1 Supporting Information Oxidative stress induced by pure and iron-doped amorphous silica nanoparticles in sub- toxic conditions Running title: Oxidative stress and cytotoxicity of amorphous nanosilica Dorota Napierska † , Virginie Rabolli ‡ , Leen C.J. Thomassen § , David Dinsdale ║ , Catherine Princen ‡ , Laetitia Gonzalez ¶ , Katrien L.C. Poels ⊥ , Micheline Kirsch-Volders ¶ , Dominique Lison ‡ , Johan A. Martens § and Peter H. Hoet † * † Unit for Lung Toxicology, Katholieke Universiteit Leuven, Herestraat 49, O&N1-706, 3000 Leuven, Belgium ‡ Industrial Toxicology and Occupational Medicine unit, Universite´ Catholique de Louvain, 1200 Brussels, Belgium § Center for Surface Chemistry and Catalysis, Katholieke Universiteit Leuven, 3001 Heverlee, Belgium ║ MRC Toxicology Unit, Lancaster Road, Leicester LE1 9HN, UK ¶ Laboratory of Cell Genetics, Vrije Universiteit Brussel, 1050 Brussels, Belgium ⊥ Laboratory for Occupational Hygiene and Toxicology, Katholieke Universiteit Leuven, 3000 Leuven, Belgium *To whom correspondence should be addressed. Unit for Lung Toxicology, Katholieke Universiteit Leuven, Herestraat 49, O&N1-706, 3000 Leuven, Belgium. Tel. +32 16330197, Fax: +32 16 330806 E-mail: peter.hoet@med.kuleuven.be