Agriculture Reference
In-Depth Information
6.3.1
Inorganic Antimicrobial Nanoparticles
Metallic nanoparticles can be used as antimicrobial agents or nanocarriers for active
substances. Silver nanoparticles are known for their antimicrobial activity and have
been used in applications to remove microorganisms in air filters, water, and
medicine. The Ag
+
ions are effective in millimolar concentration while Ag
nanoparticles in the nanomolar range, showing that they are much more effective
in performing antimicrobial activities (Rai et al.
2009
). Among the metallic
nanoparticles, silver is considered the most promising nanomaterial with bacteri-
cidal and viricidal properties due to its wide-range efficacy, relatively low toxicity,
ease of use, charge capacity, high surface to volume ratio, and adaptability to
several substrates. Ag nanoparticles attach to the surface of cell membrane of
these pathogenic bacteria and drastically disturb its proper function like respiration
and permeability. The damage to the cell may be caused by strong interaction with
sulfur- and phosphorous-containing molecules, such as proteins and DNA (Sharma
et al.
2009
; Prabhu and Poulose
2012
). These interactions would prevent DNA or
RNA synthesis, resulting in microbial death.
The potential use of Ag nanoparticles in biomedical applications has been
extensively investigated. For example, the combination of the biocidal properties
of Ag nanoparticles and the bacteriolytic activity of lysozyme was used to produce
a colloidal suspension for coatings of medical instrumentation. These
nanocomposites exhibit antimicrobial activity against several bacteria reducing
the viability of
Acinetobacter baylyi
,
Bacillus anthracis
,
Klebsiella pneumoniae
,
and
Staphylococcus aureus
at least 1.5 log within 3 h (Eby et al.
2009
).
Ag nanoparticles produced extracellularly by
Fusarium oxysporum
can be
incorporated in several types of materials such as textiles. These textiles containing
Ag nanoparticles are sterile and can be useful to prevent infection with pathogenic
bacteria such as
S. aureus
(Dur
ยด
n et al.
2007
). Ag nanoparticles synthesized by
Lecanicillium lecanii
were coated on bleached cotton fabrics, and the antibacterial
activity of these materials was observed against
S. aureus
and
Escherichia coli
(Namasivayam and Avimanyu
2011
). Extracellular synthesis of gold nanoparticles
using
Rhizopus oryzae
was employed for the generation of nanogold bioconjugate
structure. These nanostructures showed strong adsorption capacity and have been
successfully utilized to obtain water free from pathogens and pesticides (Das
et al.
2009
). Silver nanoparticles and metal oxide nanoparticles have been also
described for drinking water purification (Savage and Diallo
2005
).
Although nanoparticles have been extensively studied for drug delivery and
sustained release in biomedical sciences, similar applications in agriculture are
still poorly investigated. Nanoparticle formulations of biopesticides have been
proposed to reach a better spatial distribution of the pesticides on leaf surfaces,
which would result a better efficiency (Liu et al.
2008
). Solid and liquid formula-
tions of silver, aluminum oxide, zinc oxide, and titanium dioxide nanoparticles
were tested for the control of rice weevil and grasserie disease in silkworm (
Bombyx
mori
) caused by
Sitophilus oryzae
and baculovirus BmNPV (
B. mori
nuclear
