OPTICAL BIOSENSORS

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OPTICAL BIOSENSORS

• A. Erol Fazlioglu

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Idea Behind Biosensors

• Medical Diagnostics
• Chemical and bioterrorism threat.
• Health danger posed by new strands of microbial
  organisms and spread of infectious diseases.
• Optical biosensors utilize optical techniques to
  detect and identify chemical or biological
  species.

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Two Important Components of Biosensing

• (i) a biorecognition element to detect chemical
  or biological species
• (ii) a transduction mechanism which converts the
  physical or chemical response of biorecognition
  into an optical signal.

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Definition and Its Applications-1

• Biosensors are analytical devices that can detect
  chemical or biological species or a
  microorganism.
• Applications
• Clinical diagnostics
• Drug development
• Environmental monitoring (air, water, and soil)
• Food quality control

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Definition and Its Applications-2

• A biosensor utilizes a biological recognition
  element that senses the presence of an analyte
  (the specie to be detected) and creates a
  physical or chemical response that is converted
  by a transducer to a signal.

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Main Components Of An Optical Biosensor

• (i) a light source
• (ii) an optical transmission medium (fiber,
  waveguide, etc.)
• (iii) immobilized biological recognition element
  (enzymes, antibodies or microbes)
• (iv) optical probes (such as a fluorescent
  marker) for transduction,
• (v) an optical detection system.

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Advantages of Optical Biosensors

• Selectivity and specificity
• Remote sensing
• Isolation from electromagnetic interference
• Fast, real-time measurements 
• Multiple channels/multiparameters detection
• Compact design
• Minimally invasive for in vivo measurements
• Choice of optical components for biocompatibility
• Detailed chemical information on analytes

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Biorecognition

• The biorecognition elements are biologies such as
  enzymes, antibodies, and even biological cells
  and microorganisms that selectively recognize an
  analyte.
• Some of the molecular bioreceptors used for
  biorecognition
• Enzymes
• Antibodies
• Lectins
• Neuroreceptors
• DNA/PNA

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Antibody-antigen
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Optical Transduction
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Fluorescence Sensing

• Direct Sensing
• Indirect Sensing.

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Optical Geometries of Biosensing
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Immobilization

• Physical Methods
• Ionic Binding
• Physical Entrapment
• Chemical Immobilization

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Fiber-optic Biosensors
Fiber-optic biosensors are widely used because
of their convenient geometry. for example,
longer interaction length and compatibility with
instruments used for in vivo biosensing.
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Planar Waveguide Biosensors

• Planar waveguides are media in which the
  propagation of an optical waveguide is confined
  in a dimension comparable to the wavelength of
  light.

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Evanescent Wave Biosensors

• These sensors rely on the light that is not
  confined within the waveguide itself, but
  penetrates into the surrounding medium of lower
  refractive index (cladding or air or into a
  surface immobilized biorecognition element) and
  thus senses the chemical environment on the
  surface of the waveguide (or fiber).

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Interferometric Biosensors

• Utilizes interference between the light from a
  waveguiding channel with a sensing layer on its
  surface, and that from a reference channel.

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Surface Plasmon Resonance Biosensors

• It is an extension of evanescent wave sensing,
  except that a planar waveguide is replaced by a
  metal-dielectric interface.
• Surface plasmons are electromagnetic waves that
  propagate along the interface between a metal and
  a dielectric material such as organic films.

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Some Recent Novel Sensing Methods

• Photonic Crystals Sensors
• Optical Sensor Array and Integrated Light Source
• Hybrid Transduction Biosensors
• Time Domain Sensing
• Surface-Enhanced Raman Sensors

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Future Directions

• Multianalyte Detection
• New Biorecognition Molecules
• Fluidics
• In Vivo Sensors
• Chemical Identification Biosensors
• Data Processing, Pattern Recognition, and
  Automation

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Thanks for your attention!

• Any questions?
• A. Erol Fazlioglu