Biomedical Engineering Reference
In-Depth Information
which.includes.an.initial.mineral.dissolution.and.then.an.organic.phase.degradation.(Jang.
et.al.,.2009).
As.mentioned.above,.the.main.approach.in.the.tissue.engineering.process.is.mimicking.
the.ECM..Therefore,.for.bone.tissue.engineering.it.is.crucial.to.make.a.design.whose.prop-
erties.would.mimic.best.the.structure.and.function.of.bone.ECM..It.is.important.to.choose.
a.material.that.interacts.well.with.bone.cells.in.the.bone.formation.processes..Moreover,.
it.is.favorable.that.materials.with.good.mechanical.properties.and.can.withstand.various.
external.stresses.applied.on.bone.are.incorporated.into.the.material.design..Since.the.orga-
nization.of.all.bone.compartments.is.in.nanoscale.or.at.the.molecular.level,.a.nanoscale-
based.design.would.be.optimal.to.mimic.the.natural.bone..Various.strategies.have.been.
tried.in.designing.a.tissue.engineered.bone.
Both. synthetic. and. natural. materials. have. been. utilized. in. this. ield.. Among. all. poly-
meric.materials,.a.group.of.polyesters,.such.as.PLA,.PGA,.PCL,.poly(3-hydroxybutyric.acid).
(PHB),.and.their.copolymers,.has.been.the.most.extensively.studied.polymers.to.produce.
the.nanoibrous.system.for.the.regeneration.of.bone.tissues.(Burg.et.al.,.2000)..A.summary.of.
nano/microibrous.scaffolds.used.in.bone.tissue.engineering.studies.is.given.in.Table 10.1..
Yoshimoto.et.al..(2003).used.electrospun.PCL.nanoibers,.and.microscopic.analysis.of.mes-
enchymal.stem.cell-seeded.scaffolds.revealed.a.good.cell.penetration.in.addition.to.a.high.
level.of.mineralization.and.collagen.type.I.production.after.4.weeks.of.culture.(Yoshimoto.
et.al.,.2003)..Sombatmankhong.et.al..produced.mats.from.PHB,.poly(3-hydroxybutyrate-co-
3-hydroxyvalerate).(PHBV).and.their.50/50.w/w.blends.and.studied.the.biocompatibility.of.
these.mats.by.a.human.osteosarcoma.cell.line.(Saos-2).and.mouse.ibroblasts.(L929)..Both.
cells. adhered. well. on. all. types. of. ibrous. scaffolds;. however,. the. highest. alkaline. phos-
phatase.(ALP).activity.was.seen.on.the.PHB/PHBV.blend.(Sombatmankhong.et.al.,.2007).
In.another.study,.PLA.and.poly(ethylene.glycol).(PEG)-PLA.diblock.polymers.with.con-
trolled.topographies.and.chemistries.were.prepared.by.electrospinning.in.order.to.study.
the.inluence.of.surface.topography.and.iber.diameter.on.cell.behavior..In.the.presence.
of.osteogenic.factors.the.cell.numbers.on.ibrous.scaffolds.were.reported.to.be.equal.to.or.
higher.than.those.on.smooth.surfaces..Furthermore,.the.authors.indicated.an.increase.in.
cell.density.with.an.increase.in.iber.diameter.and.no.inluence.of.surface.substratum.on.
ALP.activity.(Badami.et.al.,.2006)..The.inluence.of.iber.diameter.on.cell.behavior.was.also.
studied.by.other.researchers..Ndreu.et.al.
(2008).studied.the.inluence.of.different.types.of.
nano/microibers.(diameter.range:.300.nm-1.5.µm).on.Saos-2.cells..Good.cell.adherence,.
proliferation,.and.iniltration.were.observed.on.all.types.of.scaffolds.(PHBV,.PHBV-PLGA,.
PHBV-P(L,DL)LA,.and.PHBV-PLLA);.however,.the.highest.number.of.cell.attachments.was.
observed. on. the. ibers. with. the. lowest. diameter. (PHBV-PLLA. iber. diameter:. ~350. nm).
when.the.scaffolds.were.examined.with.a.scanning.electron.microscope.(SEM).and.a.con-
focal.laser.scanning.microscope.(CLSM).(Figure 10.1).
Reed.and.his.co-workers.(2009).carried.out.a.study.on.the.reconstruction.of.a.compound.
tissue.based.on.the.fact.that.healing.does.not.occur.as.a.single.tissue
,
.but.as.a.compound.
one
,
. such. as. bone-periosteum-skin.. In. order. to. perform. this. study
,
. they. seeded. human.
foreskin. ibroblasts,. murine. keratinocytes
,
. and. periosteal. cells. on. PCL. nanoibers. and.
showed. that. these. scaffolds. supported. the. growth. of. all. these. cell. types.. Even. though.
keratinocytes.grew.randomly.throughout.the.scaffolds
,
.they.reported.improved.longevity.
of.the.cocultured.cells.and.a.strong.degree.of.osteoinduction..As.a.consequence,.construc-
tion.of.a.composite.tissue.has.been.reported.by.the.authors.
(
Reed.et.al.,.2009
)
.
Compared.to.the.synthetic.materials,.natural.materials.have.better.biocompatibility,.and.
more. importantly,. they. possess. the. main. cues. that. are. necessary. for. a. cell. to. attach. and.
grow..Natural.polymers.are.also.advantageous.in.that.they.can.be.degraded.by.naturally.
