198
Bacterial Cellulose
of. a. microvascular. network. within. BNC. structures.. The. movement. of.
G. xylinus.at.the.nanoscale.can.be.controlled.by.electric.fields.to.create. .
custom. cellulose. networks. for. engineered. tissues. and. biomedical.
implants..This.is.the.first.attempt.to.control.a.bottom-up.biofabrication.
process.in.three.dimensions..The.manipulation.of.electrokinetic.forces.
acting.upon.a.bacterial.cell.can.produce.complex.cellulose.patterns.on.
the.nanoscale.not.achievable.in.static.culture..The.ability.to.control.the.
direction.of.fiber.orientation.could.be.readily.expanded.to.weave.structures.of.multiple.fiber.layers.by.changing.the.orientation.of.the.applied.
electric. field. for. each. layer.. Using. this. method,. these. structures. could.
be.tailored.to.have.desired.mechanical.properties.for.a.variety.of.applications,. including. tissue. engineering,. microelectromechanical. systems.
(MEMS),.textiles,.and.electronics.
Introduction
astating.diseases.of.our.time..Because.engineered.tissue.and.organ.replacements.can.be.developed.in.a.laboratory,.therapies.can.potentially.be.delivered.
on. a. large. scale. for. multiple. disease. states. with. dramatic. reductions. in.
waiting. times. for. patients.. The. concept. of. engineering. tissue. using. selective.cell.transplantation.has.been.applied.experimentally.and.clinically.for.a.
. variety.of.disorders,.including.the.successful.use.of.engineered.skin.for.burn.
dures.(Solchaga.et.al..1999),.and.engineered.bladder.tissue.for.bladder.reconstruction.(Atala.2002)..The.process.for.engineering.tissues.involves.in.vitro.
seeding.and.attachment.of.human.cells.onto.a.scaffold.(Temenoff.and.Mikos.
2000)..These.cells.then.proliferate,.migrate,.and.differentiate.within.the.scaffold. while. secreting. (or. resorbing). the. extracellular. matrix. components. of.
the.specific.tissue.type.of.interest..Therefore.the.choice.of.scaffold.material.is.
crucial.to.enable.the.cells.to.produce.tissues.and.organs.of.the.desired.shape,.
size,.and.mechanical.properties..Scaffolding.for.tissue.engineering.usually.
consists. of. polymers,. both. natural. and. synthetic.. Some. methods. of. forming.polymer.scaffolds.for.tissue.engineering.are.decellularization.of.animal.
. tissue.(Badylak.et.al..1989),.solvent.casting,.particulate.leaching,.gas.foaming.
of.polymers.(Nam.et.al..2000),.phase.separation.(Lo.et.al..1995),.and.solution.
casting.(Zhou.et.al..2005)..Electrospinning.is.another.popular.method.for.creating.fibrous.scaffolds.for.engineered.tissues.and.organs.(Stitzel.et.al..2006).
Currently.scaffold.fabrication.techniques.suffer.from.fundamental.manufacturing.limitations.that.have,.to.date,.prevented.their.clinical.translation..
Specifically,.there.is.a.distinct.lack.of.processes.capable.of.reproducibly.creating.structures.on.the.nano-,.micro-,.and.millimeter.scales.that.predictably.
promote.cell.growth.and.function.
Bacterial Cellulose
of. a. microvascular. network. within. BNC. structures.. The. movement. of.
G. xylinus.at.the.nanoscale.can.be.controlled.by.electric.fields.to.create. .
custom. cellulose. networks. for. engineered. tissues. and. biomedical.
implants..This.is.the.first.attempt.to.control.a.bottom-up.biofabrication.
process.in.three.dimensions..The.manipulation.of.electrokinetic.forces.
acting.upon.a.bacterial.cell.can.produce.complex.cellulose.patterns.on.
the.nanoscale.not.achievable.in.static.culture..The.ability.to.control.the.
direction.of.fiber.orientation.could.be.readily.expanded.to.weave.structures.of.multiple.fiber.layers.by.changing.the.orientation.of.the.applied.
electric. field. for. each. layer.. Using. this. method,. these. structures. could.
be.tailored.to.have.desired.mechanical.properties.for.a.variety.of.applications,. including. tissue. engineering,. microelectromechanical. systems.
(MEMS),.textiles,.and.electronics.
Introduction
astating.diseases.of.our.time..Because.engineered.tissue.and.organ.replacements.can.be.developed.in.a.laboratory,.therapies.can.potentially.be.delivered.
on. a. large. scale. for. multiple. disease. states. with. dramatic. reductions. in.
waiting. times. for. patients.. The. concept. of. engineering. tissue. using. selective.cell.transplantation.has.been.applied.experimentally.and.clinically.for.a.
. variety.of.disorders,.including.the.successful.use.of.engineered.skin.for.burn.
dures.(Solchaga.et.al..1999),.and.engineered.bladder.tissue.for.bladder.reconstruction.(Atala.2002)..The.process.for.engineering.tissues.involves.in.vitro.
seeding.and.attachment.of.human.cells.onto.a.scaffold.(Temenoff.and.Mikos.
2000)..These.cells.then.proliferate,.migrate,.and.differentiate.within.the.scaffold. while. secreting. (or. resorbing). the. extracellular. matrix. components. of.
the.specific.tissue.type.of.interest..Therefore.the.choice.of.scaffold.material.is.
crucial.to.enable.the.cells.to.produce.tissues.and.organs.of.the.desired.shape,.
size,.and.mechanical.properties..Scaffolding.for.tissue.engineering.usually.
consists. of. polymers,. both. natural. and. synthetic.. Some. methods. of. forming.polymer.scaffolds.for.tissue.engineering.are.decellularization.of.animal.
. tissue.(Badylak.et.al..1989),.solvent.casting,.particulate.leaching,.gas.foaming.
of.polymers.(Nam.et.al..2000),.phase.separation.(Lo.et.al..1995),.and.solution.
casting.(Zhou.et.al..2005)..Electrospinning.is.another.popular.method.for.creating.fibrous.scaffolds.for.engineered.tissues.and.organs.(Stitzel.et.al..2006).
Currently.scaffold.fabrication.techniques.suffer.from.fundamental.manufacturing.limitations.that.have,.to.date,.prevented.their.clinical.translation..
Specifically,.there.is.a.distinct.lack.of.processes.capable.of.reproducibly.creating.structures.on.the.nano-,.micro-,.and.millimeter.scales.that.predictably.
promote.cell.growth.and.function.