178
Bacterial Cellulose
liquids. and. gases.. In. addition,. Mello. et. al.. (1997). pointed. out. the. low. foreign.body.reaction.of.BNC.as.a.substitute.material.for.the.dura.mater.after.
implantation.in.dogs..Good.biocompatibility.was.also.described.by.Klemm.
et. al.. (2001b). for. tubular-shaped. hollow. BNC. grafts. applied. as. prostheses.
for.blood.vessels..After.replacement.of.the.carotid.artery.in.rats,.there.was.a.
complete.incorporation.into.the.surrounding.tissue.without.any.macroscopically.observable.rejection.reaction..Histological.investigations.indicate.that.
the.whole.BNC.tube.was.coated.with.connective.tissue..No.signs.of.“inappropriate.inflammation”.were.detectable.after.4.weeks.of.implantation.(Klemm.
et.al..2001b)..In.addition,.the.in.vivo.biocompatibility.of.BNC.was.assessed.
by. implanting. flat-shaped. pieces. of. BNC. subcutaneously. into. rats. for. 1,. 4,.
and.12.weeks.(Helenius.et.al..2006)..Because.of.the.absence.of.any.chronic.
inflammatory.response,.multinuclear.giant.cells,.fibrosis,.or.encapsulation,.
the.authors.considered.BNC.as.a.biomaterial.with.good.biocompatibility.for.
tissue. engineering.. Similarly,. implantation. of. BNC. in. the. lumbar. subcutaneous.tissue.of.Swiss.albino.mice.for.a.maximum.time.of.90 days.resulted.
in.a.low.inflammatory.response.until.30.days.postsurgery,.but.induced.no.
chronic.foreign.body.reaction,.as.indicated.by.the.absence.of.multinuclear.
giant. cells. (Mendes. et. al.. 2009).. Finally,. BNC. was. applied. for. nasal. reconstruction.in.rabbits.by.elevating.the.dorsum.of.the.nose.(Lopes.et al..2009)..
BNC. was. used. as. a. cartilaginous. implant. for. 3 months. and. 6 months. in.
10 rabbits.each..At.both.time.points,.a.tendency.for.fragmentation.of.the.BNC.
grafts. was. observed,. accompanied. with. intense,. acute. inflammation. and.
partially.necrotic.skin.in.some.of.the.tested.animals..Despite.these.limited.
complications,.however,.the.authors.considered.BNC.as.biocompatible.and.a.
good.candidate.for.rhinoplasty.surgery.
The.results.from.in.vivo.studies.were.supported.by.biological.tests.in.vitro..
Cytotoxicity.tests.(e.g.,.MTT.assay,.a.colorimetric.assay.with.3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltertrazolium.bromide).are.mainly.used.to.screen.
biomaterials.for.their.potential.of.promoting.death.or.damage.at.the.cellular.
level.by.direct.lysis.or.by.fatally.altering.cellular.metabolism.(Bumgardner.
et.al..2008)..Most.studies.regarding.BNC.as.biocompatible.have.used.standardized.cell.lines.like.L929.cells.(Chen.et.al..2009).and.3T3.cells.(Cai.and.
Kim.2010;.Moreira.et.al..2009),.or.cell.lines.isolated.from.native.target.. tissues.
for. regeneration. purposes. (e.g.,. mesenchymal. stem. cells. [Gao. et. al.. 2011],.
urine-derived.stem.cells.[Bodin.et.al..2010],.smooth.muscle.cells.[Backdahl.
et.al..2006],.human.umbilical.vein.endothelial.cells.[Recouvreux.et.al..2011],.
osteoblast.cells.[Chen.et.al..2009],.or.chondrocytes.[Svensson.et.al..2005])..The.
interaction. of. BNC. with. cells. clearly. depends. on. specific. cell-type. aspects.
such.as.their.adhesion.and.proliferation.capability..For.example,.Chen.et.al..
(2009). observed. that. osteoblasts. are. more. susceptible. for. cytotoxicity. than.
standardized.and.commercially.available.L929.cells..The.authors.pointed.out.
that.tissue-derived.functional.cells.are.more.suitable.than.cell.lines.to.evaluate.the.cytotoxicity.of.a.biomaterial.with.respect.to.its.application.site.and.its.
suitability.for.the.regeneration.of.specific.tissues.or.organs.
