RESUMO
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 1â¯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 60â¯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.