Biomedical Engineering Reference
In-Depth Information
different.surface.tensions,.achieved.by.adding.small.amounts.of.Tween.20.(i.e.,.0.001,.0.005,.
and.0.01%),.were.used..Higher.amount.of.Tween.20.caused.a.faster.release.of.protein..To.
improve.the.release.behaviors.of.the.hydrophobic.PLLA.iber.mats,.hydrophilic.polymers.
(i.e.,.poly(ethylene.imine).and.poly(L-lysine)).were.added..With.the.increased.amount.of.
hydrophilic.polymers,.the.hydrophobicity.of.PLLA.iber.mats.decreased.and.the.protein.
release.rate.increased..Hence,.the.release.behaviors.of.the.hydrophobic.PLLA.iber.mats.
were.controlled.by.blending.with.different.amounts.of.hydrophilic.polymers.
76
.Yang.et.al.
77
.
prepared.lysozyme.encapsulated.within.the.core-shell.structure.ibers.by.emulsion-elec-
trospinning..The.lysozyme.was.loaded.in.poly(D-lactic.acid).(PLLA).and.methyl.cellulose.
(MC).solutions.at.concentrations.of.1,.3,.and.5.wt%..The.release.behaviors.of.the.lysozyme.
loaded.in.core-shell.PLLA/MC.iber.mats.were.studied.in.phosphate.buffer.solution.(pH.
7.4). containing. 0.02%. sodium. azide. as. a. bacteriostatic. agent.. The. release. kinetics. for. all.
the. iber. mats. could. be. shown. in. two. stages:. an. initial. fast. release. followed. by. a. con-
stant.linear.release..An.increase.of.lysozyme.loading.caused.a.higher.amount.of.lysozyme.
release.. Thus,. the. core-shell-structured. ibers. could. reduce. the. initial. burst. release,. sus-
tain.the.release.period.dependent.on.the.protein.loading.amount,.and.protect.the.struc-
tural.integrity.and.bioactivity.of.encapsulated.lysozyme.during.incubation.in.medium.
77
.
Rhodamine.B.and.BSA.were.successfully.loaded.into.the.poly(L-lactide-co-carpolactone).
(PLLACL).iber.mats.by.emulsion-electrospinning.
8
.The.release.characteristics.of.the.BSA.
and.rhodamine.B.from.these.iber.mats.were.studied.by.immersion.in.phosphate.buffered.
saline.(pH.7.4).for.various.time.points..The.results.showed.that.the.release.characteristics.
of.rhodamine.B.and.BSA.were.inluenced.and.varied.by.their.incorporated.types..When.
these.drugs.were.incorporated.in.the.core.of.ibers,.the.release.proile.was.sustained..On.
the.other.hand,.when.these.drugs.were.located.in.the.surface.of.ibers,.there.was.a.burst.
release.in.the.beginning.
78
23.3.2 Herbal Substances
There. has. been. much. interest. in. the. electrospinning. process. for. use. in. drug. delivery.
systems. for. over. 10. years.. In. recent. years,. the. use. of. electrospun. iber. mats. as. a. carrier.
for. herbal. substances. has. attracted. a. great. deal. of. attention. due. to. their. ability. to. pro-
duce.ultra-ine.ibers.with.diameters.in.the.range.of.nanometers.to.submicrometers.that.
exhibit.a.high.surface.area-to-volume.or.mass.ratio.
9
.Moreover,.the.use.of.synthetic.drugs.
in.clinical.treatments.of.some.diseases.has.limitations.in.developing.countries.due.to.their.
accessibility.and.relatively.high.cost..Hence,.the.use.of.herbal.substances.has.been.given.
attention.as.alternative.treatments.in.these.countries.
Raspberry.ketone.(RK).is.a.major.aromatic.compound.of.red.raspberry.(
Rubus idaeus
)..
It. is. composed. of. an. abundance. of. sugars,. vitamins,. minerals,. and. polyphenols,. and. is.
widely.used.in.cosmetics.and.foodstuffs..In.addition,.it.has.whitening.and.anti-inlamma-
tion.properties.
80
.Yang.et.al.
79
.investigated.the.use.of.gelatin/PVA.nanoibers.as.carriers.for.
controlled.release.of.RK..They.studied.the.effect.of.the.amount.of.RK.loading.(i.e.,.2.and.
5 wt%),.the.pH.of.releasing.media.(i.e.,.1,.4.8,.and.7),.the.cross-linking.time.(i.e.,.0,.2,.and.
5 h),.and.the.gelatin/PVA.ratio.(i.e.,.10/0,.7/3,.5/5,.3/7,.1/9,.and.0/10).on.the.releasing.charac-
teristic..RK-loaded.gelatin/PVA.iber.mats.could.be.easily.dissolved.in.aqueous.solutions.
due. to. all. of. the. water-soluble. molecules.. However,. this. property. made. them. exhibit. a.
high.initial.burst.release.at.short.times,.and.it.reached.a.plateau.after.2.h..The.percentage.
of.release.of.RK.in.a.buffer.solution.of.pH.1.was.higher.than.those.in.buffer.solutions.of.pH.
4.8.and.7..This.could.be.from.the.protonation.of.amino.groups.of.gelatin.causing.positive.
charges.on.the.polymer..Thus,.the.positive.charges.made.molecular.chains.repulse.each.
