Transcript Tutorial 10 (PowerPoint)

Tutorial 10
Derek Wright
Wednesday, March 30th, 2005
Nano-BioSystems
• Neuro-Electronic Interfacing
• Biomaterials
• DNA Microarrays
Neuro-Electronic Interfaces
• Focuses on interfacing between neurons
and electronic circuits
– Circuits use electrons and holes
– Neurons use ions in fluid
• Circuits have high carrier mobility relative
to neurons
• Both use electricity, but differently
Neurons
• Typically 20 m in diameter
• Surrounded by an electrically insulating
membrane
– Lipid = fat
• Ionic current can flow through the
membrane using special proteins
Neurons
Neuron-Chip Interfaces
• a) Neuron potential acts as a gate
voltage in a FET
• b) Voltage of the silicon induces Efield, which opens up ion channels
• c) Current through cell membrane
creates a potential between the cell
and the chip, again acting as a gate
voltage in a FET
• d) Voltage of the silicon induces
potential between the cell and the
chip, which opens up ion channels
Neuron Immobilization
• When neurons are placed on a chip they
grow connections to surrounding neurons
– Like ropes tying neurons together
• These connections pull neurons together
• The neurons move away from where they
were placed
• Pegs can be used to hold the neuron in
place
– Like a fence
Neuron Immobilization
Biomaterials
• Biological materials can be considered
nanotechnology
– We can use them to engineer new things!
– http://www.pbs.org/wgbh/aso/tryit/dna/shockw
ave.html
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Amino Acid: 0.6 nm
Polypeptide: 4 – 50 nm
Proteins: Made up of polypeptides
DNA is the ultimate nanotechnology
DNA Microarrays
• DNA is double stranded
• It can be split into single strands
• If two single strands meet and are
matching, they will bind
• A “gene chip” uses an array of different
single stranded DNA segments fastened in
a grid
DNA Microarrays
• A solution containing unknown DNA fragments is
“tagged” with fluorescent molecules
• The solution is poured over the gene chip
• Any matching pairs will bind
• The chip is illuminated with UV light
• The fluorescent molecules illuminate, indicating
their presence
• http://www.bio.davidson.edu/courses/genomics/c
hip/chip.html
DNA Microarrays
• The hard part is making the array with
single stranded genes
• How do you make so many different gene
segments and attach them to specific
locations?
• Many methods developed:
– Lithography
– Ink jet printing
– Direct writing
Thank You!
• This presentation will be available on the
web.