10
T. K. Barik et al.
5.1 Toxicity of Nanomaterials
Greater human exposure of nanomaterials presents in the environment; more significant is the harmful effect on human health. The assessment of the cytotoxicity of
nanomaterials assists in the proper elucidation of the biological activity. Gerloff et al.
reported the cytotoxicity of various nanoparticles, such as zinc oxide (ZnO), SiO 2 , and
TiO 2 , on human Caco-2 cells [113]. Shen et al. [114] showed the human immune cells
are prone to toxicity due to ZnO nanoparticles [115]. The ZnO nanoparticles damage
mitochondrial and cell membranes in rat kidney, ultimately leading to nephrotoxicity
[115]. Generally, the nanomaterial toxicity mechanism comprises reactive oxygen
species formation and genotoxicity. However, as described earlier, the toxicity of ZnO
nanoparticles mainly affects immune cells. Various nanomaterials with their diverse
sizes alter mitochondrial function. For example, ZnO nanoparticles generate Zn
2+
ions, which disrupts charge balance in the electron transport chain in the mitochondria and therefore triggers reactive oxygen species generation. Nanosilver particle
has a genotoxic effect. A 20-nm nanosilver has a genotoxic effect on human liver
HepG2 and colon Caco2 cells. It has also increased mitochondrial injury and the loss
of double-stranded DNA helix in both cell types [116]. Inhalation of TiO 2 nanoparticles resulted in pulmonary overload in rats and mice with inflammation [117, 118].
The cytotoxic and genotoxic effects of TiO 2 nanoparticles on the human lung were
reported by Jugan et al. [119]. TiO 2 nanoparticles are genotoxic, and it can induce
pathological damage of the liver, kidney, spleen, and brain. Du et al. reported cardiovascular toxicity of silica nanoparticles in rats [120]. The surface coating of quantum
dots causes toxicity to the skin cells, including cytotoxicity and immunotoxicity
[121]. Nanosilver is used in wound dressings, affects both keratinocytes and fibroblasts. Fibroblasts show higher sensitivity towards nanosilver than by keratinocytes.
Again, iron oxide nanoparticles rapidly get endocytosis on cultured human fibroblasts and interrupt the function. Citrate/gold nanoparticles have shown toxicity on
human dermal fibroblasts [122]. Carbon nanotubes have high toxicity and produce
harmful effects on humans. The nanoparticles can penetrate the lungs, then reached
the blood and acted as a barrier for the circulation of blood into the brain. They
can also enter inside other organs like bone marrow, lymph nodes, spleen, or heart.
Sometimes, nanoparticles can incite inflammation, oxidant and antioxidant activities, oxidative stress, and change in mitochondrial distribution. These effects depend
on the type of nanoparticles and their concentrations [101]. Copper nanoparticles
(diameters 40 nm and 60 nm) harm brain cells at low concentrations. It activated the
proliferation of the endothelial cells in brain capillaries. Ag nanoparticles (25, 40,
or 80 nm) influenced the blood-brain barrier, causing a pro-inflammatory reaction,
which might induce a brain inflammation with neurotoxic effects [123]. Smaller Ag
nanoparticles (25 nm and 40 nm diameter) can induce cytotoxic effect at a higher rate
than larger nanoparticles. Nanoparticles also have harmful effects on the brain cell
of the mouse and rat. The high concentration of nanoparticles can affect brain blood
fluxes, with consequent cerebral edema. Pathogenic effects of Ag-nanoparticles (25,
40, and 80 nm diameter), Cu-nanoparticles (40 and 60 nm), and Au-nanoparticles
T. K. Barik et al.
5.1 Toxicity of Nanomaterials
Greater human exposure of nanomaterials presents in the environment; more significant is the harmful effect on human health. The assessment of the cytotoxicity of
nanomaterials assists in the proper elucidation of the biological activity. Gerloff et al.
reported the cytotoxicity of various nanoparticles, such as zinc oxide (ZnO), SiO 2 , and
TiO 2 , on human Caco-2 cells [113]. Shen et al. [114] showed the human immune cells
are prone to toxicity due to ZnO nanoparticles [115]. The ZnO nanoparticles damage
mitochondrial and cell membranes in rat kidney, ultimately leading to nephrotoxicity
[115]. Generally, the nanomaterial toxicity mechanism comprises reactive oxygen
species formation and genotoxicity. However, as described earlier, the toxicity of ZnO
nanoparticles mainly affects immune cells. Various nanomaterials with their diverse
sizes alter mitochondrial function. For example, ZnO nanoparticles generate Zn
2+
ions, which disrupts charge balance in the electron transport chain in the mitochondria and therefore triggers reactive oxygen species generation. Nanosilver particle
has a genotoxic effect. A 20-nm nanosilver has a genotoxic effect on human liver
HepG2 and colon Caco2 cells. It has also increased mitochondrial injury and the loss
of double-stranded DNA helix in both cell types [116]. Inhalation of TiO 2 nanoparticles resulted in pulmonary overload in rats and mice with inflammation [117, 118].
The cytotoxic and genotoxic effects of TiO 2 nanoparticles on the human lung were
reported by Jugan et al. [119]. TiO 2 nanoparticles are genotoxic, and it can induce
pathological damage of the liver, kidney, spleen, and brain. Du et al. reported cardiovascular toxicity of silica nanoparticles in rats [120]. The surface coating of quantum
dots causes toxicity to the skin cells, including cytotoxicity and immunotoxicity
[121]. Nanosilver is used in wound dressings, affects both keratinocytes and fibroblasts. Fibroblasts show higher sensitivity towards nanosilver than by keratinocytes.
Again, iron oxide nanoparticles rapidly get endocytosis on cultured human fibroblasts and interrupt the function. Citrate/gold nanoparticles have shown toxicity on
human dermal fibroblasts [122]. Carbon nanotubes have high toxicity and produce
harmful effects on humans. The nanoparticles can penetrate the lungs, then reached
the blood and acted as a barrier for the circulation of blood into the brain. They
can also enter inside other organs like bone marrow, lymph nodes, spleen, or heart.
Sometimes, nanoparticles can incite inflammation, oxidant and antioxidant activities, oxidative stress, and change in mitochondrial distribution. These effects depend
on the type of nanoparticles and their concentrations [101]. Copper nanoparticles
(diameters 40 nm and 60 nm) harm brain cells at low concentrations. It activated the
proliferation of the endothelial cells in brain capillaries. Ag nanoparticles (25, 40,
or 80 nm) influenced the blood-brain barrier, causing a pro-inflammatory reaction,
which might induce a brain inflammation with neurotoxic effects [123]. Smaller Ag
nanoparticles (25 nm and 40 nm diameter) can induce cytotoxic effect at a higher rate
than larger nanoparticles. Nanoparticles also have harmful effects on the brain cell
of the mouse and rat. The high concentration of nanoparticles can affect brain blood
fluxes, with consequent cerebral edema. Pathogenic effects of Ag-nanoparticles (25,
40, and 80 nm diameter), Cu-nanoparticles (40 and 60 nm), and Au-nanoparticles