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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 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 • • • • 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.
