Céline Botta

Structural Degradation at the Surface of a TiO2-Based Nanomaterial Used in Cosmetics

A number of commercialized nanomaterials incorporate TiO(2) nanoparticles. Studying their structural stability in media mimicking the environment or the conditions of use is crucial in understanding their potential eco-toxicological effects. We focused here on a hydrophobic TiO(2) nanoparticle-based formulation used in cosmetics: T-Lite SF. It is composed of a TiO(2) core, coated with two successive protective layers of Al(OH)(3), and polydimethylsiloxane. Soon after contact with water (pH = 5, low ionic strength), the T-Lite SF becomes hydrophilic and form aggregates. During this aging, 90%wt of the total Si of the organic layer is desorbed, and the PDMS remaining at the surface is oxidized. The Al(OH)(3) layer is also affected but remains sorbed at the surface. This remaining Al-based layer still protects from the production of superoxide ions from the photoactive/phototoxic TiO(2) core in our experimental conditions.

TiO2-based nanoparticles released in water from commercialized sunscreens in a life-cycle perspective: Structures and quantities

This work investigates the physical-chemical evolution during artificial aging in water of four commercialized sunscreens containing TiO₂-based nanocomposites. Sunscreens were analyzed in terms of mineralogy and TiO₂ concentration. The residues formed after aging were characterized in size, shape, chemistry and surface properties. The results showed that a significant fraction of nano-TiO₂ residues was released from all sunscreens, despite their heterogeneous behaviors. A stable dispersion of submicronic aggregates of nanoparticles was generated, representing up to 38 w/w% of the amount of sunscreen, and containing up to 30% of the total nano-TiO₂ initially present in the creams. The stability of the dispersion was tested as a function of salt concentration, revealing that in seawater conditions, a major part of these nano-TiO₂ residues will aggregate and sediment. These results were put in perspective with consumption and life cycle of sunscreens to estimate the amount of nano-TiO₂ potentially released into AQUATIC environment.

Environmental impact of sunscreen nanomaterials: Ecotoxicity and genotoxicity of altered TiO2 nanocomposites on Vicia faba

Mineral sunscreen nanocomposites, based on a nano-TiO(2) core, coated with aluminium hydroxide and dimethicone films, were submitted to an artificial ageing process. The resulting Altered TiO(2) Nanocomposites (ATN) were then tested in the liquid phase on the plant model Vicia faba, which was exposed 48 h to three nominal concentrations: 5, 25 and 50 mg ATN/L. Plant growth, photosystem II maximum quantum yield, genotoxicity (micronucleus test) and phytochelatins levels showed no change compared to controls. Oxidative stress biomarkers remained unchanged in shoots while in roots, glutathione reductase activity decreased at 50 mg ATN/L and ascorbate peroxidase activity decreased for 5 and 25 mg ATN/L. Nevertheless, despite the weak response of biological endpoints, ICP-MS measurements revealed high Ti and Al concentrations in roots, and X-ray fluorescence micro-spectroscopy revealed titanium internalization in superficial root tissues. Eventual long-term effects on plants may occur.

Genotoxicity of visible light (400–800 nm) and photoprotection assessment of ectoin, l-ergothioneine and mannitol and four sunscreens

This study was designed to determine the genotoxic effects of visible (400-800nm) and ultraviolet A (UVA)/visible (315-800nm) lights on human keratinocytes and CHO cells. The alkaline comet assay was used to quantify DNA-damage. In addition, photo-dependent cytogenetic lesions were assessed in CHO cells by the micronucleus test. Three protective compounds [ectoin, l-ergothioneine (ERT) and mannitol] were tested with the comet assay for their effectiveness to reduce DNA single-strand breaks (SSB). Finally, the genomic photoprotections of two broad-band sunscreens and their tinted analogues were assessed by the comet assay. The WST-1 cytotoxicity assay revealed a decrease of the keratinocyte viability of 30% and 13% for the highest UVA/visible and visible irradiations (15 and 13.8J/cm(2), respectively). Visible as well as UVA/visible lights induced DNA SSB and micronuclei, in a dose-dependent manner. The level of DNA breakage induced by visible light was 50% of the one generated by UVA/visible irradiation. However, UVA radiations were 10 times more effective than visible radiations to produce SSB. The DNA lesions induced by visible and UVA/visible lights were reduced after a 1-h preincubation period with the three tested compounds. The maximal protective effects were 92.7%, 97.9% and 52.0% for ectoin (0.1mM), ERT (0.5mM) and mannitol (1.5mM), respectively, against visible light and 68.9%, 59.8% and 62.7% for ectoin (0.1mM), ERT (0.5mM) and mannitol (1.5mM), respectively, against UVA/visible light. Thus, visible light was genotoxic on human keratinocytes and CHO cells through oxidative stress mechanisms similar to the ones induced by UVA radiations. The four tested sunscreens efficiently prevented DNA lesions that were induced by both visible and UVA/visible irradiations. The tinted sunscreens were slightly more effective that their colorless analogues. There is a need to complement sunscreen formulations with additional molecules to obtain a complete internal and external photoprotection against both UVA and visible lights.

