Biomedical Engineering Reference
In-Depth Information
In.terms.of.temperature,.when.Amin.and.co-workers
20
.synthesized.a.TiO
2
-Ag.nanocom-
posite.by.the.sol-gel.method.and.investigated.its.antibacterial.activity.against.
E. coli
,.they.
showed.that.a.nanocomposite.sample.calcined.at.300°C.was.ideal.to.reach.the.maximum.
E.
coli
.inhibition.growth..The.calcined.TiO
2
-Ag.powder.at.300°C.was.able.to.inhibit.bacterial.
growth.even.in.the.absence.of.UV.irradiation;.however,.this.antibacterial.activity.was.not.
observed.for.the.amorphous.sample.and.the.sample.calcined.at.500°C.
Kangwansupamonkon.and.co-workers
21
.investigated.the.nontoxicity.to.humans.of.apa-
tite-coated.TiO
2
.against.four.types.of.bacteria.(
S. aureus
,.
E. coli
,.methicillin-resistant.
S. aureus
(MRSA),.and.
M. luteus
)..The.cotton.fabrics.coated.with.apatite-coated.TiO
2
.by.the.dip.coating.
technique.were.shown.to.be.nontoxic.to.normal.human.dermal.ibroblasts.and.had.an.anti-
microbial.effect,.which.inhibited.the.growth.of.contaminating.microorganisms.
18.2.3 Other Metallic Oxides: ZnO, MgO, CaO, and CeO
2
Other. metallic. oxides,. such. as. ZnO,. MgO,. CaO,. and. CeO
2
,. also. exhibited. antibacterial.
activity.
22-26
.Antibacterial. activities. of. ZnO,. MgO,. and. CaO. powders. with. mean. particle.
sizes.of.2.6,.3.7,.and.2.7.μm,.respectively,.against.
S. aureus
and.
E. coli
.were.quantitatively.
evaluated. by. measuring. the. change. in. electrical. conductivity. of. the. growth. medium.
caused.by.bacterial.metabolism.
25
.CaO.was.the.most.effective.against.
E. coli
,.followed.by.
MgO. and. ZnO.. On. the. other. hand,. ZnO. was. the. most. effective. against.
S. aureus.
. It. has.
been.shown.that.the.antibacterial.activity.of.MgO.nanoparticles.increases.with.decreasing.
particle.size.
26
When. Zhang. et. al.
27,28
. investigated. the. antibacterial. behavior. of. suspensions. of. ZnO.
nanoparticles. (ZnO. nanoluids). against.
E. coli
,. they. found. that. the. antibacterial. activity.
increased. with. increasing. particle. concentration,. as. well. as. increased. with. decreasing.
particle.size..The.use.of.dispersants.(polyethylene.glycol.(PEG).and.polyvinlypyrolidone.
(PVP)).did.not.affect.the.antibacterial.activity.of.ZnO.nanoluids,.but.instead.enhanced.the.
stability.of.the.suspensions..SEM.analyses.of.the.bacteria.before.and.after.treatment.with.
ZnO.nanoluids.showed.that.the.presence.of.ZnO.nanoparticles.damaged.the.membrane.
wall.of.the.bacteria..In.another,.similar.investigation.by.Tam.and.co-workers
29
.on.the.anti-
bacterial.activity.of.ZnO.nanorods.prepared.by.a.hydrothermal.method,.it.was.also.found.
that.ZnO.nanorods.showed.good.activity.against.a.Gram-negative.bacteria.
E. coli
.and.a.
Gram-positive.bacteria.
B. atrophaeus
.
Sustainability.in.antimicrobial.activity.was.evaluated.using.a.colony.count.method.with.
E. coli
.bacteria.on.a.nutrient.agar.medium.(36°C/24.h).in.a.Na-P-buffer.solution.
30
.The.posi-
tively.charged.CeO
2
.nanoparticles.at.neutral.pH.were.tested.on.
E. coli
.
31
.The.nanoparticles.
displayed.a.strong.electrostatic.attraction.toward.bacterial.outer.membranes..Nano-MgO.
crystallites.with.different.particle.sizes.prepared.using.four.different.methods.under.con-
trolled.reaction.conditions
32
.were.active.even.in.the.absence.of.irradication..They.particu-
larly.showed.excellent.bactericidal.activity.against.
S. aureus
.ATCC.6538,.and.their.eficiency.
against.
B. subtilis
ATCC.9372.increased.with.decreasing.size.of.MgO.nanoparticles.
Antimicrobial. activities. have. also. been. tested. on. CaO. nanoparticles. in. Gram-positive.
and.Gram-negative.bacteria.by.the.paper.disc.method..These.calcium.oxide.nanoparticles.
were.synthesized.by.the.thermal.decomposition.process.using.calcium.nitrate.and.sodium.
hydroxide.as.starting.materials.and.ethylene.glycol.as.a.medium.
33
.Synthesized.CaO.nano-
particles.in.toluene.can.inhibit.the.growth.of.three.kinds.of.bacteria:.
E. coli, S. aureus
,.and.
S. epidermidis
..Table 18.1.shows.the.effect.of.calcium.oxide.nanoparticles.on.the.bacteria..
The.inhibition.zone.was.deined.as.the.distance.from.the.rim.of.the.ilter.paper.to.the.edge.
