OPTICAL BIOSENSORS
• A. Erol Fazlıoğlu
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.
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.
Definition and Its Applications-1
• Biosensors are analytical devices that can
detect chemical or biological species or a
microorganism.
Applications:
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Clinical diagnostics
Drug development
Environmental monitoring (air, water, and soil)
Food quality control
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.
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.
Advantages of Optical Biosensors
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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
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
Antibody-antigen
Optical Transduction
Fluorescence Sensing
• Direct Sensing
• Indirect Sensing.
Optical Geometries of Biosensing
Immobilization
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Physical Methods
Ionic Binding
Physical Entrapment
Chemical Immobilization
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.
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.
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).
Interferometric Biosensors
• Utilizes interference between the light from a
waveguiding channel with a sensing layer on its
surface, and that from a reference channel.
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.
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
Future Directions
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Multianalyte Detection
New Biorecognition Molecules
Fluidics
In Vivo Sensors
Chemical Identification Biosensors
Data Processing, Pattern Recognition,
and Automation
Thanks for your attention!
• Any questions?
• A. Erol Fazlıoğlu