present in the migration solution (a silver nanoparticle can be seen
below the flake). Fig. 5c shows spider web-like structures along
with some silver nanoparticles. These structures are possibly due
to the drying of some polymeric material that was dissolved in
the simulant solution during the migration assay. While the polypropylene
containers produce rounded nanoparticles, it seems like
the polyethylene bags release flakes or elongated polymeric
structures. Polyethylene is known to form nanofibres when using
different catalytic systems (Dong etal., 2005, 2006). If these are,
in fact, polypropylene and polyethylene nanoparticles, there is
not available data of their toxicity in nanoparticle form. Neither
of them is acutely toxic in bulk form but they are non-biodegradable
and subsequently not in the FDA-approved list of biodegradable
and biocompatible polymers to be used as drug release
carriers. Cells are known to preferentially internalize nanoparticles
with diameters of 10–100 nm and the particles that we observed
are bigger than 200 nm but nevertheless their toxicity should be
studied