Biomedical Engineering Reference
In-Depth Information
However,.ceramics.have.some.drawbacks,.like.fragility,.brittleness,.low.tensile.strength,.
and.being.mostly.not.biodegradable..Biological.and.synthetic.polymeric.materials.have.
been.widely.used.in.various.tissue.engineering.applications.due.to.their.degradability,.
biocompatibility,.mechanical.properties.suitable.for.many.applications,.and.ease.of.pro-
cessability..Some.examples.of.natural.biodegradable.polymers.are.collagen,.ibrinogen,.
gelatin,.chitosan,.cellulose,.alginate,.starch,.silk,.and.hyaluronic.acid..The.main.advan-
tages. of. these. materials. are. their. low. immunogenicity,. bioactivity,. capability. of. inter-
acting. with. the. host. tissue,. chemical. versatility,. and. availability. from. various. sources,.
as.in.starch.and.chitosan..Of.these,.collagen,.ibrin,.hyaluronic.acid,.agarose,.chitosan,.
and.alginate.are.materials.especially.used.in.the.production.of.scaffolds.for.engineering.
of.bone.and.cartilage.(Sabir.et.al.,.2009)..The.most.widely.used.synthetic.polymers.are.
a. family. of. linear. aliphatic. polyesters,. poly(α-hydroxy. acid). (PHA),. such. as. poly(lactic.
acid). (PLA),. poly(glycolic. acid). (PGA),. and. their. copolymer. poly(lactic. acid-co-glycolic.
acid).(PLGA).(Mooney.et.al.,.1996;.Seal.et.al.,.2001)..For.example,.PGA.has.been.used.in.
the.engineering.of.cartilage,.tendon,.ureter,.intestine,.blood.vessel,.heart.valve,.and.other.
tissues.. Poly(ε-caprolactone). (PCL),. poly(propylene. fumarate). (PPF),. poly(carbonate),.
poly(phosphazenes),. poly(phosphoesters). and. poly(anhydrides),. tyrosine-derived. poly-
mers,. and. biodegradable. urethane-based. polymers. are. other. important. synthetic,. bio-
degradable.polymers.used.in.tissue.engineering.applications..A.problem.with.synthetic.
polymers. is. their. degradation. products,. which. may. reduce. the. local. pH,. induce. an.
inlammatory.response,.or.create.some.adverse.reactions.and.being.nonbiocompatible.
In.the.past.few.years,.polymer-ceramic.composites.have.gained.increased.importance.in.
the.engineering.of.several.types.of.tissues,.such.as.bone,.cartilage,.tendon,.and.ligament.
(Marra.et.al.,.1999;.Zhang.and.Ma,.1999;.Ma.et.al.,.2001;.Zhao.et.al.,.2002;.Liu.and.Ma,.2004)..
The.composite.is.expected.to.have.improved.compressive.mechanical.properties.compared.
to.the.polymer,.and.better.structural.integrity.and.lexibility.than.ceramics,.and.thus.the.
combination.of.ceramic.and.polymer.created.reinforced.porous.scaffolds.with.enhanced.
bioactivity.and.controlled.resorption.rates.(Zhang.and.Ma,.1999;.Ma.et.al.,.2001).
During. the. selection. of. a. scaffold. material,. an. important. step. is. to. decide. on. the. fab-
rication. technique.. The. processing. technique. is. expected. not. to. change. certain. material.
properties,. like. biocompatibility. and. surface. chemistry.. The. technique. should. be. repro-
ducible. in. terms. of. scaffold. porosity,. pore. size,. pore. distribution,. and. interconnectivity.
(Leong.et.al.,.2003)..There.are.many.techniques.that.can.be.used.to.process.materials.into.
scaffolds,.such.as.solvent.casting,.phase.inversion,.iber.bonding,.melt-based.technologies,.
high-pressure-based.methods,.freeze.drying,.and.rapid.prototyping.(Ma.and.Langer,.1999;.
Kinikoglu.et.al.,.2009;.Sangsanoh.et.al.,.2009;.Yilgor.et.al.,.2008;.Vrana.et.al.,.2007;.Zorlutuna.
et.al.,.2007;.Mooney.et.al.,.1996;.Thomson.et.al.,.1995;.Mikos.et.al.,.1993)..Each.production.
technique.has.some.disadvantages.and.advantages.over.the.others.and.may.not.be.appli-
cable.to.some.polymers..Therefore,.appropriate.processing.techniques.should.be.chosen.to.
produce.a.scaffold.with.the.desired.properties.for.the.speciic.application.
To.date,.scaffolds.have.been.produced.in.our.group.in.various.forms,.like.foam.(Zorlutuna.
et.al.,.2008;.Kinikoglu.et.al.,.2009,.Dogan.et.al.,.2009,.Ulubayram.et.al.,.2001),.ilm.(Vrana.
et.al.,.2007;.Zorlutuna.et.al.,.2007;.Kenar.et.al.,.2008;.Zorlutuna.et.al.,.2009),.and.ibers.(Ndreu.
et.al.,.2008;.Kenar.et.al.,.2009;.Yucel.et.al.,.2010),.each.having.different.chemistries,.and.a.
number.of.studies.have.been.carried.out.with.them.either.in.vitro
or.in.vivo..In.the.last.
decades,.foam.and.ilm-based.scaffolds.were.popular.for.3D.and.2D.applications;.however,.
in.recent.years.there.has.been.an.increase.in.the.use.of.ibrous.scaffolds,.especially.made.
by.electrospinning.
