  Recent nanotoxicity studies revealed that the physico-chemical
characteristics of engineered nanomaterials play an important role in the
interactions with living cells. Here, we report on the toxicity and uptake of
the iron oxide sub-10 nm nanoparticles by NIH/3T3 mouse fibroblasts. Coating
strategies include low-molecular weight ligands (citric acid) and polymers
(poly(acrylic acid), MW = 2000 g mol-1). We find that most particles were
biocompatible, as exposed cells remained 100% viable relative to controls. The
strong uptake shown by the citrate-coated particles is related to the
destabilization of the dispersions in the cell culture medium and their
sedimentation down to the cell membranes.
