Biomedical Engineering Reference
In-Depth Information
8.2 Preparation of Nanoparticle Suspension
One of the most serious problems scientists face about
in vitro
nanotoxicol-
ogy studies is that nanoparticles are not stable in the culture medium and are
easily agglomerated. Thus, most of the nanoparticles are usually no longer
in the nanosize when they reach the target cells. Nonetheless, the microen-
vironment where the cell reacts with the agglomerate should be the surface
of each nanoparticle, and the total surface area of the agglomerate is almost
the same as the sum of the surface area of each single nanoparticle. The cells
recognize the outer surface of a particle. Thus, if the particle is porous, the
outer surface area of the particle is much smaller than the total surface area
measured by the BET (Brunauer-Emmett-Teller) method.
It appears impossible to disperse the particles completely into single par-
ticles at concentrations for the practical
in vitro
toxicology experiments (0.1 μg
mL
-1
to 1 mg mL
-1
). To avoid the production of larger agglomerates,
in vitro
toxicologists use different types of detergents. Table 8.1 shows the detergents
used in
in vitro
nanotoxicology studies with the rationale to use each deter-
gent. The particle suspension is usually sonicated just before addition to the
culture so that the best dispersion is achieved. However, the suspension of
nanoparticles is not stable in the culture medium and the particles may start
to agglomerate before they reach the target cells. Thus, the cellular response
to nanoparticles in the
in vitro
culture system is usually the outcome of com-
plex exposure processes, and the suspended nanoparticles should be charac-
terized when introduced into the culture medium to redefine particle sizes
and shapes.
TABLE 8.1
Detergents Used in
In Vitro
Nanotoxicology
Detergent
Type
Rationale
Serum
Natural
The cells are usually cultured in the
presence of 10% fetal bovine serum
and the serum may not affect the cells
DPPC
(dipalmitoylphosphatidylcholine)
Natural
The alveolar surface is covered with
surfactant and DPPC is a major
component of the lung surfactant
Pluronic F68
Artificial
Nonpyrogenic and “cell culture” type
is commercially available
Tween 20/80
Artificial
Nonionic common detergent in
biochemistry
Humic or fulvic acid
Natural
These are geosolvents and useful for
aquatic toxicology (fish,
Daphnia
)
