(379a) Nanotoxicity of Complex Engineered Nanomaterials Using 3t3 Fibroblast and Human Embryonic Stem Cell Assays

Functional nanomaterials are developing at an ever accelerating pace and are already finding widespread application in consumer products including cosmetics, clothing, and consumer electronics.  However, increasing evidence indicates that nanomaterials are showing elevated toxicity and there is an urgent need to develop methods that allow sensitive nanotoxicity screening, and the capability to study and connect the nanomaterial properties with toxicity.  3t3 fibroblasts are well suited for in vitro nanotoxicity studies as they are a robust, inexpensive established cell model which is finding increasing use for nanotoxicity studies.  Human embryonic stems cells (hESC), on the other hand, are primary cells that have been shown to closely recapitulate human development. The human relevance of hESC, along with its high sensitivity presents it as a novel in vitromodel for toxicity evaluation.

Porous silica nanomaterials are used in a wide range of applications including biomedical imaging, drug delivery, catalysis, and sensors, as they constitute a versatile, easily modifiable, largely non-toxic template.  We hypothesize that embedding metal nanoparticles in silica could have a significant impact on the nanoparticle toxicity by modifying transport and interaction of the embedded metal NPs within the cell environment, while still providing full access to the metal nanoparticle surface and hence maintain the functionality of the embedded nanoparticle. 

In the present work, three different complex engineered nanomaterials are investigated in cytotoxicity assays, including surface-deposited nickel nanoparticles on silica nanoparticle supports (Ni-on-SiO₂), embedded nickel nanoparticles in silica (non-hollow Ni-SiO₂), and encapsulated nickel nanoparticles in silica (hollow Ni-SiO₂). The cytotoxicity assays are coupled with proliferation assays to determine the toxicity of the nanomaterials in comparison to an inorganic nickel salt (NiCl₂).  The 3t3 fibroblast assays showed elevated toxicity for all three Ni/SiO₂ configurations compared to the equivalent dosing of NiCl_2, with the hollow Ni-SiO₂ and Ni-on-SiO₂ nanomaterials showing higher toxicity than the non-hollow Ni-SiO₂.  Alamar blue proliferation assays using embryoid bodies derived from human embryonic stem cells confirmed the 3t3 fibroblast results: Again the non-hollow Ni-SiO₂ was the least toxic complex engineered nanomaterial, and hollow Ni-SiO₂ and Ni-on-SiO₂nanomaterial showed similar toxicities.

We are currently extending these studies to include a thorough physiochemical assessment of these nanomaterials, including agglomeration, settling and dissolution. Combined with the toxicity studies, this will allow us to draw connections between the physicochemical properties of the nanomaterials and possible toxicity pathways, and thus ultimately allow a first step towards structure-toxicity correlations. Our results thus serve to establish an experimental protocol for further studies into complex engineering nanomaterials.