Biomedical Engineering Reference
In-Depth Information
nanomaterials like titanium, copper, magnesium or alginate have promising
antibacterial properties, Au and AgNP have showed best efficiency against bacteria,
viruses and fungi (Rai et al. 2009 ). The broad-spectrum antimicrobial properties of
metallic NPs (mostly silver and gold) encourage their use as disinfectants in puri-
fication processes (medicine, water and air), food production, cosmetics, clothing,
and numerous household products (Marambio-Jones and Hoek 2010 ).
In this section, we will illustrate the antibacterial, antiviral and antifungal effects
of biosynthesized NPs. This application promises to be very beneficial for both the
industrial and medical fields. For further reading on AgNPs utilization and silver
mechanism of action, see aforementioned review articles - Marambio-Jones and
Hoek ( 2010 ), Rai et al. ( 2009 ), Nair and Laurencin ( 2007 ) or review papers by
Sharma et al. ( 2009 ), Cho et al. ( 2005 ).
3.4.1
Antibacterial Activity
Bacteria have different membrane and cell wall structures. Therefore, we can classify
them generally as Gram-negative (G−) or Gram-positive (G+). The key component
of the membrane, peptidoglycan, is a decisive factor in the membrane organization.
G− bacteria has only a thin peptidoglycan layer (~2-3 nm) between their two mem-
branes, while G+ bacteria lack the outer membrane (is substituted by thick peptido-
glycan layer).
Morones et al. ( 2005 ) published study regarding possible interactions between
AgNPs and G− bacteria. Small NPs disturb the function of the membrane (such as
permeability or respiration) by attaching to it's surface and, subsequently, penetrate
the cell and cause further damage by interacting with the DNA.
Spectrum of organisms used for biosynthesis of NPs with antibacterial effect
varies from bacteria, fungi and alga to leaf, root, bark and tuber extracts of higher
plants and trees. As one of the first records, Ingle et al. ( 2008 ) reported a mycosyn-
thesis of silver antibacterial NPs with biological activity against different human
pathogens including multidrug resistant and highly pathogenic bacteria such as
Staphylococcus aureus, Salmonella typhi, Staphylococcus epidermidis , and
Escherichia coli . Similarly, fungal strain Aspergillus clavatus was used for extra-
cellular biosynthesis of stable AgNPs with antibacterial activity against methicillin
(antibiotics) resistant Staphylococcus aureus and Staphylococcus epidermidis
(Saravanan and Nanda 2010 ). Antibacterial activity against Staphylococcus aureus
KCCM 12256 was also observed in case of AgNPs biosynthesized by filamentous
mold Aspergillus oryzae (Binupriya et al. 2009 ). Bioreductive synthesis of nano-
sized Ag particles was performed using live and dead cell filtrates with NP size
varying from 5 to 50 nm. Another phytopathogenic fungal specie Bipolaris nodu-
losa can serve as reducing agent for silver nitrate reduction with resulting Ag NPs
active against Bacillus subtilis, Bacillus cereus, Pseudomonas aeruginosa, Proteus
vulgaris, Escherichia coli and Micrococcus luteus pathogens (Saha et al. 2010 ).
Ag NPs biosynthesized by gilled mushroom specie Pleurotus sajor-caju (Nithya
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