190
Bacterial Cellulose
It.is.a.key.advantage.of.BNC.that.the.tubular.implants.can.be.produced.
directly.during.biofabrication..The.type.and.construction.of.the.bioreactor.
produce. a. specific. design. of. nanofiber. network. structure,. shape,. and. surface.quality.of.the.implant..The.corresponding.patented.matrix.technology.
(Klemm.et.al..2001a).operates.by.forming.the.tubular.implant.on.a.matrix.
in.contact.with.the.culture.medium..After.removal.from.the.bioreactor,.and.
subsequent.purification.and.sterilization,.the.tubes.are.ready.to.be.used.as.
stable.vascular.conduits.for.animal.surgery..In.addition,.these.tubes.are.suitable.as.training.material.for.surgeons.(e.g.,.in.microsurgical.techniques).
In.a.first.microsurgical.study,.small.BNC.implants.were.attached.to.artificial.defects.of.the.carotid.arteries.of.a.rat.for.1.year..These.long-term.results.
showed. the. incorporation. of. BNC. tubes. under. a. formation. of. neointima.
(the inner. . lining. of. an. artery. or. vein. or. lymphatic. vessel). and. ingrowth.
of. active. fibroblasts. (Klemm. et. al.. 2001b,. 2005,. 2006).. In. a. second. study.
(Schumann.et al..2009),.tubes.of.BNC.were.generated.with.a.length.of.10.mm,.
an.inner.diameter.of.3.0–3.7.mm,.and.a.wall.thickness.of.0.6–1.0.mm..Shaping.
of.the.tube.wall,.as.well.as.calibration.of.the.inner.diameter,.is.performed.by.
the.matrix.technology.using.a.glass.mandril.of.the.respective.size..Whereas.
BNC. tubes. produced. by. this. technology. (BActerial. SYnthesized. Cellulose.
[BASYC]). are. characterized. by. a. smooth. inner. surface,. common. vascular.
grafts.(Dacron.and.expanded.PTFE.[ePTFE]).show.an.increased.roughness.
of.the.inner.surfaces,.as.demonstrated.by.confocal.laser.scanning.microscopy.
(LSM).(Figure 9.6)..In.the.case.of.Dacron,.single.polyester.filaments.are.visible.
(Figure 9.6a),.while.ePTFE.shows.channels.caused.by.the.expansion.during.
manufacturing. (Figure 9.6b).. With. its. smooth. surface. (Figure 9.6e),. BASYC.
closely. resembles. the. inner. wall. of. human. arteries. and. veins. (Figures 9.6c.
and.9.6d).
BASYC.vascular. grafts.were. used. to.replace. the.carotid.arteries. of.eight.
pigs.. After. a. follow-up. period. of. 3. months,. the. grafts. were. removed. and.
analyzed.both.macroscopically.and.microscopically..The.aim.of.this.study.
was.to.evaluate.the.new.cylindrical.BNC.biomaterial.as.a.potential.bioactive.
scaffold.for.small.arterial.substitutes.
In. detail,. the. animals. were. heparinized. systemically. with. an. intravenous.
bolus.injection.of.200.units/kg.body.weight.and.the.right.carotid.artery.was.
carefully.prepared..The.target.artery.was.then.resected.and.the.BNC.graft.was.
inserted.by.interrupted.suture.using.7-0.monofilament.polypropylene.(Prolene
; .
Ethicon,.Hamburg,.Germany)..Complete.hemostasis.occurred.rapidly.following.a.short.period.of.oozing.through.the.graft.after.declamping..To.assess.the.
patency. of. the. grafts,. flow. measurement. (MediStim. AS,. Oslo,. Norway). was.
carried.out.at.a.mean.blood.pressure.of.70.mmHg..After.wound.closure,.all.
animals.were.allowed.to.grow.for.3.months.in.a.stable.with.free.access.to.food.
and. water.. After. 3. months. the. carotid. artery. with. the. implanted. graft. was.
harvested.en.bloc.and.the.implants.were.evaluated.for.chronic.inflammation,.
foreign.body.responses,.cell.ingrowth,.and.diameter.using.light.and.electron.
microscopy.(LEO.1450.VP/REM,.Oberkochen-Zeiss,.Germany).