Bacterial Nanocellulose Hydrogels Designed as Bioartificial Medical Implants 177
Suitability of BNC as a Biomaterial
Biomaterials.must.fulfill.certain.properties.to.be.suitable.for.use.in.medicine..
Generally.these.requirements.can.be.classified.into.the.following.broad.features:.biocompatibility,.functionality,.and.sterilizability..These.features.will.
be.considered.for.BNC.with.respect.to.applications.in.regenerative.medicine..
In. particular,. the. functionality. of. BNC. will. be. thoroughly. discussed. concerning.the.interdisciplinary.aspects.of.bioactivity,.biodegradation,.porosity,.
and.mechanical.properties.
Biocompatibility
The. interaction. of. a. material. with. cells,. tissue,. or. whole. organisms. without. toxic. or. immunological. effects. may. be. regarded. as. biocompatibility.
(Bumgardner. et. al.. 2008).. The. diversity. of. biomaterials. used. for. medical.
devices.is.broad.and.the.choice.of.a.given.biomaterial.is.driven.by.its.desired.
function,.anatomical.location,.and.application.time..The.contact.of.biomaterials.with.body.tissue.may.be.only.for.a.short.time,.up.to.10–15.years,.or.even.
for.the.lifetime.of.a.patient..This.variance.in.biomaterial.use.led.to.the.general.definition.that.biocompatibility.is.“the.ability.of.a.material.to.perform.
with. an. appropriate. host. reaction. in. specific. application”. (Williams. 1999)..
Evaluation.of.the.biocompatibility.of.a.material.includes.characterization.of.
the.material’s. properties. (chemical. composition,. biodegradability,. porosity,.
mechanical.properties,.and.surface.properties).as.well.as.biological.testing..
In. vitro. biocompatibility. tests. offer. reproducible. and. standardized. conditions.and.are.relatively.cheap.in.comparison.to.in.vivo.tests..However,.the.
in.vitro.performance.of.a.biomaterial.does.not.necessarily.reflect.its.characteristics.in.vivo,.because.environmental.factors.such.as.complex.interactions.
between. the. biomaterial. and. surrounding. cells. or. tissues,. biomechanical.
strain,.as.well.as.hormonal.factors.may.be.not.considered.in.these.assays.
For.BNC,.both.in.vitro.and.in.vivo.tests.have.been.performed..Before.the.
interest.in.BNC.as.a.biomaterial.in.regenerative.medicine.and.tissue.engineering,. either. cellulose. of. plant. origin,. regenerated. cellulose,. or. cellulose.
derivatives. (e.g.,. cellulose. acetate,. cellulose. phosphate). showed. high. biocompatibility. with. negligible. foreign. body. reactions. and. immunological.
responses.(Martson.et.al..1998;.Miyamoto.et.al..1989)..Because.of.the.diverse.
properties.of.BNC,.the.in.vivo.interaction.between.the.material.and.the.adjacent.tissues.had.to.be.characterized.in.detail.and.compared.to.that.of.. cellulose.
materials.of.plant.origin..For.example,.BNC.membranes.do.not.cause.skin.
irritation.and.are.therefore.suitable.as.an.artificial.skin.for.temporary.covering.of.wounds.in.human.and.veterinary.medicine.(Fontana.et al..1990;.Jonas.
and.Farah.1998;.Klemm.et.al..2001b)..This.is.particularly.true.in.view.of.their.
great.mechanical.strength.in.the.wet.state.and.substantial.permeability.for.