Bacterial Cellulose
liquids. and. gases.. In. addition,. Mello. et. al.. (1997). pointed. out. the. low. foreign.body.reaction.of.BNC.as.a.substitute.material.for.the.dura.mater.after.
implantation.in.dogs..Good.biocompatibility.was.also.described.by.Klemm.
et. al.. (2001b). for. tubular-shaped. hollow. BNC. grafts. applied. as. prostheses.
for.blood.vessels..After.replacement.of.the.carotid.artery.in.rats,.there.was.a.
complete.incorporation.into.the.surrounding.tissue.without.any.macroscopically.observable.rejection.reaction..Histological.investigations.indicate.that.
the.whole.BNC.tube.was.coated.with.connective.tissue..No.signs.of.“inappropriate.inflammation”.were.detectable.after.4.weeks.of.implantation.(Klemm.
et.al..2001b)..In.addition,.the.in.vivo.biocompatibility.of.BNC.was.assessed.
by. implanting. flat-shaped. pieces. of. BNC. subcutaneously. into. rats. for. 1,. 4,.
and.12.weeks.(Helenius.et.al..2006)..Because.of.the.absence.of.any.chronic.
inflammatory.response,.multinuclear.giant.cells,.fibrosis,.or.encapsulation,.
the.authors.considered.BNC.as.a.biomaterial.with.good.biocompatibility.for.
tissue. engineering.. Similarly,. implantation. of. BNC. in. the. lumbar. subcutaneous.tissue.of.Swiss.albino.mice.for.a.maximum.time.of.90 days.resulted.
in.a.low.inflammatory.response.until.30.days.postsurgery,.but.induced.no.
chronic.foreign.body.reaction,.as.indicated.by.the.absence.of.multinuclear.
giant. cells. (Mendes. et. al.. 2009).. Finally,. BNC. was. applied. for. nasal. reconstruction.in.rabbits.by.elevating.the.dorsum.of.the.nose.(Lopes.et al..2009)..
BNC. was. used. as. a. cartilaginous. implant. for. 3 months. and. 6 months. in.
10 rabbits.each..At.both.time.points,.a.tendency.for.fragmentation.of.the.BNC.
grafts. was. observed,. accompanied. with. intense,. acute. inflammation. and.
partially.necrotic.skin.in.some.of.the.tested.animals..Despite.these.limited.
complications,.however,.the.authors.considered.BNC.as.biocompatible.and.a.
good.candidate.for.rhinoplasty.surgery.
The.results.from.in.vivo.studies.were.supported.by.biological.tests.in.vitro..
Cytotoxicity.tests.(e.g.,.MTT.assay,.a.colorimetric.assay.with.3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltertrazolium.bromide).are.mainly.used.to.screen.
biomaterials.for.their.potential.of.promoting.death.or.damage.at.the.cellular.
level.by.direct.lysis.or.by.fatally.altering.cellular.metabolism.(Bumgardner.
et.al..2008)..Most.studies.regarding.BNC.as.biocompatible.have.used.standardized.cell.lines.like.L929.cells.(Chen.et.al..2009).and.3T3.cells.(Cai.and.
Kim.2010;.Moreira.et.al..2009),.or.cell.lines.isolated.from.native.target.. tissues.
for. regeneration. purposes. (e.g.,. mesenchymal. stem. cells. [Gao. et. al.. 2011],.
urine-derived.stem.cells.[Bodin.et.al..2010],.smooth.muscle.cells.[Backdahl.
et.al..2006],.human.umbilical.vein.endothelial.cells.[Recouvreux.et.al..2011],.
osteoblast.cells.[Chen.et.al..2009],.or.chondrocytes.[Svensson.et.al..2005])..The.
interaction. of. BNC. with. cells. clearly. depends. on. specific. cell-type. aspects.
such.as.their.adhesion.and.proliferation.capability..For.example,.Chen.et.al..
(2009). observed. that. osteoblasts. are. more. susceptible. for. cytotoxicity. than.
standardized.and.commercially.available.L929.cells..The.authors.pointed.out.
that.tissue-derived.functional.cells.are.more.suitable.than.cell.lines.to.evaluate.the.cytotoxicity.of.a.biomaterial.with.respect.to.its.application.site.and.its.
suitability.for.the.regeneration.of.specific.tissues.or.organs.