Biomedical Engineering Reference
In-Depth Information
provides. various. advantages,. such. as. improved. therapeutic. effect,. reduced. toxicity,. and.
handling. ease.. Zeng. et. al.
45,46
. investigated. the. potential. to. use. electrospun. poly(L-lactic.
acid).(PLLA).iber.mats.as.drug.carriers..Various.types.of.drugs,.including.rifampin.(a.drug.
for.tuberculosis),.paclitaxel.(an.anticancer.drug),.and.doxorubicin.hydrochloride.(an.anti-
cancer.drug),.were.loaded.in.the.iber.mat..The.release.characteristics.of.drug-loaded.PLLA.
iber. mats. were. studied. by. immersion. of. these. mats. in. 0.05. M. Tris-HCl. buffer. solution.
containing.proteinase.K.at.37°C..Burst.release.of.the.drugs.was.not.observed,.implying.per-
fect.incorporation.of.drugs.inside.the.ibers..In.the.presence.of.proteinase.K,.PLLA.could.be.
degraded.and.the.drugs.were.subsequently.released..In.this.case,.the.release.was.merely.
attributed.to.the.PLLA.degradation,.not.to.the.diffusion.or.permeation.of.drugs.through.
the.PLLA.carrier.
45
.In.Zeng.et.al.'s.recent.work,
46
.the.inluence.of.solubility.and.the.compat-
ibility.of.drugs.in.the.drug-polymer.system.were.studied..The.results.showed.that.there.
was. good. compatibility. of. paclitaxel. and. doxorubicin. with. PLLA,. whereas. doxorubicin.
hydrochloride.was.found.on.the.surface.of.PLLA.ibers,.which.resulted.in.the.burst.release.
of.doxorubicin.hydrochloride..The.compatibility.of.the.drugs.in.the.drug-polymer.system.
was.found.to.be.an.important.factor.for.controlled.release.in.the.drug.delivery.system.
The.molecular.weight.of.the.polymer.used.to.fabricate.electrospun.matrices.is.another.
important.factor.affecting.the.release.mechanism.of.the.loaded.drugs..Xu.et.al.
47
.devel-
oped. PEG-PLLA. diblock. copolymer. iber. mats. for. the. controlled. release. of. 1,3-bis(2-
chloroethyl)-1-nitrosourea.(BCNU).at.loading.concentrations.of.5-20.wt%..The.release.of.
BCNU.from.the.iber.mats.was.investigated.in.phosphate.buffered.saline.(PBS;.pH.7.4).at.
37°C..The.burst.release.was.found.within.30.min,.and.the.release.rate.of.BCNU.increased.
with. the. amount. of. BCNU. loaded.. The. release. proile. of. BCNU. from. the. electrospun.
PEG-PLLA.iber.mats.was.mainly.controlled.by.the.diffusion.mechanism,.and.not.by.deg-
radation.of.the.iber.mat..A.combination.of.two.releasing.mechanisms.was.found.in.the.
case.of.electrospun.amphiphilic.PEG-PLLA.containing.doxorubicin.hydrochloride.(Dox).
prepared.via.water-in-oil.emulsion-electrospinning..The.diffusion.mechanism.was.pre-
dominant.in.the.early.stage.of.release,.and.enzymatic.degradation.became.predominant.
subsequently..This.phenomenon.could.be.explained.by.the.encapsulation.of.Dox.inside.
and.was.well.distributed.throughout.the.electrospun.ibers.in.the.case.of.emulsion-elec-
trospinning..Moreover,.well-sustained.release.of.Dox.was.observed.for.emulsion-electro-
spinning,.compared.with.suspension-electrospinning..To.investigate.the.release.kinetics.
of. drugs. incorporated. into. iber. mats,. different. amounts. of. Dox. were. loaded. into. the.
PEG-PLLA.iber.mat..The.higher.content.of.Dox.in.the.emulsion-electrospinning.resulted.
in.a.thinner.core.and.a.thicker.sheath.of.ibers..Thus,.Dox.diffused.more.slowly.through.
the.relatively.thicker.PEG-PLLA.sheath.before.being.released.from.the.ibers..The.release.
behaviors.of.Dox.in.this.system.showed.a.three-stage.diffusion-controlled.mechanism.in.
which.the.release.rate.of.the.irst.stage.was.slower.than.that.of.the.second.stage.due.to.the.
reservoir-type.structure.of.the.ibers.formed.
49
.The.release.behaviors.of.both.hydropho-
bic. and. hydrophilic. drugs,. paclitaxel. (PTX). and. doxorubicin. hydrochloride. (Dox),. were.
affected.by.the.solubility.and.distribution.of.the.drugs.in.the.drug-polymer.system..The.
more.hydrophilic.Dox.was.compared.to.PTX,.the.easier.it.was.to.diffuse.into.buffer.solu-
tion,.leading.to.a.higher.release.rate..Interestingly,.the.release.rate.of.PTX.was.accelerated.
by.released.Dox.from.the.coloaded.iber.mats,.but.the.release.rate.of.Dox.was.not.affected.
by.the.released.PTX.
50
In. 2008,. Ranganath. and. Wang. observed. the. effect. of. structure. and. geometry. on. the.
release. behavior. of. electrospun-loaded. materials.
51
. Electrospun. poly(D,L-lactide-co-gly-
colide).(PLGA)-loaded.paclitaxel.(PTX).was.prepared,.and.the.release.behaviors.of.pacli-
taxel.for.postsurgical.chemotherapy.against.glioma.were.investigated..PLGA.copolymer.
