetric devices for detection.
  • replacing alcohols in previous mechanisms.
  • currently is stand alone
  • not yet integrated into a working sensor
  • still in the process of becoming a practical
    application

10
Coumarin benzene pyran ketone benzopyrone
11
Oximes
12
Synthesis of Coumarin Oximate
13
  • A coumarin aldehyde is converted to a coumarin
    oxime.
  • The oxime loses a hydrogen when base is added to
    become an oximate.
  • Special base is used to avoid interference with
    the nerve gas.

14
Mechanism
15
Phosphoryl Fluorides
16
What makes it glow?
17
Chemically Initiated ElectronExchange
Luminescence
  • Hydrogen peroxide reacts with the oxalate to give
    peroxalate.
  • Dioxitane dione considerd to be the key
    intermediate step in producing chemiluminescence
  • The electron transfer drives the chemliminescence

18
Reaction of Coumarin Oximate with no DFP Present
19
  • In this case, no CW agent or model yields no
    light.
  • What ends up happening is the oximate binds to
    the oxalate.
  • No reaction with hydrogen peroxide can take
    place.
  • No chemiluminescence

20
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21
  • Here we see that DFP rather than the base
    attaches to the oximate.
  • The oxalate is free to react with hydrogen
    peroxide.
  • Chemiluminescence is observed.

22
  • What is not apparent is how exactly the reactants
    can get back to their starting point.
  • There needs to be a way to hold back the oxalate
    from reacting with hydrogen peroxide.

23
Recap
  • Biosensors are sophisticated tools for detection
    and monitoring.
  • New technology is allowing more specificity and
    quicker, more accurate readings.
  • New methods and uses for biosensors continues to
    grow with increasing demand.

24
References
  • Martin Chaplin and Christopher Bucke, Enzyme
    Technology, (Cambridge University Press, 1990).
  • Himali S. Hewage,a Karl J. Wallaceb and Eric V.
    Anslyn, Novel chemiluminescent detection of
    chemical warfare simulant, Received (in
    Cambridge, UK) 2nd May 2007, Accepted 26th July
    2007First published as an Advance Article on the
    web 8th August 2007 DOI10.1039/b706624d.
  • Karl J. Wallace,a Ruth I. Fagbemi,a Frantz J.
    Folmer-Andersen,a Jeroni Morey,b Vincent M.
    Lyntha and Eric V. Anslyn, Detection of chemical
    warfare simulants by phosphorylation of a
    coumarin oximate ,Received (in Cambridge, UK)
    11th July 2006, Accepted 11th August 2006 First
    published as an Advance Article on the web 1st
    September 2006 DOI 10.1039/b609861d.
  • IUPAC Compendium of Chemical Terminology 1992,
    64, 14 2nd Edition (1997).
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