Biomedical Engineering Reference
In-Depth Information
25.5.2 ND as a Protein Delivery Vehicle
NDs.are.of.special.interest.for.the.delivery.of.protein-based.therapeutics..Dahoumane.et.al..
have.combined.diazonium.salt.chemistry.and.atom.transfer.radical.polymerization.(ATRP).
in.the.prospect.of.preparing.hairy.diamond.nanoparticles.(Dahoumane.et.al..2009)..They.
showed.that.by.using.an.electroless.chemical.method,.the.diazonium.salt.can.be.reduced.
at.the.ND's.surface..The.reduced.diazonium.salts.at.the.ND.surface.act.as.macro-initiators.
for. ATRP. and.
tert
-butyl. methacrylate.. The. hairy. NDs. after. hydrolysis. and. 1-ethyl-3-(3-
dimethylaminopropyl). carbodiimide/N-hydroxysuccinimide. (EDC/NHS). coupling. are.
readily.functionalized.with.peptides.or.proteins..The.simple.and.easy.method.of.surface.
modiication.by.using.diazonium.salts,.to.which.various.functional.groups.can.be.attached,.
has.laid.way.for.the.employment.of.NDs.in.numerous.domains.of.science.
Shimkunas. et. al.. (2009). have. explored. the. feasibility. of. using. ND. as. protein. delivery.
vehicles.. In. this. study,. the. authors. demonstrate. the. eficient,. non-covalent. adsorption.
of. insulin. onto. ND's. surface. through. physical. adsorption.. The. insulin. is. released. from.
the. ND-insulin. complex. when. exposed. to. alkaline. environment.. Effective. binding.
and. release. of. insulin. from. NDs. is. further. conirmed. by. using. imaging. methods. and.
adsorption/desorption. assays.. In. addition,. both. MTT. assay. and. RT-PCR. analysis. reveal.
that. the. protein's. function. is. preserved. after. desorption. whereas. the. adsorbed. proteins.
persist. inactive.. It. indicates. that. ND. plays. an. effective. role. in. insulin. delivery.. Nguyen.
et. al.. have. similarly. studied. the. biological. activity. of. ND-conjugated. protein. molecules.
(Nguyen.et.al..2007)..They.observed.that.lysozyme.preserves.its.hydrolytic.activity.after.
its.adsorption.onto.100.nm.NDs..The.relative.hydrolytic.activity.of.ND.adsorbed.lysozyme.
is. 60%. at. pH. 5.. Liu. et. al.. have. also. shown. that. alpha-bungarotoxin,. a. neurotoxin. from.
Bungarus Multicinctus
,.retains.its.bioactivity.by.blocking.membrane.protein.α-7-nicotinic.
acetylcholine. (α-7-nAchR). after. ND. conjugation. (Liu. et. al.. 2008).. The. aforementioned.
studies.clearly.indicate.that.ND.can.serve.as.an.ideal.vehicle.for.protein.delivery.without.
modifying.the.bioactivity.of.conjugated.protein.or.peptides.
25.5.3 ND as a Drug Delivery Vehicle
NDs. hold. several. momentous. properties. like. large. surface-area-to-volume. ratios,. good.
biocompatibility,. and. high. drug-loading. capacity,. which. make. them. an. ideal. choice. for.
drug.delivery..Huang.et.al..have.developed.a.method.of.functionalizing.NDs.(2-8.nm).with.
doxorubicin.(DOX),.a.potent.anti-cancer.drug.(Huang.et.al..2007)..The.interaction.between.
the. negatively. charged. -COO
−
. group. on. ND. and. the. cationic. DOX. ion.
(DOX-NH )
3
+
. are.
direct..Their.results.show.that.the.precipitation.of.DOX.on.ND.is.facilitated.by.the.addi-
tion.of.salts,.such.as.NaCl..Addition.of.NaCl.leads.to.the.increased.Cl
−
.ion.concentration.
in.solution,.which.helps.in.the.formation.of.the.ND-DOX.complexes..Desalination,.on.the.
other.hand,.facilitates.the.effective.release.of.DOX.from.ND..The.complexes.are.eficient.in.
causing.cellular.apoptosis.and.DNA.fragmentation..In.addition,.the.ND.hydrogels.loaded.
with. DOX. are. extremely. capable. of. delivering. the. drugs. into. living. cells. (Figure. 25.12)..
Furthermore,. bioassays. performed. at. cellular. and. genetic. levels. (MTT. assays,. RT-PCR,.
DNA. fragmentation. assays). prove. the. innate. biocompatibility. of. NDs. and. conirm. that.
the.ND-DOX.conjugates.induce.cell.death..The.genes.associated.with.inlammation.such.
as. interleukin-6. (IL-6),. tumor. necrosis. factor-alpha. (TNF-alpha),. inducible. nitric. oxide.
synthases. (NOS),. and. Bcl. X. interacting. domain. do. not. show. any. signiicant. difference.
between. ND-treated. and. control. cells.. These. potential. qualities. make. ND. a. therapeuti-
cally.signiicant.drug.delivery.vehicle.for.both.systemic.and.localized.drug.delivery.
