Biomedical Engineering Reference
In-Depth Information
8.1.3 Design Considerations
The. basic. tenets. of. substrate. design. include. biocompatibility. and. adequate. mechanical.
strength,.which.are.predominantly.relected.in.the.choice.of.material..For.biomimetic.sur-
faces.to.successfully.orchestrate.cell.behavior.akin.to.that.in.vivo,.this.requires.appropriate.
selection. of. physical. and. chemical. cues.. Different. cell. types. exhibit. varied. responses. to.
certain.topographical.structures.and.surface-functionalized.molecules..For.tissue.regen-
eration.endeavors,.the.designed.scaffold.should.be.representative.of.the.ECM.composition.
that.correlates.with.the.physiological.region.of.interest.
8.2 Nanofabrication Strategies
Nanotopographical. features. can. arise. spontaneously. through. a. plethora. of. surface. pro-
cessing.techniques..These.structures.tend.to.be.porous.or.ibrillar.in.nature..On.the.other.
hand,.other.approaches.involve.precise.nanopatterning.at.speciic.locations.on.a.substrate..
This. implementation. of. design. manifests. either. structurally. or. chemically.. The. former.
alters.the.physical.landscape.via.surface.deposition.of.material.or.etching.the.surface.itself;.
the. latter. relies. on. substrate-immobilized. bioactive. particles. to. invoke. different. cellular.
responses.(Anselme.et.al..2010)..The.following.subsections.provide.an.overview.of.popular.
techniques.and.highlight.select.key.indings.from.current.scientiic.literature.
8.2.1 unordered Topography
8.2.1.1 Electrospinning
Electrospinning.generates.ibrous.scaffold.architectures.with.resolution.to.the.nanoscale.
level.(Figure.8.2a)..This.technique.utilizes.a.polymer.solution.(or.polymer.melt).suspended.
within. a. capillary. (Frenot. and. Chronakis. 2003).. When. placed. in. a. high. electrical. ield,.
the.electrostatic.forces.overcome.the.inherent.surface.tension.of.the.polymer.luid.in.the.
capillary.needle..Subsequent.elongation.and.thinning.of.the.solution.produces.nanoibers.
through. the. capillary. needle,. which. collect. on. a. grounded. plate.. Eventual. solvent.
evaporation.thereby.leaves.behind.a.ibrous.polymer.meshwork.(Doshi.and.Reneker.1995).
Nanoiber.characteristics.depend.on.various.processing.parameters,.including.the.nature.
of.the.polymer.solution.and.solvent,.operational.conditions.(e.g.,.distance.between.capillary.
and.collector,.applied.electric.ield),.and.environmental.temperature.and.humidity.(Li.and.Xia.
2004)..Electrospinning.allows.for.the.generation.of.long,.ultrathin.ibers.with.high.porosity.and.
high.surface-to-volume.ratio..Control.over.nanoiber.orientation.is.also.feasible..Indeed,.the.
ibrous.organization.can.have.a.profound.effect.on.cell.behavior..Electrospun.polyurethane.
(PU).nanoibers.in.an.aligned.coniguration.produced.human.ligament.ibroblasts.(HLFs).with.
morphology.reminiscent.of.those.found.in.vivo.and.synthesized.more.collagen.(correlated.to.
ECM.production).than.HLFs.seeded.on.randomly.oriented.electrospun.scaffolds..Applying.
uniaxial.strain.in.the.direction.of.alignment.further.enhanced.collagen.production.compared.
to.the.unstrained,.aligned.state.(Lee.et.al..2005)..In.another.case,.employing.an.external.factor,.
mesenchymal. stem. cells. (MSCs). seeded. on. aligned. poly(ε-caprolactone). (PCL). nanoibers.
were.subjected.to.orbital.shaking,.thereby.alleviating.the.persisting.problem.in.electrospun.
scaffolds. of. limited. cell. iniltration.. Collagen. content. also. increased. appreciably. and. more.
uniformly.along.the.scaffold.(Nerurkar.et.al..2011)..The.structure-function.relationship.of.a.
ibrous.scaffold.remains.an.important.parameter.to.optimize.tissue.regeneration.
