Genotoxicity testing of different surface-functionalized SiO₂, ZrO₂ and silver nanomaterials in 3D human bronchial...

Inhalation is considered a critical uptake route for NMs, demanding for sound toxicity testing using relevant test systems. This study investigates cytotoxicity and genotoxicity in EpiAirway™ 3D human bronchial models using 16 well-characterized NMs, including surface-functionalized 15 nm SiO₂ (4 variants), 10 nm ZrO₂ (4), and nanosilver (3), ZnO NM-110, TiO₂ NM-105, BaSO₄ NM-220, and two AlOOH NMs. Cytotoxicity was assessed by LDH and ATP assays and genotoxicity by the alkaline comet assay. For 9 NMs, uptake was investigated using inductively coupled plasma-mass spectrometry (ICP-MS). Most NMs were neither cytotoxic nor genotoxic in vitro. ZnO displayed a dose-dependent genotoxicity between 10 and 25 µg/cm². Ag.50.citrate was genotoxic at 50 µg/cm². A marginal but still significant genotoxic response was observed for SiO₂.unmodified, SiO₂.phosphate and ZrO₂.TODS at 50 µg/cm². For all NMs for which uptake in the 3D models could be assessed, the amount taken up was below 5% of the applied mass doses and was furthermore dose dependent. For in vivo comparison, published in vivo genotoxicity data were used and in addition, at the beginning of this study, two NMs were randomly selected for short-term (5-day) rat inhalation studies with subsequent comet and micronucleus assays in lung and bone marrow cells, respectively, i.e., ZrO₂.acrylate and SiO₂.amino. Both substances were not genotoxic neither in vivo nor in vitro. EpiAirway™ 3D models appear useful for NM in vitro testing. Using 16 different NMs, this study confirms that genotoxicity is mainly determined by chemical composition of the core material.