Biomedical Engineering Reference
In-Depth Information
A
B
D
C
FIGURE 9.2
TEM. photographs.. (A). Au. nanoparticles. formed. with.
Trichothecium
sp.. (From. Ahmad,. A.,. et. al.,.
J. Biomed.
Nanotechnol.,
. 1,. 47,. 2005.. With. permission). (B). Ag. particles. synthesized. by.
A. fumigatus
.. (From. Bhainsa,. K.C.,.
and. D'Souza,. S.F.,.
Colloids Surf. B Biointerfaces
,. 47,. 160,. 2006.. With. permission). (C). Au. nanoparticles. formed.
after. exposing. cell-free. extract. from.
Verticillium luteoalbum
to. AuCl
4
−
.. (From. Gericke,. M.,. and. Pinches,. A.,.
Hydrometallurgy
,.83,.132,.2006..With.permission).(D).Pt.nanoparticles.formed.with.
Fusarium oxysporum
..(From.
Riddin,.T.L.,.et.al.,.
Nanotechnology
,.17,.3482,.2006..With.permission.)
of.nanoparticles,.since.fungi.are.known.to.secrete.much.higher.amounts.of.proteins.and.
could.potentially.produce.nanoparticles.at.a.higher.rate.
Further. screening. showed. that.
Fusarium oxysporum
behaved. very. differently. when.
exposed.to.gold.and.silver.ions..The.reduction.of.the.metal.ions.occurred.extracellularly,.
resulting.in.the.formation.of.stable.gold.and.silver.nanoparticles.of.20-50.nm,.an.advan-
tage.from.a.downstream.point.of.view.
34
.During.intracellular.nanoparticle.formation,.an.
additional.process.step.is.needed.to.release.the.nanoparticles.from.the.biomass,.whereas.
extracellular.synthesis.results.in.a.much.cheaper.and.simpler.process.
9
Much. attention. has. therefore. been. focused. on. the. development. of. processes. for. the.
extracellular.production.of.nanoparticles,.and.a.number.of.reports.describing.the.success-
ful.synthesis.of.extracellular.nanoparticles.can.be.found.in.the.literature..Ahmad.et.al.
35
.
found.that.the.fungus.
Trichothecium
.sp..can.synthesize.gold.nanoparticles.of.different.mor-
phologies,.both.intra-.and.extracellularly,.by.changing.its.growing.conditions..Gericke.and.
Pinches
28
. demonstrated. the. formation. of. gold. nanoparticles,. including. triangles,. hexa-
gons,.and.spheres,.when.exposing.cell-free.extracts.obtained.from.
Verticillium luteoalbum
.
to.gold.ions..The.ability.of.
Fusarium oxysporum
to.form.Pt.nanoparticles.with.interesting.
morphologies.was.reported.by.Riddin.et.al.
36
It.was.shown.that.silver.nanoparticles.could.also.be.produced.extracellularly.by.a.num-
ber.of.fungal.species,.including.
Aspergillus lavus
,
37
.
Fusarium semitectum
,
38
.and.
Aspergillus
fumigatis
.
39
.A.few.examples.of.nanoparticles.produced.by.fungi.are.shown.in.Figure 9.2.
