Optimized dispersion of nanoparticles for biological in vitro and in vivo studies

Background: The aim of this study was to establish and validate a
practical method to disperse nanoparticles in physiological
solutions for biological in vitro and in vivo studies. Results:
TiO(2) (rutile) dispersions were prepared in distilled water, PBS,
or RPMI 1640 cell culture medium. Different ultrasound energies,
various dispersion stabilizers (human, bovine, and mouse serum
albumin, Tween 80, and mouse serum), various concentrations of
stabilizers, and different sequences of preparation steps were
applied. The size distribution of dispersed nanoparticles was
analyzed by dynamic light scattering and zeta potential was
measured using phase analysis light scattering. Nanoparticle size
was also verified by transmission electron microscopy. A specific
ultrasound energy of 4.2 x 10(5) kJ/m(3) was sufficient to
disaggregate TiO(2) (rutile) nanoparticles, whereas higher energy
input did not further improve size reduction. The optimal sequence
was first to sonicate the nanoparticles in water, then to add
dispersion stabilizers, and finally to add buffered salt solution
to the dispersion. The formation of coarse TiO(2) (rutile)
agglomerates in PBS or RPMI was prevented by addition of 1.5 mg/ml
of human, bovine or mouse serum albumin, or mouse serum. The
required concentration of albumin to stabilize the nanoparticle
dispersion depended on the concentration of the nanoparticles in
the dispersion. TiO(2) (rutile) particle dispersions at a
concentration lower than 0.2 mg/ml could be stabilized by the
addition of 1.5 mg/ml albumin. TiO(2) (rutile) particle dispersions
prepared by this method were stable for up to at least 1 week. This
method was suitable for preparing dispersions without coarse
agglomerates (average diameter < 290 nm) from nanosized TiO(2)
(rutile), ZnO, Ag, SiO(x), SWNT, MWNT, and diesel SRM2975
particulate matter. Conclusion: The optimized dispersion method
presented here appears to be effective and practicable for
preparing dispersions of nanoparticles in physiological solutions
without creating coarse agglomerates.