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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 E-field, 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/
shockwave.html
• 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/
chip/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.