Tutorial 10 Derek Wright Wednesday, March 30 th, 2005.

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.