Biomedical Engineering Reference
In-Depth Information
on.LPS-induced.TNF-α.production.is.observed.after.AO.administration.in.pH-insensitive.
liposomes.(DPPC/DPPG/Chol,.4:1:5)..In.liver.tissue,.the.decreased.production.of.TNF-α.is.
also.associated.with.a.decrease.(35%).in.the.levels.of.TNF-α.mRNA..This.suggests.that.the.
reduced.production.of.TNF-α.is.due.in.part.to.the.oligonucleotide-induced.degradation.of.
mRNA.by.antisense.mechanisms.
Previously,. it. was. also. demonstrated. that. the. i.v.. administration. of. DOPE/OA/Chol.
delivers.a.high.amount.of.intact.AOs.in.the.liver.and.spleen.
67
.Nonetheless,.the.develop-
ment.of.pH-sensitive.formulations.that.are.able.to.avoid.recognition.by.the.RES.is.a.very.
important.challenge.for.the.successful.i.v..administration.of.AOs.or.genes.
For.instance,.anionic.pegylated.complexes.were.prepared.by.adding.anionic.pegylated.
Ph-sensitive. liposomes. (DPPC/(CCTC. or. CHEMS)/Chol-Peg
110
),. where. CCTC. is. a. cho-
lesterol.derivative.bearing.four.carboxylate.moieties.(titrable.anionic.lipids).at.<30.mol%.
lipids,. to. cationic. lipoplexes. (DMAPAP/DOPE. liposomes. +. DNA),. where. DMAPAP. is.
the. cationic. lipid. dimyristylamidocarbamoylmethylaminopropyl-diaminopropylamine,.
which.possesses.two.primary,.one.secondary,.and.one.tertiary.amine.of.low.toxicity.and.
high. reproducibility. as. in. vitro. transfection. agents.
168
. Anionic. pegylated. complexes. do.
aggregate,.and.their.Z.potential.becomes.positive.at.low.pH..The.i.v..administration.of.a.
plasmid. encoding. for. chloramphenicolacetyltransferase. in. anionic. pegylated. complexes.
to.mice-bearing.3LL.tumors.results.in.low.gene.expression.in.the.tumor,.but.CCTC.shows.
a.slightly.higher.level.than.the.CHEMS-containing.formulation..There.is.no.increase.in.
gene. expression. in. the. liver. and. spleen,. or. in. the. lung,. showing. that. anionic. pegylated.
complexes.are.not.retained.in.the.lung.due.to.nonspeciic.interactions,.as.often.observed.
with.cationic.complexes.
20.8.6 Salmonellosis
Gentamicin. (GEN). is. a. hydrosoluble. polycation. aminoglycoside. antibiotic. with. broad-
spectrum. antibacterial. activity.. After. i.v.. or. i.m.. administration,. the. majority. of. GEN.
remains. in. extracellular. locations.. Intracellular. infections,. caused. by. pathogens. such.
as.
Salmonella
(typhoid. fever. and. salmonelosis),.
Listeria
. (meningitis. and. septicemia),. and.
Mycobacterium
.species,.require.that.antibiotics.reach.therapeutic.levels.at.the.intracellular.
site.of.infection..The.in.vitro.eficacy.of.GEN.pH-sensitive.liposomes.(DOPE/N-succinyl-
DOPE,.70:30;.DOPE/N-glutaryl-DOPE,.70:30).containing.small.amounts.of.Peg-ceramide.
C
20
.(0.5.mol;.added.to.reduce.the.aggregation.generated.upon.incorporating.the.polycation.
GEN.to.anionic.liposomes).against.intracellular.infections.is.superior.to.the.eficacies.of.
free. and. GEN. pH-insensitive. liposomes.
169
. The. activity. of. GEN. pH-sensitive. liposomes.
is. similar. against. bacteria. residing. in. phagolysosomes. (
S. typhimurium)
or. in. cytoplasm.
(recombinant.hemolysin-expressing.
S. typhimurium
.strain.and.
L. monocytogenes
)..However,.
correcting.the.values.of.bactericidal.activity.by.substituing.the.activity.of.free.GEN.and.
dividing. by. the. total. nanomols. of. lipids. taken. up. by. 10
6
. cells. renders. a. higher. activity.
for.pH-sensitive.liposomes.(that.is,.higher.on.cytoplasmic.than.on.phagolysosomal.infec-
tions).than.for.pH-insensitive.liposomes..The.addition.of.cholesterol.to.DOPE/N-succinyl-
DOPE/Chol/ceramide-Peg. (35:30:30:5). liposomes. reduces. the. rate. of. drug. release. in.
plasma.upon.administration.to.healthy.mice..In.the.infection.model.of.
Salmonella enterica
serovar.
Typhimurium
infection,.the.pH-sensitive.liposomes.were.more.rapidly.eliminated.
from. blood. than. pH-insensitive. liposomes,. and. both. formulations. increased. the. plasma.
AUC.of.GEN,.compared.to.that.of.free.drug..Liposomal.GEN.was.redirected.to.the.liver.
