BioSensors

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BioSensors

• Yang Yang
• 9/28/2004

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Outlines
BioMEMS Enzyme-coated carbon nanotubes Microcant
ilever biosensor with environmentally responsive
hydrogel Cantilever array based nanotechnology
olfactory sensors Conclusion
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BioMEMS
Inetegration of life science/biomedical Discipline
s with micro- and nano- Scale systems
and materials.
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BioMEMS
Materials used for fabrication
Biosensors
Biosensors are analytical devices that combine a
biologically sensitive Element with a physical or
chemical transducer to selectively and
quan- Titatively detect the presence of specific
compounds in a given external environment.
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BioMEMS
BiosensorMechanical detection
Mass mode cantilever sensor
Stress mode cantilever sensor
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BioMEMS
Biosensor-- Electrical detection
Potentio, measures the potential at an electrode
in reference to another
Ampero, monitors formation of H in a redox
process
Conducto, measures the changes in Electrical
impedance between 2 electrodes.
Both ampero- and potentio- need reference
electrodes, which makes the fabrication difficult.
Conducto- does not.
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BioMEMS
Biosensor-- Optical detection
Based on fluorescence or chemiluminescence.
Fluorescence- fluorescent markers emits light
at specific wavelengths,
thus any change in
optical signal indicates
a binding reaction. Chemiluminescence- light is
generated by the
release of energy as a result of a
chemical reaction.
Cited paper
R. Bashir, BioMEMS state-of-the-art in
detection, opportunities and prospects, Advanced
drug delivery reviews, 56 (2004) 1565-1586
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Enzyme-Coated Carbon Nanotubes
Manufacturing method
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Enzyme-Coated Carbon Nanotubes
Effects of GOx immobilization

• After immobilization
• AFM height 5 nm ? 8 nm
• 1 GOx molecule per 12 nm
• Conductance of SWNT decreases
• significantly (black ? cyan)

4. pH dependent
bare SWNT
50 GOx molecules on SWNT
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Enzyme-Coated Carbon Nanotubes
Effects of GOx immobilization
Pros
5. Glucose sensitive.

• Very sensitive to testing entities.
• Excellent nanosize pH sensor
• can measure pH as low as 0.1
• Enzyme detector
• can measure the enzymatic
• activity of a single redox enzyme.

Cited paper
K. Besteman, et al, Enzyme-coated Carbon
nanotubes as single- Molecule biosensors, vol. 3,
no. 6 ,727-730, 2003
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Microcantilever Biosensor withEnvironmentally
Responsive Hydrogel
Method of fabrication
Released cantilever
Oxide layer
Silicon layer
Silicon-On Insulator (SOI) wafer
Buried silicon layer
Etch using photoresist mask
Soaked in organosilane gaining bonding
between polymers and cantilever
Soaked in hydro- Fluoric acid to etch Off all
oxide
Etch out 3 layers at selected locations
Dry etch out oxide on substrate
Grown oxide
Use tetramethylammonium hydroxide to etch the
silicon substrate and to form the Cantilever/oxid
e composite
Precise photo-etching to form coated cantilever
Cantilever/oxide combo
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Microcantilever Biosensor withEnvironmentally
Responsive Hydrogel
Testing results
Hydrogel film capable of Sensing the change in
pH Sensitivity of pH is Per 1 nm bending
Increasing pH path
Decreasing pH path
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Microcantilever Biosensor withEnvironmentally
Responsive Hydrogel
Pros

• Very sensitive to changes in pH
• Response features can be controlled
• by modifying swelling properties of the
• coating material, by changing the dimension
• of cantilever, etc
• Can be testing sample specific by bonding
• other environmentally responsive hydrogels.

Cited paper
J.Z. Hilt, et al, Ultrasensitive biomems sensors
based on microcantilevers Patterned with
environmentally responsive hydrogels, Biomedical
microdevice 53, 177-184, 2003
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Cantilever Array Based Nanotechnology Olfactory
Sensors (NOSE)
Cantilever sensors array and polymer coatings
Cantilever length
thickness
width
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Cantilever Array Based Nanotechnology Olfactory
Sensors (NOSE)
Schematic setup
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Cantilever Array Based Nanotechnology Olfactory
Sensors (NOSE)
Data acquisition
Signal magnitude for each one of the 8
cantilevers at 5 acquisition Instants with the
injection of etha-nol
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Cantilever Array Based Nanotechnology Olfactory
Sensors (NOSE)
Data processing (Principal Compo- nents Analysis)
PCA is a statistical method that rotates a data
set such that the max. variability is visible and
the Most important gradients are Identifiedmore.
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Cantilever Array Based Nanotechnology Olfactory
Sensors (NOSE)
Differential measurement in liquids
Noises occur in liquid envir. measurement changes
in pH Ion concentration temperature and
etc.
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Cantilever Array Based Nanotechnology Olfactory
Sensors (NOSE)
Pros and Cons
Reference sensors can be used for differential
measurements It can be used in various
media High sensitivity over a wide range of
operating temperatures It can be integrated
into other systems Relatively long response
time.
Cited paper
M.K. Baller, et al, A cantilever array-based
artificial nose, Ultramicroscopy, 82 (2000) 1-9
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Conclusion

• Biosensors are very small, very sensitive and
• can be transplanted to human body
• Dramatically improve efficiency in drug discovery
  research
• Multidisciplinary