Size and Shape Selective Metal Oxide Nanomaterials …
99
11 MONMs as Antibacterial Products and Mechanism
of Action
There are varieties of metal and MONMs have shown antibacterial property [67, 68].
The main external influencing factors are the particle size, shape, crystal structure,
MONMs concentration, surface roughness, surface charge, etc. Internally, the metal
(especially Ag, Au, Ga and composites) nanoparticles show (a) attachment to sulfurcontaining proteins (or phospholipid bilayers) found on the bacterial membrane and
cause pits or damages thus leading to the cell-lysis, (b) attachment to cysteine residues
of NADH dehydrogenase which further inactivate other enzymes thus preventing
respiratory processes, (c) production of reactive oxygen species (ROS) and subsequent DNA damage, (d) binding into cytokines, (e) attachment leading to changes in
the membrane potential and decrement in the ATP level and (f) influencing cell
functions for example cell adhesion, differentiation and spreading, all of which
responsible for antibacterial activity.
Also, for MONMs (such as ZnO, MgO, CuO, Fe 2 O 3 and TiO 2 ), (a) formation
of ROS due to photocatalysis in the presence of UV light, (b) membrane phosphate
group binding and subsequent permeation in dark condition, (c) electrochemical
interaction between MONMs and cell wall leading to disruption and leakage of
metabolites, (d) oxidation of proteins and DNA by ROS were shown (Figs. 4 and 5).
In addition, the most popular antibacterial mechanisms are (a) dissolution of metal
ions from the MONMs and its oxidative damage, (b) release of ROS species and its
membrane damage and (c) the direct contact mechanism which is about rupturing
the cell body due to shape [11, 69].
It has also been reported that in addition to the above mechanism, there are many
factors which are responsible for the antibacterial action by MONMs. Those are
bacterial cell wall interactions (such as Gram-positive or negative), surface charge
of NMs, type, and shape of NMs, dispersion of NMs, size, and release of ions [71].
12 Nanoproducts Regulatory Authorities Around
the World
There are several regulatory agencies or institutions around the globe (the following
information are just examples, but the agencies involved are many) to assess the
safety, company promises, potential risks and uncertainty of nanotech-based products. The Korea food and drug safety (KFDS) with many umbrella institutions [72,
73], The USA’s food and drug administration [74], environmental protection agency
(EPA) and national nanotechnology initiative (NNI), European Commission (Joint
Research Centre [75, 76], and REACH [77]), Nano mission-managed by department
of science and technology of India and various central organizations such as CDRI,
ICMR, NIPER and CFTRI [78], China’s National Nanotechnology Standardization
Technical Committee (NSTC) and the corresponding authorization agencies [79],
99
11 MONMs as Antibacterial Products and Mechanism
of Action
There are varieties of metal and MONMs have shown antibacterial property [67, 68].
The main external influencing factors are the particle size, shape, crystal structure,
MONMs concentration, surface roughness, surface charge, etc. Internally, the metal
(especially Ag, Au, Ga and composites) nanoparticles show (a) attachment to sulfurcontaining proteins (or phospholipid bilayers) found on the bacterial membrane and
cause pits or damages thus leading to the cell-lysis, (b) attachment to cysteine residues
of NADH dehydrogenase which further inactivate other enzymes thus preventing
respiratory processes, (c) production of reactive oxygen species (ROS) and subsequent DNA damage, (d) binding into cytokines, (e) attachment leading to changes in
the membrane potential and decrement in the ATP level and (f) influencing cell
functions for example cell adhesion, differentiation and spreading, all of which
responsible for antibacterial activity.
Also, for MONMs (such as ZnO, MgO, CuO, Fe 2 O 3 and TiO 2 ), (a) formation
of ROS due to photocatalysis in the presence of UV light, (b) membrane phosphate
group binding and subsequent permeation in dark condition, (c) electrochemical
interaction between MONMs and cell wall leading to disruption and leakage of
metabolites, (d) oxidation of proteins and DNA by ROS were shown (Figs. 4 and 5).
In addition, the most popular antibacterial mechanisms are (a) dissolution of metal
ions from the MONMs and its oxidative damage, (b) release of ROS species and its
membrane damage and (c) the direct contact mechanism which is about rupturing
the cell body due to shape [11, 69].
It has also been reported that in addition to the above mechanism, there are many
factors which are responsible for the antibacterial action by MONMs. Those are
bacterial cell wall interactions (such as Gram-positive or negative), surface charge
of NMs, type, and shape of NMs, dispersion of NMs, size, and release of ions [71].
12 Nanoproducts Regulatory Authorities Around
the World
There are several regulatory agencies or institutions around the globe (the following
information are just examples, but the agencies involved are many) to assess the
safety, company promises, potential risks and uncertainty of nanotech-based products. The Korea food and drug safety (KFDS) with many umbrella institutions [72,
73], The USA’s food and drug administration [74], environmental protection agency
(EPA) and national nanotechnology initiative (NNI), European Commission (Joint
Research Centre [75, 76], and REACH [77]), Nano mission-managed by department
of science and technology of India and various central organizations such as CDRI,
ICMR, NIPER and CFTRI [78], China’s National Nanotechnology Standardization
Technical Committee (NSTC) and the corresponding authorization agencies [79],