Mechanisms of (photo)toxicity of TiO2 nanomaterials (NM103, NM104, NM105): using high-throughput gene expression in Enchytraeus crypticus

Abstract

Titanium dioxide (TiO₂) based nanomaterials (NMs) are among the most produced NMs worldwide. When irradiated with light, particularly UV, TiO₂ is photoactive, a property that is explored for several purposes. There are an increasing number of reports on the negative effects of photoactivated TiO₂ on non-target organisms. We have here studied the effect of a suite of reference type TiO₂ NMs (i.e. NM103, NM104, and NM105 and compared these to the bulk) with and without UV radiation to the oligochaete Enchytraeus crypticus. High-throughput gene expression was used to assess the molecular mechanisms, while also anchoring it to the known effects at the organism level (i.e., reproduction). Results showed that the photoactivity of TiO₂ (UV exposed) played a major role in enhancing TiO₂ toxicity, activating the transcription of oxidative stress, lysosome damage and apoptosis mechanisms. For non-UV activated TiO₂, where toxicity at the organism level (reproduction) was lower, results showed potential for long-term effects (i.e., mutagenic and epigenetic). NM specific mechanisms were identified: NM103 affected transcription and translation, NM104_UV negatively affected the reproductive system/organs, and NM105_UV activated superoxide anion response. Results provided mechanistic information on UV-related phototoxicity of TiO₂ materials and evidence for the potential long-term effects.