TiO2 along with nano-TiO2 are commonly found in consumer products. In vivo studies have observed an accumulation of nano-TiO2 in macrophages. However, characteristics of nano-TiO2 determining toxicity remain unclear. In our study, the cytotoxic effects of 14 diverse nano-TiO2 on THP-1 macrophage-like cells were measured by 3 cytotoxicity assays (MTS, WST-1 and LDH). Total averaged cytotoxicity was calculated using principal component analysis. Characteristics of all 14 nano-TiO2 included hydrodynamic diameter, zeta potential, shape, polydispersity index (PDI) and concentration; moreover, crystal form, specific surface area and crystallite size were measured for 10 nano-TiO2.The variables affecting cytotoxicity were chosen using LASSO (least absolute shrinkage and selection operator). Except for concentration, PDI in media measured within 1 h after preparation of the nanomaterial dispersion was selected as a variable affecting cytotoxicity: stable dispersion resulted in higher cytotoxic effects. Crystallite size has been shown to have nonlinear effects (particles of sizes between 20 and 60 nm were cytotoxic while smaller and larger ones were not) and thus it has been excluded from LASSO. The shape (particles/fibre) and crystal form did not affect the cytotoxicity. PDI and the nonlinear effect of size could be an explanation for the inconsistencies of the cytotoxicity of nano-TiO2 in various studies.

Department of Computer Science Czech Technical University Prague Prague 121 35 Czech Republic

Department of Genetic Toxicology and Nanotoxicology Institute of Experimental Medicine of the Czech Academy of Sciences Prague 14220 Czech Republic

Department of Genetic Toxicology and Nanotoxicology Institute of Experimental Medicine of the Czech Academy of Sciences Prague 14220 Czech Republic; Genetic and Molecular Biology Graduate Program Federal University of Goias Goiás 74690 900 Brazil

Department of Genetic Toxicology and Nanotoxicology Institute of Experimental Medicine of the Czech Academy of Sciences Prague 14220 Czech Republic; Institute for Environmental Studies Faculty of Science Charles University Benatska 2 Prague 2 12801 Czech Republic

Department of Genetic Toxicology and Nanotoxicology Institute of Experimental Medicine of the Czech Academy of Sciences Prague 14220 Czech Republic; Laboratory for Risk Reesearch and Management Faculty of Safety Engineering VSB Technical University of Ostrava Ostrava 700 30 Czech Republic

Microscopy Center Electron Microscopy Core Facility Institute of Molecular Genetics ASCR v v i of the Czech Academy of Sciences Prague 142 20 Czech Republic

Microscopy Center Electron Microscopy Core Facility Institute of Molecular Genetics ASCR v v i of the Czech Academy of Sciences Prague 142 20 Czech Republic; Department of Biology of the Cell Nucleus Institute of Molecular Genetics ASCR v v i of the Czech Academy of Sciences Prague 142 20 Czech Republic

Precheza Prerov 751 52 Czech Republic

References provided by Crossref.org

Testing Strategies of the In Vitro Micronucleus Assay for the Genotoxicity Assessment of Nanomaterials in BEAS-2B Cells

Molecular Responses in THP-1 Macrophage-Like Cells Exposed to Diverse Nanoparticles