Assessment of the Influence of Crystalline Form on Cyto-Genotoxic and Inflammatory Effects Induced by TiO2 Nanoparticles on Human Bronchial and Alveolar Cells

Abstract

Titanium dioxide nanoparticles (TiO2NPs) are increasingly used in consumer products, industrial and medical applications, raising concerns on their potential toxicity. The available in vitro and in vivo studies on these NPs show controversial results. Crystalline structure is the physicochemical characteristic that seems to influence mainly TiO2NPs toxicity, so its effect needs to be further studied. We aimed to study whether and how crystalline form influences potential cyto-genotoxic and inflammatory effects induced by two commercial TiO2NPs (TiO2-A, mainly anatase; TiO2-B, mainly rutile) in human alveolar A549 and bronchial BEAS-2B cells exposed to 1–40 µg/mL. Cell viability (WST-1), membrane damage (LDH release), IL-6, IL-8 and TNF-α release (ELISA) and direct/oxidative DNA damage (fpg-comet assay) were evaluated. Physicochemical characterization included analysis of crystalline form (TEM and XRD), specific surface area (BET), agglomeration (DLS) and Z-potential (ELS). Our results show that TiO2-A NPs induce in BEAS-2B cytotoxicity and a slight inflammation and in A549 slight oxidative effects, whereas TiO2-B NPs induce genotoxic/oxidative effects in both cell lines, revealing different toxicity mechanisms for the two tested NPs. In conclusion, our study confirms the influence of crystalline form on cellular response, also demonstrating the suitability of our in vitro model to screen early TiO2NPs effects.

Influence of Titanium Dioxide Nanoparticles on Human Health and the Environment

“…Research has provided contradictory results regarding TiO 2 NPs’ genotoxicity [ 7 , 80 ]. Several studies found TiO 2 NPs to have no genotoxic effect [ 7 , 57 , 80 , 81 ].…”

“…Research has provided contradictory results regarding TiO 2 NPs’ genotoxicity [ 7 , 80 ]. Several studies found TiO 2 NPs to have no genotoxic effect [ 7 , 57 , 80 , 81 ]. Brandão et al examined TiO 2 NP-induced genotoxicity in human lung, liver, glial, and neuron cells [ 82 ].…”

“…At this point it should be noted that the cytotoxicity of TiO 2 NPs increased in the following order: amorphous > anatase > anatase/rutile; thus, amorphous TiO 2 NPs possessed greater toxic effect than anatase/rutile TiO 2 NPs [ 95 ]. Fresegna et al studied the cellular responses of human alveolar A549 and bronchial BEAS-2B cells to measure the cytotoxic and inflammatory effects of TiO 2 NPs in anatase and rutile forms [ 7 ]. They found that anatase TiO 2 NPs exerted greater cytotoxicity on bronchial cells compared to rutile TiO 2 NPs.…”

“…It has three crystalline structures: anatase, rutile, and brookite. Anatase is the most common type and rutile is the most stable form, while brookite is the rarest [ 7 ]. There is also amorphous TiO 2 , which is a non-crystalline form.…”

“…Despite this, more research is needed to address the bioaccumulation profile of TiO 2 and its associated biomagnification in the food web. To date, controversial results have been found when studying the toxicity of TiO 2 NPs, which may be due to different particle sizes, doses, culture media, or test methods used [ 7 , 16 ]. Recently, green nanotechnology has been adopted by researchers to ensure the biocompatible and environmentally friendly use of TiO 2 NPs by overcoming their drawbacks.…”