Wound Dressings and Cosmetic Materials from Bacterial Nanocellulose
165
To. impregnate. colloidal. silver. submicron. particles. into. bacterial. cellulose,.
Maria.et.al..(2009).soaked.them.in.AgNO 3 .solution.and.then.treated.them.with.
reducing.agents.(hydrazine,.hydroxylamine,.or.ascorbic.acid).in.solutions.of.
either.polyvinylpyrrolidone.or.gelatin.used.as.colloid.protectors..The.resulting. composites. were. dried. and. subjected. to. ash. content. assay. and. thermogravimetric.analysis.to.determine.the.level.of.silver.loading..However,.neither.
the.swelling.capacity.nor.antibacterial.activity.of.these.membranes.was.tested.
Pinto.et.al..(2009),.who.fabricated.nanocomposites.of.silver.and.bacterial.
or.plant.cellulose,.applied.two.different.methods.of.reduction.of.Ag + .ions..
Bacterial.cellulose.membranes.were.immersed.in.AgNO 3 .solution.and.then.
treated.with.either.an.excess.of.sodium.borohydride.or.ultraviolet.(UV).radiation.. The. resulting. nanocomposites. displayed. bacteriostatic. effect. against.
Bacillus subtilis,.S..aureus,.and.Klebsiella pneumonia.at.silver.nanoparticle.concentrations.of.5.0.×.10 −4 .wt%..Their.antimicrobial.activity.increased.with.the.
concentration.of.Ag 0 .nanoparticles.
Fabrication.of.nanosilver-coated.bacterial.cellulose.displaying.antimicrobial.activity.is.also.described.in.U.S..Patent.application.12,226,669.(Table 8.3)..
To.obtain.the.composite.material,.a.suspension.of.cellulose.fibers.was.first.
oxidized.to.form.dialdehyde.cellulose.fibers,.after.which.a.functional.group.
(e.g.,.thio-).was.incorporated..The.functionalized.cellulose.fibers.were.then.
exposed.to.an.aqueous.solution.of.silver.compound.(e.g.,.silver.proteinate),.
causing.the.formation.of.nanosilver.particles.that.were.bound.to.the.functionalized.cellulose.fibers..These.nanosilver.particles.were.further.grown.by.
exposing.them.to.a.solution.containing.a.second.silver.compound.(e.g., silver. .
ammonia).. The. silver-coated. bacterial. cellulose. displayed. antimicrobial.
activity.towards.E. coli.and.S..aureus.
Another. U.S.. Patent. application. (12,034,629;. Table 8.3). describes. a. photoactivated.BNC.wound.dressing.with.antimicrobial.activity.made.of.bacterial.
. cellulose. hydrogel. membrane. containing. immobilized. photocatalytic. particles..The.membrane.displays.antimicrobial.activity.when.the.photo. catalytic.
particles.are.exposed.to.light,.which.triggers.the.generation.of.reactive.. oxygen.
species.capable.of.reacting.with.microbes.and.killing.them..The.method.is.
based.on.photocatalytic.oxidation.using.metal.oxide.catalysts.like.TiO 2 .that.
generate. species. like. hydroxyl. radical,. hydrogen. peroxide,. and. superoxide..
The.TiO 2 -impregnated.BNC.membrane.was.made.by.adding.a.TiO 2 .suspension.to.a.cleaned.bacterial.cellulose.membrane.in.a.vacuum.filtration.unit.
Wei. et. al.. (2011). used. benzalkonium. chloride. to. fabricate. freeze-dried.
BNC.membranes.with.antimicrobial.properties.destined.for.certain.practical.
applications.such.as.the.treatment.of.acute.traumas..For.this.purpose,.BNC.
membranes.synthesized.by.a.G. xylinus.strain.were.thoroughly.purified.to.
eliminate.bacterial.cells.and.other.impurities,.cut.into.disks.(a.diameter.of.
15.mm),.freeze-dried.for.24.h,.and.soaked.for.24.h.in.benzalkonium.chloride.
solutions.(concentrations.ranging.from.0.003%.to.0.102%)..The.non. absorbed.
benzalkonium.chloride.was.removed.from.the.BNC.disks.by.a.10.s.immersion. in. distilled. water. and. wiping. with. filter. paper.. The. resulting. films.
