A safer formulation concept for flame-generated engineered nanomaterials

S. Gass, G. Pyrgiotakis, J.M. Cohen, G.A. Sotiriou, S.E. Pratsinis, P. Demokritou
Harvard School of Public Health, US

Keywords: ENM, nanotoxicology, FSP, core-shell nanoparticles, SiO2 coating, mitigating toxicity

Summary:

Engineering less toxic ENMs that maintain valuable functional properties is crucial to the sustainability of the nanotech industry. Core-shell nanoparticles are particularly interesting in this regard. They exhibit the surface properties of their shells while preserving certain bulk properties of their core material. Careful selection of a biologically “inert” nanothin SiO2-shell can therefore shield otherwise toxic core materials from their surroundings. Here, four industry-relevant ENMs (CeO2, Fe2O3, Ag, ZnO) were synthesized and coated using a modified FSP-based Versatile Engineered Nanomaterial Generation System (VENGES). The SiO2 surface coating of the ENMs takes place in-situ, in a one step, dry process. Particles were characterized with respect to primary particle size, crystallinity, morphology, and electrophoretic mobility by X-Ray Diffraction, Brunauer-Emmett-Teller powder specific surface area measurements, Transmission Electron Microscopy, and Dynamic Light Scattering. The SiO2 coating efficiency of the process was evaluated by X-Ray Photoelectron Spectroscopy and Isopropanol Chemisorption. The relative toxicity of coated vs. uncoated ENMs was evaluated using a number of cellular assays (MTT, LDH, Live/Dead) and multiple cell lines (A549 cancer alveolar epithelial cells and macrophages). We demonstrate significant differences in induced toxicity between coated and uncoated particles.