Biomedical Engineering Reference
In-Depth Information
the.origami.with.controlled.orientation.(e.g.,.lengthwise.vs..widthwise)..By.placing.these.
adhesive.stripes.along.the.two.lat.surfaces.of.a.rectangular.DNA.origami,.a.carbon.nano-
tube.crossbar.was.self-assembled.(Maune.et.al..2009)..After.connecting.leads.to.the.carbon.
nanotubes.via.electron.beam.lithography,.measurements.on.the.crossbar.showed.it.was.a.
junction.between.a.metallic.and.a.semiconducting.tube.
1.7 Conclusions and Perspectives
It. is. reasonable. to. wonder. whether. other. biopolymers. could. be. used. to. construct.
nanostructures.using.design.rules.similar.to.those.for.DNA.origami.or.tile.arrays..Some.
structures. have. been. made. using. RNA,. but. in. these. cases,. the. RNA. oligos. are. designed.
to. have. stable. 3D-folded. structures. that. in. turn. assemble. into. larger. nanostructures. via.
hydrogen.bonding.or.hydrophobic.interactions.(Chworos.et.al..2004,.Jaeger.and.Chworos.
2006)..This.design.strategy.is.similar.to.that.used.for.de.novo.protein.design.(Sasaki.and.
Lieberman.1996)..Because.these.design.principles.are.less.general.than.for.DNA.tiles.and.
origami,. most. researchers. do. not. use. RNA. or. proteins. as. the. main. structural. fabric. for.
nanostructures,.although.RNA.oligos.may.be.added.to.DNA.nanostructures.as.a.binding.
probe.or.for.catalytic.functionality..Likewise,.peptide.nucleic.acids.have.not.been.explored.
as. structural. materials,. probably. due. to. their. expense. relative. to. DNA. oligos.. If. the.
availability.of.these.biomaterials.improves,.this.could.be.a.new.opportunity.for.designing.
functional.nanostructures.
DNA. nanostructures. have. unprecedented. promise. in. three. areas:. rational. design.
of. heterogeneous. structures,. physical. and. chemical. reconigurability,. and. ability. to.
recruit. and. template. non-DNA. components. in. precise. locations. (Pinheiro. et. al.. 2011)..
Challenges. in. structure. design. include. improving. the. yields. and. folding. kinetics. of.
larger. 3D. structures. and. developing. structures. suitable. as. intermediaries. between.
optical.lithographic.patterns.and.sub-10.nm.patterning..Reconiguration.is.an.intriguing.
development,. which. is. bound. to. change. how. we. think. about. nanorobotics,. but. many.
of. the. current. methods. to. reconigure. DNA. nanostructures. (such. as. strand. invasion).
are. very. slow. (hour. timescale).. It. would. be. of. great. interest. to. extend. the. chemical.
and. physical. cues. for. reconiguration. and. to. use. those. cues. to. elicit. changes. in. the.
shape. and. function. of. nanostructures;. for. example,. developing. a. “walker”. that. can.
roll.or.fold-up.another.DNA.nanostructure..There.is.plenty.of.room.for.expanding.the.
materials. palette. for. non-DNA. components. to. attach. to. DNA. origami,. which. could.
extend. to. the. synthesis. of. structures. that. integrate. “hard”. materials. or. polymers. and.
DNA.nanostructures.
The.interface.between.DNA.nanostructures.and.cells.is.a.topic.of.growing.importance..
DNA. nanostructures. are. already. the. size. of. cell. organelles. (ribosome.∼40.nm. diameter),.
and. they. offer. the. ability. to. bridge. between. molecules. and. larger. biological. structures..
For.example,.a.gated.nanopore.that.could.insert.itself.into.the.cell.membrane.of.targeted.
cells. would. have. both. research. and. biomedical. applications,. as. would. a. nanostructure.
capable. of. recognizing. and. destroying. speciic. virus. particles.. The. stability. of. DNA.
nanostructures.in.various.biological.environments.and.their.interactions.with.the.immune.
systems.of.targeted.organisms.are,.therefore,.of.great.importance.for.future.applications.
in.nanomedicine.
