Nanoparticles (NP) are introduced in a growing number of commercial products,
including food and beverage, daily use hygiene products such as toothpaste, or
orally-administered drugs. To study the possible toxicity of these nanoparticles, a
model system is the in vitro response of eukaryotic cells to the presence of NP.
However, to understand the observed effects, it is clear that good physical and
chemical characterization of NP, and in particular of their dispersion are needed.
Indeed, the expected effects should be different if the study is dealing with
agglomerates or isolated nanoparticles. For fundamental understanding, it appears
important to work with nanoparticles as well dispersed as possible while being in
relevant biological condition, i.e. cellular culture cell.
In this context, we have studied the dispersion of a very common industrial titania
NP (Degussa P25 produced in ton quantities). When dispersed in water, the suspensions
of NP appear stable for weeks.. When transferred in the cell culture medium (DMEM) or
if directly dispersed in DMEM, strong evolution of size is seen as well as
sedimentation. To address this problem, we have compared different ways, coming from
materials science, of dispersing NP in water with the idea to break in a preliminary
step some of the necks between nanoparticles. The effect of dry ball milling, liquid
ball milling, size of the balls and Ultrasonic dispersion will be compared. The best
results were obtained from high power ultrasonic dispersion. To avoid direct
aggregation, when going to DMEM, a “surfactant” relevant with biological studies
(Foetal Bovine Serum (FBS)) was added in the suspension in order to coat the
nanoparticles prior to transfer in DMEM (or other cell media). The result obtained
with various surfactants and cell media will be presented. It must be noted that our
best results were obtained in the FBS + DMEM medium.