92
Bacterial Cellulose
suitable.interaction.with.cells,.thus.methods.to.enhance.biocompatibility.are.
required.(Ma et.al..2007;.Wang et.al..2004).
The.surface.properties.of.a.scaffold,.such.as.wettability,.topography,.chemistry,.surface.charge,.the.presence.of.hydrophobic.and.hydrophilic.domains,.
density,.and.the.conformation.of.functional.groups,.all.play.a.crucial.role.in.
the.cell–material.interaction.(Vesel et.al..2008)..The.control.of.cell.adhesion.
on. the. polymer. substrate,. and. therefore. the. ability. to. guide. proliferation,.
migration,.and.differentiation,.is.highly.desirable.and.a.central.issue.in.the.
development.of.scaffolds.for.tissue.engineering.(Lucchesi.et.al..2008).
The.attachment.of.cells.to.biomedical.materials.can.be.improved.by.using.
adhesion. molecules,. present. in. the. extracellular. matrix. substances,. such. as.
fibronectin,.vitronectin,.or.laminin..A.binding.site.present.in.many.adhesive.
proteins.is.the.three.amino.acid.sequence.Arg-Gly–Asp.(RGD),.which.binds.
integrin.receptors.on.the.cell.surface.(Hersel.et.al..2003)..Proteins.(such as.those.
with.RGD.sequences).that.induce.desirable.cell.behaviors.(e.g., cell.adhesion,.
spreading,.and.other.functions).have.been.incorporated.into.. biomaterials.to.
control.tissue.reactions.
Bacterial.nanocellulose.(BNC).is.a.new.promising.material.as.a.replacement.for.small.blood.vessels..For.the.reconstruction.of.arteries.with.large.
caliber,. currently. available. synthetic. grafts. offer. a. reasonable. solution.
and. proven. clinical. efficacy.. However,. for. small-size. (<6. mm). grafts. these.
. materials. generally. give. poor. performance,. due. to. anastomotic. intimal.
hyperplasia.and.surface.thrombogenicity.(Bos.et.al..1998;.Conte.1998;.Zilla.
et.al..2007)..BNC.is.highly.biocompatible.in.vivo.(Helenius.et.al..2006),.but.
shows.poor.cell.adhesion..In.the.native.blood.vessel,.the.endothelium.creates. a. smooth. nonthrombogenic. surface.. In. order. to. sustain. cell. adhesion.
to.improve.blood.compatibility,.adhesive.peptides.have.been.introduced.on.
the.BNC.surface.through.different.techniques..Bodin.et.al..(2007).reported.
a.novel.method.to.activate.the.bacterial.cellulose.(BC).surface.with.the.RGD.
peptide. using. xyloglucan–Gly-Arg-Gly-Asp-Ser. (XG-GRGDS). conjugates..
The.surface.modification.of.BNC.with.XG,.in.water,.did.not.alter.the.morphology. of. the. fibers,. but. increased. the. wettability,. which. might. explain.
the. negligible. amount. of. protein. adsorbed. on. the. modified. material.. Cell.
adsorption. studies. showed. that. adhesion. of. human. endothelial. cells. is.
enhanced.when.the.BNC.hydrogel.is.modified.with.XG-GRGDS.(Bodin.et.al..
2007)..Moreover,.endothelial.cells.on.RGD-modified.BNC.showed.enhanced.
spreading.and.displayed.more.organized.stress.fibers.(thus.allowing.cellular.tension.to.be.maintained.and.modified.in.response.to.mechanical.stress),.
while.developing.a.more.mature.phenotype.(Fink.et.al..2011).
The.RGD.peptide.was.also.used.by.Andrade.et.al..(2010);.in.this.case.the.
adhesion.peptides.(RGD.or.Gly-Arg-Gly-Asp-Tyr.[GRGDY]).were.fused.to.a.
carbohydrate-binding.module.with.affinity.to.cellulose.(CBM3)..For.artificial.
grafts. based. on. cellulose,. the. use. of. a. CBM. exhibiting. specific. high. affinity.for.cellulose.surfaces.may.be.a.facile.and.smart.strategy.to.avoid.losing.
the.biological.agents.coating.the.graft..BNC.was.treated.with.recombinant.