96
A. Antony and J.-H. Boo
c. Functionalization: This is done for improving interfacial interactions such as
by following click chemistry [55, 56], which provides potential high-efficiency
quantitative functionalization with less energy consumption. The click chemistry
follows synthesis of surface functionalization of MONMs using the pre-designed
ligands whose structures contain the following features: (a) a strong anchor (for
example, phosphonic acid or carboxylic acid) that can easily bind with MONMs
surfaces, (b) surface functional groups (contain any number of carbon chains) that
act as spacers or branches from the anchors located on the metal oxide surface,
and (c) attachment of a functional perimeter (for example azide or alkyne groups)
to the spacers to induce orthogonal functionality.
d. Purification-to minimize heterogeneity: This involves removal of excess ligands,
contaminants, and other products formed through the steps (a–c) mentioned
above. Precipitation and re-suspension, density-gradient ultracentrifugation, gel
and size exclusion chromatography, and electrophoresis (such as agarose gel
and free flow) and filtration (such as dia-filtration and nanofiber membranes) are
routinely used purification methods.
e. Characterization: It gives information for regulation or quality control. This is
generally done to obtain sufficient information about a product at a reasonable
cost. The characterization techniques are vast and need to be chosen based on
the specific application needs.
f. Integration-ultimate use of MONMs in products: The integration of MONMs
into materials or devices requires common criteria for spatial control and
product complexity. For instance, colloidal nanoparticles require higher electronic mobility in solution. Similarly, each biomedical application demands
specific integration methods.
8 Risk Assessment
The risk assessment for any MONMs is performed in three steps [37]. Those are (a)
assessment based on exposure which includes frequency, magnitude, and population
duration, (b) assessment based on hazard such as NMs dose response in tissues,
cells, and organs and (c) quantification of final risk due to likelihood of hazard and
exposure. The in vitro and in vivo assay tests using bacterial cultures and animal
studies would provide the cytotoxic mechanism, redox potentials of appropriate
intercellular reactions, levels of cell oxidation etc.
The heavy exposure of MONMs leads to deposition and agglomeration in the
parts of the body and further distributes across blood brain barrier, gut epithelium
or skin. The ultra-fine particles are known to induce cardiovascular effects, fibrosis,
lung cancer, neurodegenerative and teratogenic effects. For example, high administration of TiO 2 NMs in mice has caused morphological changes in the cerebral cortex
neurons and changes in gene expression. The copper and iron oxides also have shown
induced changes in the neurotransmitter secretion and accumulation of NMs in the
brain. The MONMs containing products in suspended liquids or as aerosols cause
A. Antony and J.-H. Boo
c. Functionalization: This is done for improving interfacial interactions such as
by following click chemistry [55, 56], which provides potential high-efficiency
quantitative functionalization with less energy consumption. The click chemistry
follows synthesis of surface functionalization of MONMs using the pre-designed
ligands whose structures contain the following features: (a) a strong anchor (for
example, phosphonic acid or carboxylic acid) that can easily bind with MONMs
surfaces, (b) surface functional groups (contain any number of carbon chains) that
act as spacers or branches from the anchors located on the metal oxide surface,
and (c) attachment of a functional perimeter (for example azide or alkyne groups)
to the spacers to induce orthogonal functionality.
d. Purification-to minimize heterogeneity: This involves removal of excess ligands,
contaminants, and other products formed through the steps (a–c) mentioned
above. Precipitation and re-suspension, density-gradient ultracentrifugation, gel
and size exclusion chromatography, and electrophoresis (such as agarose gel
and free flow) and filtration (such as dia-filtration and nanofiber membranes) are
routinely used purification methods.
e. Characterization: It gives information for regulation or quality control. This is
generally done to obtain sufficient information about a product at a reasonable
cost. The characterization techniques are vast and need to be chosen based on
the specific application needs.
f. Integration-ultimate use of MONMs in products: The integration of MONMs
into materials or devices requires common criteria for spatial control and
product complexity. For instance, colloidal nanoparticles require higher electronic mobility in solution. Similarly, each biomedical application demands
specific integration methods.
8 Risk Assessment
The risk assessment for any MONMs is performed in three steps [37]. Those are (a)
assessment based on exposure which includes frequency, magnitude, and population
duration, (b) assessment based on hazard such as NMs dose response in tissues,
cells, and organs and (c) quantification of final risk due to likelihood of hazard and
exposure. The in vitro and in vivo assay tests using bacterial cultures and animal
studies would provide the cytotoxic mechanism, redox potentials of appropriate
intercellular reactions, levels of cell oxidation etc.
The heavy exposure of MONMs leads to deposition and agglomeration in the
parts of the body and further distributes across blood brain barrier, gut epithelium
or skin. The ultra-fine particles are known to induce cardiovascular effects, fibrosis,
lung cancer, neurodegenerative and teratogenic effects. For example, high administration of TiO 2 NMs in mice has caused morphological changes in the cerebral cortex
neurons and changes in gene expression. The copper and iron oxides also have shown
induced changes in the neurotransmitter secretion and accumulation of NMs in the
brain. The MONMs containing products in suspended liquids or as aerosols cause