Biomedical Engineering Reference
In-Depth Information
There. were. two. base. materials. used. in. this. work:. PLGA,. which. controls. the. degrada-
tion.rate.of.the.material,.and.poly(lactide).(PLA),.which.provides.mechanical.strength.to.
the.material..Moreover,.to.control.the.drug.release.proile,.an.amphiphilic.poly(ethylene.
glycol)-b-poly(lactide). (PEG-b-PLA). diblock. copolymer. was. added. to. the. polymer. solu-
tions. to. encapsulate. the. hydrophilic. drug. (cefoxitin. sodium).. The. addition. of. cefoxitin.
sodium.to.the.polymer.solutions.caused.the.morphology.of.the.iber.to.change.from.bead-
and-string-like. to. ibrous-like.. Interestingly,. the. addition. of. an. amphiphilic. PEG-b-PLA.
block.copolymer.into.the.polymer.reduced.the.amount.of.released.cefoxitin.at.earlier.time.
points.and.extended.the.drug.release.proile.to.longer.times. 30
23.3.1.4   Vitamins
In. 2007,. Taepaiboon. et. al. 64 . prepared. electrospun. cellulose. acetate. (CA). iber. mats. and.
investigated.their.potential.for.use.as.drug.carriers.to.deliver.the.model.vitamins.all-trans.
retinoic.acid.or.vitamin.A.acid.(Retin-A).and.α-tocopherol.or.vitamin.E.(Vit-E)..The.release.
characteristics.of.these.vitamin-loaded.CA.iber.mats.and.ilms.were.studied.by.immer-
sion.in.an.acetate.buffer.solution.containing.either.0.5.vol%.Tween.80.or.a.mixture.of.0.5.
vol%.Tween.80.and.10.vol%.methanol..The.results.showed.that.the.vitamin-loaded.CA.iber.
mats.exhibited.a.gradual.release.over.the.time.periods,.whereas.the.vitamin-loaded.CA.
ilms. exhibited. a. burst. release. of. the. vitamins.. Poly(lactic-co-glycolic. acid). (PLGA). iber.
mats.were.also.used.as.carriers.to.incorporate.all-trans.retinoic.acid.(RA). 65 .Comparisons.
were.made.against.the.PLGA.ilms..The.release.characteristics.were.carried.out.by.immer-
sion.of.these.materials.in.phosphate.buffer.solution.(pH.7.4).at.37°C..The.results.showed.
that.the.release.rate.of.RA.from.the.PLGA.iber.mats.was.sustained.due.to.the.preserved.
ibrous.structure.of.the.PLGA.iber.mats.after.4.months..The.release.rate.of.RA.from.the.
PLGA. ilms,. however,. showed. a. triphasic. release. proile.. This. was. due. to. the. different.
structures.and.degradation.behaviors.of.the.two.drug.delivery.systems. 65
23.3.1.5   Proteins
Zeng.et.al. 66 .prepared.protein-loaded.(bovine.serum.albumin.(BSA).or.luciferase).poly(vinyl.
alcohol).(PVA).iber.mats.by.electrospinning..To.control.the.release.characteristics.of.pro-
tein.from.PVA.iber.mats,.poly( p -xylylene).(PPX).was.coated.to.protein-loaded.iber.mats.
with.different.thicknesses.of.PPX.by.chemical.vapor.deposition.(CVD)..They.found.that.
the. uncoated. PVA. iber. mats. showed. a. burst. release. of. protein.. On. the. other. hand,. the.
PPX-coated.PVA.iber.mats.exhibited.a.signiicantly.retarded.release.of.protein,.depend-
ing.on.the.coating.thickness.of.PPX..Moreover,.the.release.of.luciferase.activity.retained.its.
enzyme.activity.after.electrospinning..Hence,.this.was.the.prerequisite.for.the.application.
of.enzymes.or.other.sensitive.agents.released.from.the.electrospun.iber.mats. 66 .The.encap-
sulation.of.human.β-nerve.growth.factor.(NGF),.which.was.stabilized.in.carrier.protein,.
bovine.serum.albumin.(BSA).in.a.copolymer.of.ε-carpolactone.and.ethyl.ethylene.phos-
phate.(PCLEEP),.was.prepared.by.conventional.electrospinning. 67 .A.sustained.release.of.
NGF.from.PCLEEP.iber.mats.was.obtained.for.up.to.3.months..A.PC12.neurite.outgrowth.
assay.also.conirmed.that.the.bioactivity.of.NGF-loaded.PCLEEP.iber.mats.was.retained.
throughout. the. period. of. sustained. release.. Hence,. these. iber. mats. had. eficiency. for.
use. in. peripheral. nerve. regeneration. applications. 67 . Heparin-loaded. poly(ε-caprolactone).
(PCL).iber.mats.were.also.prepared.by.conventional.electrospinning. 68 .Heparin.is.used.to.
prevent.vascular.smooth.muscle.cell.(VSMC).proliferation,.which.can.lead.to.graft.occlu-
sion. and. failure.. Luong-Van. et. al. 68 . studied. the. effect. of. heparin. incorporation. on. iber.
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