Nanomaterials: An Introduction
11
(3 and 5 nm) on the blood-brain barrier of the pig have been reported [124]. Silver
nanoparticles (45 nm) influenced the acetylcholine activity via nitric oxide generation; it induces hyperactivity of rat tracheal smooth muscle [125]. It is also reported
that Ag- nanoparticles (25 nm) produced oxidative stress after the injection into the
mouse. The nanoparticles were aggregated in the kidneys, lungs, spleen red pulp,
and the nasal airway, with no observable morphological changes apart from the nasal
cavity [126].
Very few cells do not undergo morphological changes after withstanding the airliquid interface culture for an extended duration. Au-nanoparticles (5 nm and 15 nm
diameter) penetrated the mouse fibroblasts, where they remained stocked. Only the
presence of 5 nm Ag-nanoparticles disrupted cytoskeleton resulting in narrowing
and contraction of cells. Many engineered nanomaterials, such as TiO 2 , magnetite
iron, CeO 2 , carbon black, SWCNTs, and MWCNTs, also might cause different levels
of inflammatory reactions, including enhanced pro-inflammatory cytokines expression, target inflammation-related genes, and micro-granulomas formation [127, 128].
The intra-tracheal administration of MWCNTs with variable length and iron content
in hypertensive rats Led to the lung inflammation with increased blood pressure
and lesions in abdominal arteries along with accumulation in multiple organs i.e.,
liver, kidneys, and spleen post seven days and 30 days exposure [129]. Maneewatttanapinyo et al. studied acute toxicity of colloidal silver nanoparticles administered
in laboratory mice and observed no mortality any acute toxicity symptoms after a
limited dose of 5.000 mg/kg post 14 days of oral administration. No differences
could be observed among groups after hematological and biochemical assessment
and the histopathological study. The instillation of silver nanoparticles at the concentration of 5.000 ppm developed a transient eye irritation for 24 h. The application
of these nanomaterials on the skin did not produce any micro or macroscopic toxicity [130]. The schematic mechanism of silver nanoparticle’s toxicity in the human
body is shown in Fig. 3 [131]. The liver and spleen are maximum exposed organs to
nanomaterials owing to the prevalence of phagocytic cells in the reticuloendothelial
system. Also, the organs with high blood flow, such as kidneys and lungs, can be
affected.
5.2 Health Hazards in Human
Despite having many benefits and using nanomaterials, it may cause health hazards
to humans due to a tiny size. The broad absorption surface of the lung, the thinner
air–blood barrier, and comparatively less inactivation of enzymes leads to faster
entry for particles into the systemic blood circulation at higher drug concentrations.
Additionally, intended uptake, exposure of airborne particles from the environment,
and nanoparticles released during the manufacturing process may also cause health
hazards for humans. Usually, nanomaterials’ biological effects are based on their size,
composition, shape, and even on their electronic, magnetic, optical, and mechanical
11
(3 and 5 nm) on the blood-brain barrier of the pig have been reported [124]. Silver
nanoparticles (45 nm) influenced the acetylcholine activity via nitric oxide generation; it induces hyperactivity of rat tracheal smooth muscle [125]. It is also reported
that Ag- nanoparticles (25 nm) produced oxidative stress after the injection into the
mouse. The nanoparticles were aggregated in the kidneys, lungs, spleen red pulp,
and the nasal airway, with no observable morphological changes apart from the nasal
cavity [126].
Very few cells do not undergo morphological changes after withstanding the airliquid interface culture for an extended duration. Au-nanoparticles (5 nm and 15 nm
diameter) penetrated the mouse fibroblasts, where they remained stocked. Only the
presence of 5 nm Ag-nanoparticles disrupted cytoskeleton resulting in narrowing
and contraction of cells. Many engineered nanomaterials, such as TiO 2 , magnetite
iron, CeO 2 , carbon black, SWCNTs, and MWCNTs, also might cause different levels
of inflammatory reactions, including enhanced pro-inflammatory cytokines expression, target inflammation-related genes, and micro-granulomas formation [127, 128].
The intra-tracheal administration of MWCNTs with variable length and iron content
in hypertensive rats Led to the lung inflammation with increased blood pressure
and lesions in abdominal arteries along with accumulation in multiple organs i.e.,
liver, kidneys, and spleen post seven days and 30 days exposure [129]. Maneewatttanapinyo et al. studied acute toxicity of colloidal silver nanoparticles administered
in laboratory mice and observed no mortality any acute toxicity symptoms after a
limited dose of 5.000 mg/kg post 14 days of oral administration. No differences
could be observed among groups after hematological and biochemical assessment
and the histopathological study. The instillation of silver nanoparticles at the concentration of 5.000 ppm developed a transient eye irritation for 24 h. The application
of these nanomaterials on the skin did not produce any micro or macroscopic toxicity [130]. The schematic mechanism of silver nanoparticle’s toxicity in the human
body is shown in Fig. 3 [131]. The liver and spleen are maximum exposed organs to
nanomaterials owing to the prevalence of phagocytic cells in the reticuloendothelial
system. Also, the organs with high blood flow, such as kidneys and lungs, can be
affected.
5.2 Health Hazards in Human
Despite having many benefits and using nanomaterials, it may cause health hazards
to humans due to a tiny size. The broad absorption surface of the lung, the thinner
air–blood barrier, and comparatively less inactivation of enzymes leads to faster
entry for particles into the systemic blood circulation at higher drug concentrations.
Additionally, intended uptake, exposure of airborne particles from the environment,
and nanoparticles released during the manufacturing process may also cause health
hazards for humans. Usually, nanomaterials’ biological effects are based on their size,
composition, shape, and even on their electronic, magnetic, optical, and mechanical