Lowering of 5-nitroimidazole's mutagenicity: Towards optimal antiparasitic pharmacophore

To improve the antiparasitic pharmacophore, 20 5-nitroimidazoles bearing an arylsulfonylmethyl group were prepared from commercial imidazoles. The antiparasitic activity of these molecules was assessed against Trichomonas vaginalis, the in vitro cytotoxicity was evaluated on human monocytes and the mutagenicity was determined by the Salmonella mutagenicity assay. All IC(50) on T. vaginalis were below the one of metronidazole. The determination of the specificity indexes (SIs), defined as the ratios of the cytotoxic activity and the antitrichomonas activity, indicated that 11 derivatives had a SI over the one of metronidazole. Molecules, bearing an additional methyl group on the 2-position, showed a lower mutagenicity than metronidazole. Moreover, three derivatives were characterized by a low mutagenicity and an efficient antitrichomonas activity.

Ecotoxicological assessment of TiO2 byproducts on the earthworm Eisenia fetida

The increasing production of nanomaterials will in turn increase the release of nanosized byproducts to the environment. The aim of this study was to evaluate the behaviour, uptake and ecotoxicity of TiO(2) byproducts in the earthworm Eisenia fetida. Worms were exposed to suspensions containing 0.1, 1 and 10 mg/L of byproducts for 24 h. Size of TiO(2) byproducts showed aggregation of particles up to 700 μm with laser diffraction. Only worms exposed at 10 mg/L showed bioaccumulation of titanium (ICP-AES), increasing expression of metallothionein and superoxide dismutase mRNA (Real-time PCR) and induction of apoptotic activity (Apostain and TUNEL). TiO(2) byproducts did not induce cytotoxicity on cœlomocytes, but a significant decrease of phagocytosis was observed starting from 0.1 mg/L. In conclusion, bioaccumulation of byproducts and their production of reactive oxygen species could be responsible for the alteration of the antioxidant system in worms.

Effects of UVA and visible light on the photogenotoxicity of benzo[a]pyrene and pyrene.

This study investigated the role of UVA/visible light (U, 320–800 nm) and visible light (V, 400–800 nm) in the phototoxicity and photogenotoxicity of two ubiquitous polycyclic aromatic hydrocarbons (PAH): benzo[a]pyrene (BaP) and Pyrene (Pyr). These mechanisms were evaluated by the WST‐1 test and the comet assay on normal human keratinocytes (NHK) and by the micronucleus test on CHO cells. The production of reactive oxygen species (ROS) was assessed through the induction of 8‐oxodeoxyguanine (8‐oxodG) lesions by immunofluorescence staining in NHK. Results of the WST‐1 test revealed the phototoxic properties of BaP and Pyr after irradiation with U and V lights. BaP presented the highest phototoxic properties. Results of the comet assay showed that U‐ and V‐irradiated BaP and Pyr induced increasing rates of DNA single‐strand breaks in NHK, in a dose dependent manner. The tested PAH could also induce increased levels of micronuclei in CHO cells after U and V irradiations. Increasing 8‐oxodG levels were detected after U and V irradiations in BaP‐ and Pyr‐treated keratinocytes and confirmed the involvement of ROS in the photogenotoxicity of PAH. Overall, this study highlighted the existence of an alternative pathway of PAH genotoxicity that is induced by UVA and/or visible light. Visible light is suggested to photoactivate PAH by a mechanism which is mainly based on oxidative reactions.

Bioenergetics and DNA alteration of normal human fibroblasts by hexavalent chromium.

The effects of hexavalent chromium on mitochondria of normal human fibroblasts were investigated through the measurement of oxygen consumption, and its genotoxic effect through the analysis of chromium DNA adducts and oxidative DNA lesions. ROS production was also quantified. Chromium diminished oxygen consumption by cells in a concentration-dependent manner (IC(50)=66±8μM). This effect can be attributed to an alteration in mitochondrial functions, leading to defective glucose catabolism. The Comet assay, performed with and without the lesion-specific enzyme formamidopyrimidine-DNA glycosylase (Fpg), highlighted the extent of oxidative DNA base damage. DNA base damage was induced with low concentrations (0.5-3μM) of Cr(VI), whereas bioenergetic disturbance was only observed at higher concentrations (20-500μM).

Environmental fate of nanoparticles: physical chemical and biological aspects - a few snapshots

The environmental risk that nanomaterials can undergo is a major problem, which could prevent the commercial development of nanoproducts, especially in technology domains corresponding to large distribution: cosmetics, composite materials, civil engineering materials and leisure materials. The risk assessment is based on a complex approach, which implies the knowledge of the degradation mechanisms of the nanoproducts in aquatic media (kinetics and chemical change), the quantities that are distributed in the different ecosystem compartments and the biological effects on various targets (bacterial micro-organisms, primary and secondary predators). The paper aims at showing the unique surface properties of nanomaterials and especially when the size is decreasing largely less than 100 nm, the stability and the eventual degradation of intermediate nanomaterials, e.g., some composites used in sunscreens. The biological effects of the nanomaterials depends on their unique properties and especially the large surface tension as the size decreases, the defects within the bulk and on the surface at the origin of the production of ROS. The molecular mechanisms underlying the toxicity are described especially in terms of oxidation-reduction reactions owing to surface reactivity, surface atoms dissolution, oxidative dissolution and dissolution.