Biomedical Engineering Reference
In-Depth Information
8.2.1.3 Fungi
A number of dif erent genera of fungi have been investigated for the
synthesis of metal nanoparticles and it has been found that fungi are
extremely good candidates. In addition to good monodispersity, nanopar-
ticles with well-dei ned dimensions can be obtained by using fungi. h is
was i rst proven by Mukherjee
et al.
[92], where bioreduction of aqueous
Aucl
4
-
was carried out using the fungus
Verticillium
species that led to
the formation of gold nanoparticles with fairly well-dei ned dimension
and good monodispersity. In another study, several
Fusarium oxyspo-
rum
strains were used to produce extracellular silver metal nanoparticles
in the range of 20-50 nm [87]. h rough the UV-Visible, l uorescence
and enzymatic activity analysis, it was verii ed that the reduction of the
metal ion occurred by a nitrate-dependent reductase and an extracel-
lular shuttle quinone [64, 93]. Kumar
et al.
[67] produced
in vitro
sil-
ver nanoparticles (10-25 nm) stabilized by a capping peptide using the
enzyme nitrate reductase purii ed from
Fusarium oxysporum
, phytoche-
latinin, and 4-hydroxyquinoline in the presence of cofactor (NADPH).
Das
et al.
[77] reported extracellular synthesis of gold nanoparticles
using
Rhizopus oryzae
and characterized the particles by FTIR. Riddin
et al.
[94] have reported the biosynthesis of platinum nanoparticles from
the fungus
Fusarium oxysporum
. h e nanoparticles were around 100-180
nm. h e fungi
Verticillium
sp.,
Fusarium oxysporum
sp. and
Aspergillus
l avus
have shown the capability of the nanoparticles production either
extracellularly or intracellularly [66, 95]. h e fungi
Aspergillus l avus,
Aspergillus funigatus
and
Phanerochaete chrysoparium
as well as white rot
fungus
Coriolus versicolar
[96] produce stable silver nanoparticles when
challenged with silver nitrate in aqueous medium. h e shit from bacte-
ria to fungi as a means of developing natural nanofactories has the added
advantage that downstream processing and handling of biomass would
be much simpler [97].
Although nanoparticles synthesized by microorganisms are very stable,
there are drawbacks to microbial synthesis. A major problem is the dii culty
in providing good control over size distribution, shape, and crystallinity of
nanoparticles and the rates at which they are synthesized. h e manipula-
tion of reaction parameters such as pH and temperature might inactivate
the microbes and hinder the bioreduction process. Specialized facilities
and long incubation are required for maintaining the growth of microor-
ganisms and subsequent formation of nanoparticles. Understanding the
mechanism by which the nanoparticles are synthesized by these microbes
at the cellular, biochemical and molecular level may provide informa-
tion on how to improve the rate of synthesis, and the quality and intrinsic
