Biomedical Engineering Reference
In-Depth Information
A
B
NUS_CHBE
SEI
5.0 kV
×30,000
100 nm
WD 7.9 mm
NUS_CHBE
SEI
5.0 kV
×45,000
100 nm
WD 7.9 mm
FIGURE 8.1
Field. emission. scanning. electron. microscope. (FESEM). images. of. PLGA. nanoparticles. fabricated. by. (A). the.
solvent.extraction/evaporation.method.and.(B).the.nanoprecipitation.method.
targeting.effects..Current.cancer.therapy.usually.involves.intrusive.processes.to.allow.che-
motherapy.to.shrink.any.cancer.present.or.surgery.to.remove.the.tumor,.if.possible..For.the.
majority.of.patients.with.an.advanced.stage.of.cancer,.treatment.is.limited.to.chemotherapy.
or.radiotherapy..The.purpose.of.chemotherapy.and.radiotherapy.is.to.kill.the.cancer.cells,.
as.these.cells.are.more.susceptible.to.the.actions.of.these.drugs.and.therapies.because.they.
grow.at.a.much.faster.rate.than.healthy.cells..The.effectiveness.of.the.treatment.is.directly.
related. to. the. treatment's. ability. to. target. and. kill. the. cancer. cells. while. affecting. as. few.
healthy.cells.as.possible..Moreover,.the.degree.of.change.in.the.patient's.quality.of.life.and.
eventual.life.expectancy.is.directly.related.to.the.targeting.ability.of.the.treatment. 18,19
Though.there.have.been.several.decades.of.research.and.development,.targeted.delivery.
has.not.yet.fulilled.the.initial.promise.in.the.treatment.of.cancer..The.targeted.delivery.of.
anticancer.drugs.to.solid.tumors.is.a.complicated.issue.because.of.the.impediments.to.drug.
delivery. 20,21 .The.major.impediments.to.drug.delivery.arise.from.tumor.heterogeneity..Cancer.
cells.typically.occupy.less.than.half.of.the.total.tumor.volume,.among.which.approximately.
1.~.10%.are.contributed.by.tumor.vasculature,.and.the.rest.are.occupied.by.a.collagen-rich.
interstitium..The.heterogeneous.distribution.of.blood.vessels,.antigen,.and.receptor.expres-
sion.in.tumors.is.also.a.problem.in.afinity-targeted.delivery.of.drugs.to.solid.tumors. 22,23
The.development.of.a.wide.spectrum.of.nanoscale.technologies.has.tremendous.poten-
tial. to. make. an. important. contribution. in. cancer. imaging,. diagnosis,. treatment,. and.
prevention. 24,25 .These.technological.innovations.have.the.potential.to.turn.molecular.dis-
coveries.arising.from.genomics.and.proteomics.into.widespread.beneit.for.patients..These.
devices.include,.but.are.not.limited.to,.functionalized.carbon.nanotubes,.nanomachines,.
magniiers,.self-assembling.polymeric.nanoconstructs,.nanomembranes,.and.nano-sized.
silicon.chips.for.drug,.protein,.nucleic.acid,.or.peptide.delivery.and.biosensors.and.labora-
tory.diagnostics..In.terms.of.biodegradable.polymeric.nanoparticles,.targeting.ability.can.
be. achieved. by. functionalizing. the. surface. of. drug-loaded. nanoparticles. with. targeting.
ligands,. which. can. then. recognize. and. bind. to. certain. receptors. overexpressed. on. the.
membrane.of.the.cancer.cells.
Targeted.cancer.therapies.interfere.with.cancer.cell.growth.and.division.in.different.ways.
and.at.various.points.during.the.development,.growth,.and.spread.of.cancer..Many.of.these.
therapies. focus. on. proteins. that. are. involved. in. the. signaling. process.. Targeted. molecular.
therapies.target.tumor.antigens.to.alter.the.signaling.either.by.monoclonal.antibodies.(mAbs).
or.by.small.molecule.drugs.that.interfere.with.these.target.proteins..By.blocking.the.signals.
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