Biomedical Engineering Reference
In-Depth Information
mimicking.the.ECM,.with.high.surface.area,.high.aspect.ratio.pores,.high.porosity,.small.
pore. size,. and. low. density.. This. scaffold. manufacturing. technique. had. introduced. new.
processing. options. for. the. regeneration. of. many. tissues,. such. as. vascular. (Boland. et. al..
2004),.neural.(Li.et.al..2006),.and.bone.(Catledge.et.al..2007).
For.a.basic.electrospinning.experiment,.several.elements.are.required:.(1).the.polymer.
solution.or.polymer.melt.delivery.system,.mostly.consisting.of.a.syringe.or.capillary.tube.
together. with. a. syringe. pump. for. the. delivery. of. continuous. and. calibrated. amounts. of.
polymer;.(2).the.power.source.providing.the.electron.potential.desired.for.polymer.jet.from.
pendent. droplet;. and. (3). the. grounded. target. from. a. distance. collecting. spun. scaffolds..
Due.to.the.nature.of.the.electrospinning.process,.randomly.oriented.ibers.are.produced..
Recent.efforts.have.focused.on.electrospinning.aligned.ibers..By.varying.the.shape,.size,.
rotation,.and.distance.between.the.target.and.source,.it.is.possible.to.create.a.wide.range.
of.spun.material.ranging.from.random.nanoibers.to.highly.aligned.scaffolds,.as.well.as.to.
control.the.diameter.of.the.ibers.
Both. natural. and. synthetic. materials. have. been. electrospun. into. random. and. aligned.
meshes. mimicking. collagen,. gelatin,. and. chitosan.. Poly(glycolic. acid). (PGA). was. one. of.
the. irst. polymer. solutions. used. in. electrospinning;. 0.2-1.2.μm. PGA. ibers. were. created.
by. dissolving. PGA. in. solvent. (Boland. 2001).. Scaffolds. created. using. PLA,. which. is. very.
similar. to. PGA,. exhibited. differences. in. degradation. and. mechanical. properties. (Stitzel.
et. al.. 2001).. This. led. to. the. idea. of. electrospinning. a. mixture. of. PGA. and. PLA. (PLGA).
in. different. concentrations. to. create. intermediate. scaffolds. with. tunable. degradation.
and. mechanical. properties. for. tissue. engineering. (Katti. et. al.. 2004,. Xin. et. al.. 2007)..
Electrospun. polydioxanone. was. also. explored. for. its. lexibility. comparing. to. that. of.
PLGA..As.electrospun.PCL.showed.much.slower.degradation.rate.(1-2.years),.it.had.been.
considered.another.class.of.biodegradable.polymer.that.is.suitable.for.tissue.engineering.
(Reneker.2002)..Several.natural.polymers.have.also.been.explored,.such.as.collagen.type.
I,.II,.III,.and.silk.ibroin.(Bhattarai.et.al..2005,.2006,.Hofmann.et.al..2006a,.Bettinger.et.al..
2007),. for. their. biocompatibility.. In. addition. to. polymer. solutions,. there. are. many. other.
sample. options. for. electrospinning. suitable. scaffolds,. for. example,. polymer-polymer.
blends,.polymer-ceramic.composites,.and.polymer.melts.
With.the.superior.ECM-mimicking.capabilities.in.both.topography.and.chemistry,.many.
nanotopographically. deined. scaffolds. are. being. used. in. tissue. engineering. applications.
(Pham.et.al..2006)..The.tunable.mechanical.properties.of.electrospun.scaffolds.enable.the.cre-
ation.of.scaffolds.suitable.for.numerous.physiological.targets,.ranging.from.elastic.to.plastic.
(Kwon.et.al..2005)..The.oriented.ibers.are.particularly.useful.for.applications.requiring.soft.
mechanical.properties,.for.instance,.in.dermal,.neural,.and.cartilage.tissue.regeneration.
22.3 Nanoscale Features for Tissue Regeneration
Nanoscale.topography.has.been.shown.to.be.an.important.signaling.interface.with.mam-
malian.cells.for.the.control.of.cell.function..ECM.naturally.presents.nanotopographic.struc-
tures.with.mechanotransductive.cues.that.dominate.local.cell.migration,.cell.polarization,.
and.other.functions..Synthetically.nanofabricated.topographical.surfaces.have.been.shown.
to.inluence.cell.morphology,.alignment,.adhesion,.migration,.proliferation,.and.cytoskel-
eton.organization.in.many.speciic.tissues,.such.as.bone.(Zhang.et.al..2009),.liver.(Bettinger.
et. al.. 2009a),. and. retina. (Neeley. et. al.. 2008).. The. in. vitro. synthetic. cell-nanotopography.
