Biomedical Engineering Reference
In-Depth Information
(Jang. et. al.. 2010).. Signiicantly. higher. activity. was. seen. in. the. particles. entrapped. in.
8000.Da.PEG.compared.with.575.Da.PEG,.presumably.due.to.reduced.transport.limitation..
Similarly,.the.K
m
.of.the.GOD.was.increased.slightly.after.the.nanoparticles.were.entrapped.
in. the. 8000.Da. PEG,. but. substantially. after. entrapment. in. the. 575.Da. PEG. hydrogel.. In.
addition,.the.enzyme.stability.was.monitored.for.enzyme.immobilized.to.SNPs,.entrapped.
in.an.8000.Da.PEG.hydrogel,.and.for.the.immobilized.and.entrapped.GOD..The.GOD.that.
was.both.immobilized.and.entrapped.retained.approximately.70%.of.its.original.activity.
over.the.course.of.1.week,.while.the.other.two.preparations.lost.∼80%.of.their.activity.over.
the.same.time.period,.demonstrating.the.advantage.of.simultaneous.immobilization.and.
encapsulation.
In. an. effort. to. reduce. the. diffusional. limitations. that. are. often. seen. upon. enzyme.
encapsulation,. Kim. and. Grate. (2003). reported. single. enzyme. encapsulation. in. a.
porous. composite. organic/inorganic. network. less. than. a. few. nanometers. thick.. These.
single-enzyme. nanoparticles. (SENs). were. synthesized. by. irst. reacting. surface. amino.
groups.with.acryloyl.chloride.to.yield.surface.vinyl.groups..The.modiied.enzyme.was.
solubilized. in. hexane. and. mixed. with. methacryloxypropyltrimethoxysilane. (MAPS),. a.
vinyl.monomer.with.pendant.trimethoxysilane.groups..After.free-radical.initiated.vinyl.
polymerization,.the.products.were.extracted.into.a.cold.aqueous.buffer.solution,.and.then.
aged. at. 4°C. at. least. 3. days. for. silanol. condensation.. While. the. enzyme. in. their. studies.
(chymotrypsin).exhibited.approximately.50%.loss.of.catalytic.activity.(k
cat
),.the.K
m
.value.
was.largely.unchanged,.suggesting.that.there.was.little.to.no.mass.transfer.limitation.for.
the.encapsulated.enzyme..In.addition,.the.catalytic.stability.was.substantially.enhanced.
when. compared. with. the. free. enzyme.. Building. on. the. technology. introduced. by. Kim.
and.Grate,.Gao.et.al..(2009).used.a.similar.approach.to.encapsulate.trypsin.and.then.to.
prepare.monolithic.enzymatic.microreactors.for.peptide.mapping.analysis.of.myoglobin.
and. bovine. serum. albumin. with. MALDI-TOF-MS.. Vinyl. groups. on. the. protein. surface.
were. generated. by. acryloylation.. Then,. the. acryloylated. enzyme. was. encapsulated. into.
polyacrylates.by.free-radical.copolymerization.with.acrylamide.as.the.monomer.and.
N
,.
N
-methylenebisacrylamide.as.the.cross-linker,.and.inally,.the.polymers.were.immobilized.
onto.the.activated.inner.wall.of.capillaries.via.the.reaction.of.the.vinyl.groups..They.were.
able. to. achieve. high. enzyme. loadings. and. found. the. enzyme. in. the. reactors. had. good.
stability. in. the. presence. of. organic. solvents. and. rapid. digestion. eficiency. due. to. very.
little.mass.transfer.limitation.
In. a. very. timely. application. of. polymer-hydrogel. encapsulation. of. enzymes,.
polyethyleneimine.(PEI)-dextran.sulfate.(DS).polyelectrolyte.complexes.were.used.to.entrap.
pectinase,.an.enzyme.employed.to.clean.up.fracturing.luid.used.in.hydraulic.fracturing.
to. improve. oil. and. natural. gas. production. (Barati. et. al.. 2011).. Using. an. encapsulation.
method. originally. developed. for. drug. delivery. applications,. they. hypothesized. that.
this. nanoparticle. system. would. also. be. capable. of. entrapping. and. releasing. pectinase.
in. a. controlled. manner.. They. then. envisioned. that. the. pectinase. nanoparticles. could. be.
mixed.with.the.high.viscosity.fracturing.luid.(which.typically.contains.guar.gum).before.
injection,.and.the.luid.would.break.down.at.an.appropriate.rate..They.explored.a.variety.
of.concentration.of.PEI,.DS,.and.pectinase.as.well.as.the.order.of.addition.to.optimize.the.
system..Depending.on.the.concentrations,.particle.sizes.ranged.from.∼200.to.500.nm..The.
reproducibility.of.particle.size.was.very.good.and.the.particles.showed.good.stability.over.
time.. When. the. nanoparticles. of. varying. compositions. were. mixed. with. the. guar. gum.
solution,.nanoparticles.with.a.2:1.ratio.of.PEI.to.DS.showed.the.best.controlled.release.of.
enzyme.over.time;.however,.all.the.nanoparticle-containing.solutions.showed.equivalent.