165
To. impregnate. colloidal. silver. submicron. particles. into. bacterial. cellulose,.
Maria.et.al..(2009).soaked.them.in.AgNO 3 .solution.and.then.treated.them.with.
reducing.agents.(hydrazine,.hydroxylamine,.or.ascorbic.acid).in.solutions.of.
either.polyvinylpyrrolidone.or.gelatin.used.as.colloid.protectors..The.resulting. composites. were. dried. and. subjected. to. ash. content. assay. and. thermogravimetric.analysis.to.determine.the.level.of.silver.loading..However,.neither.
the.swelling.capacity.nor.antibacterial.activity.of.these.membranes.was.tested.
Pinto.et.al..(2009),.who.fabricated.nanocomposites.of.silver.and.bacterial.
or.plant.cellulose,.applied.two.different.methods.of.reduction.of.Ag + .ions..
Bacterial.cellulose.membranes.were.immersed.in.AgNO 3 .solution.and.then.
treated.with.either.an.excess.of.sodium.borohydride.or.ultraviolet.(UV).radiation.. The. resulting. nanocomposites. displayed. bacteriostatic. effect. against.
Bacillus subtilis,.S..aureus,.and.Klebsiella pneumonia.at.silver.nanoparticle.concentrations.of.5.0.×.10 −4 .wt%..Their.antimicrobial.activity.increased.with.the.
concentration.of.Ag 0 .nanoparticles.
Fabrication.of.nanosilver-coated.bacterial.cellulose.displaying.antimicrobial.activity.is.also.described.in.U.S..Patent.application.12,226,669.(Table 8.3)..
To.obtain.the.composite.material,.a.suspension.of.cellulose.fibers.was.first.
oxidized.to.form.dialdehyde.cellulose.fibers,.after.which.a.functional.group.
(e.g.,.thio-).was.incorporated..The.functionalized.cellulose.fibers.were.then.
exposed.to.an.aqueous.solution.of.silver.compound.(e.g.,.silver.proteinate),.
causing.the.formation.of.nanosilver.particles.that.were.bound.to.the.functionalized.cellulose.fibers..These.nanosilver.particles.were.further.grown.by.
exposing.them.to.a.solution.containing.a.second.silver.compound.(e.g., silver. .
ammonia).. The. silver-coated. bacterial. cellulose. displayed. antimicrobial.
activity.towards.E. coli.and.S..aureus.
Another. U.S.. Patent. application. (12,034,629;. Table 8.3). describes. a. photoactivated.BNC.wound.dressing.with.antimicrobial.activity.made.of.bacterial.
. cellulose. hydrogel. membrane. containing. immobilized. photocatalytic. particles..The.membrane.displays.antimicrobial.activity.when.the.photo. catalytic.
particles.are.exposed.to.light,.which.triggers.the.generation.of.reactive.. oxygen.
species.capable.of.reacting.with.microbes.and.killing.them..The.method.is.
based.on.photocatalytic.oxidation.using.metal.oxide.catalysts.like.TiO 2 .that.
generate. species. like. hydroxyl. radical,. hydrogen. peroxide,. and. superoxide..
The.TiO 2 -impregnated.BNC.membrane.was.made.by.adding.a.TiO 2 .suspension.to.a.cleaned.bacterial.cellulose.membrane.in.a.vacuum.filtration.unit.
Wei. et. al.. (2011). used. benzalkonium. chloride. to. fabricate. freeze-dried.
BNC.membranes.with.antimicrobial.properties.destined.for.certain.practical.
applications.such.as.the.treatment.of.acute.traumas..For.this.purpose,.BNC.
membranes.synthesized.by.a.G. xylinus.strain.were.thoroughly.purified.to.
eliminate.bacterial.cells.and.other.impurities,.cut.into.disks.(a.diameter.of.
15.mm),.freeze-dried.for.24.h,.and.soaked.for.24.h.in.benzalkonium.chloride.
solutions.(concentrations.ranging.from.0.003%.to.0.102%)..The.non. absorbed.
benzalkonium.chloride.was.removed.from.the.BNC.disks.by.a.10.s.immersion. in. distilled. water. and. wiping. with. filter. paper.. The. resulting. films.