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Bacterial Cellulose
Microbial.cellulose.hydrogels.can.play.not.only.the.role.of.wound.dressings,. but. they. can. also. be. used. for. transdermal. delivering. of. biologically.
active.agents.penetrating.through.the.stratum corneum.(U.S..Patent.application.11,406,528,.assignee:.Xylos.Corporation,.filed.in.April.2006)..Controlled.
local.drug.release.systems.are.known.to.offer.many.advantages.over.traditional.delivery.methods.such.as.ingestion,.injection,.or.inhalation,.since.they.
provide.a.constant.drug.concentration.at.the.delivery.site,.lower.drug.levels. .
in. the. patient,. and. reduced. risk. of. harmful. side. effects.. One. of. the. most.
important. parameters. characterizing. such. systems. is. the. rate. of. drug. diffusion,.which.was.found.to.be.changed.by.γ-irradiation.(Stoica-Guzun.et.al..
2007)..Investigation.of.tetracycline.permeation.through.irradiated.(doses.of.
either.5.or.15.kGy).and.nonirradiated.bacterial.cellulose.membranes.showed.
that. the. diffusion. was. faster. through. the. latter.. The. decrease. in. bacterial.
. cellulose.membrane.permeability.and.adsorption.capacity.was.caused.by.its.
shrinkage,.and.probably.by.formation.of.radiolysis.products..Regardless.of.
this.subtle.change.in.properties,.γ-irradiated.BNC.hydrogels.can.be.used.as.
transdermal.drug.delivery.systems.
BNC Dressings with Antimicrobial Properties
Antimicrobial. properties. of. BNC-based. wound. dressings. can. be. achieved.
by.incorporation.of.appropriate.compounds..Additives.that.are.used.for.this.
purpose.in.wound.management.include.silver-based.compounds,.chlorhexidine. gluconate,. benzalkonium. chloride,. parabens,. and. polyhexamethylene.
biguanide. hydrochloride. (PHMB).. Some. of. these. substances. have. been.
embedded.in.BNC.hydrogels.to.achieve.antimicrobial.activity.
Bacterial. cellulose–silver. nanocomposites. that. are. potentially. applicable.
in. wound. treatment. were. obtained. by. various. methods.. To. produce. silver.
nanoparticles. uniformly. distributed. throughout. bacterial. cellulose. membranes,.Maneerung.et.al..(2008).immersed.them.in.silver.nitrate.solution.and.
then.the.silver.ions.(Ag + ).were.reduced.by.sodium.borohydride.to.Ag 0 ..This.
process. was. controlled. by. measurements. of. absorbance. at. approximately.
420. nm,. which. is. characteristic. of. silver. nanoparticles,. the. size. of. which. is.
affected. by. the. NaBH 4 :AgNO 3 . ratio.. Also,. X-ray. diffraction. provided. evidence. of. silver. nanoparticle. formation.. The. impregnated. BNC. membranes.
were.then.freeze-dried..They.showed.strong.activity.against.Escherichia coli.
and. Staphylococcus aureus.. Although. dried. BNC. membranes. are. known. to.
display.a.much.lower.water.absorption.performance.and.swelling.ratio.than.
the.never-dried.ones,.they.are.superior.in.terms.of.convenience,.stability,.and.
portability.. The. freeze-dried. silver. nanoparticle-impregnated. membranes.
fabricated.by.Maneerung.et.al..(2008).displayed.high.swelling.ability,.as.they.
absorbed.62.25.times.their.own.weight.in.water.after.immersion.in.deionized.
water.for.4.h..This.high.swelling.ratio.provides.evidence.that.the.freeze-dried.
bacterial.cellulose.maintains.its.porous.3D.structure.and.can.suck.the.molecules.of.water.into.capillaries.within.the.network.of.nanofibers.more.easily.
Bacterial Cellulose
Microbial.cellulose.hydrogels.can.play.not.only.the.role.of.wound.dressings,. but. they. can. also. be. used. for. transdermal. delivering. of. biologically.
active.agents.penetrating.through.the.stratum corneum.(U.S..Patent.application.11,406,528,.assignee:.Xylos.Corporation,.filed.in.April.2006)..Controlled.
local.drug.release.systems.are.known.to.offer.many.advantages.over.traditional.delivery.methods.such.as.ingestion,.injection,.or.inhalation,.since.they.
provide.a.constant.drug.concentration.at.the.delivery.site,.lower.drug.levels. .
in. the. patient,. and. reduced. risk. of. harmful. side. effects.. One. of. the. most.
important. parameters. characterizing. such. systems. is. the. rate. of. drug. diffusion,.which.was.found.to.be.changed.by.γ-irradiation.(Stoica-Guzun.et.al..
2007)..Investigation.of.tetracycline.permeation.through.irradiated.(doses.of.
either.5.or.15.kGy).and.nonirradiated.bacterial.cellulose.membranes.showed.
that. the. diffusion. was. faster. through. the. latter.. The. decrease. in. bacterial.
. cellulose.membrane.permeability.and.adsorption.capacity.was.caused.by.its.
shrinkage,.and.probably.by.formation.of.radiolysis.products..Regardless.of.
this.subtle.change.in.properties,.γ-irradiated.BNC.hydrogels.can.be.used.as.
transdermal.drug.delivery.systems.
BNC Dressings with Antimicrobial Properties
Antimicrobial. properties. of. BNC-based. wound. dressings. can. be. achieved.
by.incorporation.of.appropriate.compounds..Additives.that.are.used.for.this.
purpose.in.wound.management.include.silver-based.compounds,.chlorhexidine. gluconate,. benzalkonium. chloride,. parabens,. and. polyhexamethylene.
biguanide. hydrochloride. (PHMB).. Some. of. these. substances. have. been.
embedded.in.BNC.hydrogels.to.achieve.antimicrobial.activity.
Bacterial. cellulose–silver. nanocomposites. that. are. potentially. applicable.
in. wound. treatment. were. obtained. by. various. methods.. To. produce. silver.
nanoparticles. uniformly. distributed. throughout. bacterial. cellulose. membranes,.Maneerung.et.al..(2008).immersed.them.in.silver.nitrate.solution.and.
then.the.silver.ions.(Ag + ).were.reduced.by.sodium.borohydride.to.Ag 0 ..This.
process. was. controlled. by. measurements. of. absorbance. at. approximately.
420. nm,. which. is. characteristic. of. silver. nanoparticles,. the. size. of. which. is.
affected. by. the. NaBH 4 :AgNO 3 . ratio.. Also,. X-ray. diffraction. provided. evidence. of. silver. nanoparticle. formation.. The. impregnated. BNC. membranes.
were.then.freeze-dried..They.showed.strong.activity.against.Escherichia coli.
and. Staphylococcus aureus.. Although. dried. BNC. membranes. are. known. to.
display.a.much.lower.water.absorption.performance.and.swelling.ratio.than.
the.never-dried.ones,.they.are.superior.in.terms.of.convenience,.stability,.and.
portability.. The. freeze-dried. silver. nanoparticle-impregnated. membranes.
fabricated.by.Maneerung.et.al..(2008).displayed.high.swelling.ability,.as.they.
absorbed.62.25.times.their.own.weight.in.water.after.immersion.in.deionized.
water.for.4.h..This.high.swelling.ratio.provides.evidence.that.the.freeze-dried.
bacterial.cellulose.maintains.its.porous.3D.structure.and.can.suck.the.molecules.of.water.into.capillaries.within.the.network.of.nanofibers.more.easily.