96
Bacterial Cellulose
port.structures.in.tissue.engineering.of.cartilage.should.fulfill.some.requirements.in.order.to.comply.with.potential.clinical.applications..They.should.
be.biocompatible,.able.to.aid.in.cell.development.and.differentiation,.have.
the.porosity.necessary.to.support.cell.ingrowth,.allow.for.efficient.nutrition.
and.gas.exchange,.and.have.a.suitable.degradation.rate,.able.to.cope.with.the.
formation.of.new.tissue,.in.order.to.maintain.the.mechanical.stability.of.the.
system.(Hutmacher.2000;.Svensson.et.al..2005).
In. order. to. mimic. the. glucosaminoglycans. of. cartilage. tissue. in. vivo,.
Svensson. et. al.. (2005). added. surface. charges. through. phosphorylation. and.
sulfation. on. BNC. matrices.. The. materials. were. analyzed. for. mechanical.
properties,. microstructure,. and. cell–material. interactions. in. order. to. assess.
the.potential.of.this.matrix.as.a.scaffold.for.cartilage.tissue.engineering..The.
compressive.modulus.of.the.phosphorylated.samples.increased.with.the.reaction.time.and.improved.with.regard.to.native.BNC..This.result.was.probably.
due.to.the.more.compact.structure.of.the.three-dimensional.(3D).network.in.
the.modified.material..An.even.more.compact.network.structure.was.found.
in. sulfated. BNC,. which. showed. a. greater. resistance. to. compressive. forces..
Sulfated-BNC.had.a.significantly.lower.Young’s.modulus.than.the.unmodified.
one,.resulting.in.a.reduction.of.the.mechanical.integrity..The.lower.strength.
of.sulfated-BNC.may.be.due.to.the.prevention.of.hydrogen.bonding.between.
the.cellulose.chains.by.the.covalently.bonded.sulfate.groups,.chain.scission.
by.acid.hydrolysis,.or.a.combination.of.these..Native.and.chemically.modified.BNC.materials.were.evaluated.for.cell.interaction.studies.using.bovine.
chondrocytes..The.unmodified.BNC.supports.chondrocyte.proliferation.of.up.
to.50%.of.the.levels.obtained.using.the.native.tissue.substrate,.. collagen.type II..
However,. in. comparison. with. tissue. culture. plastic. and. . calcium. alginate,.
unmodified. BC. showed. significantly. higher. levels. of. chondrocyte. growth..
Chemical.sulfation.and.phosphorylation.of.the.BNC,.performed.to.mimic.the.
glucosaminoglycans.of.native.cartilage,.did.not.enhance.chondrocyte.growth..
It.was.verified.that.BNC.supports.cell.ingrowth,.and.chondrocytes.preserve.
the.differentiated.phenotype..In.general,.BNC.appeared.to.have.potential.as.a.
scaffold.for.tissue.engineering.of.cartilage.
The.modification.of.surfaces.using.plasma.techniques.is.becoming.increasingly. common. in. biomaterials. engineering.. The. most. important. advantage.
of.plasma.surface.modifications.is.the.ability.to.selectively.change.the.surface.properties,.improving.biocompatibility.and.mimicking.the.local.tissue.
environment.without.altering.the.bulk.attributes..Furthermore,.it.is.an.easy.
way.to.introduce.the.desired.groups.or.polymer.chains.onto.the.surface.of.
materials.with.complex.shapes..Plasma.thus.provides.a.versatile.and.effective.
means. to. modify. surfaces,. enhancing. the. physicochemical. properties. and.
optimizing.the.biofunctionality.(Chu.et.al..2002)..Pertile.et.al..(2010).modified.
BNC.membranes.with.nitrogen.plasma.in.order.to.enhance.the.cell–material.
interactions.through.the.incorporation.of.N-groups.on.the.. surface..The.results.
showed.that.the.nitrogen.plasma.treatment.did.not.increase.the.wettability.