Bio accessibility of tire-associated organic chemicals in fish gut (Oncorhynchus mykiss): insights from an in vitro digestion model

Tire and Road Wear Particles (TRWP) account for an important part of the anthropogenic particles released into the environment. There are scientific knowledge gaps as to the potential bio accessibility of chemicals associated with TRWP to aquatic organisms. This study aimed to investigate the solubilization of five tire-associated chemicals into fish gut using an in vitro digestion model (Oncorhynchus mykiss). Our results show that the targeted compounds were partly and rapidly solubilized into simulated fluids (SF) present in the gastrointestinal tract within a typical gut transit time for fish (3h in SFGASTRIC and 24h in SFINTESTINAL). The effects of food co-ingestion on the solubilization of tire-associated chemicals was compound-specific and either lowered or stimulated their solubilization into the gut fluids. Therefore, the uptake of the tire associated chemicals by the epithelial cells and related toxicity to fish need to be investigated

Titanium dioxide particles in food : characterization, fate in digestive fluids and impact on human gut microbiota

Le dioxyde de titane (TiO2) est un oxyde métallique utilisé en tant que pigment blanc, par exemple dans les enrobages de confiseries. Sachant que la forme alimentaire (E171/IN171) contient des nanoparticules (NPs), et que ces dernières sont classifiées comme potentiellement dangereuses par inhalation, nos travaux ont eu pour but de déterminer le devenir et l’impact des particules de E171 après ingestion. Plusieurs lots de poudre E171 ont été caractérisés et comparés à un lot de poudre P25, variété de référence de TiO2 en toxicologie (100% NPs). Nos résultats ont confirmé que la forme E171 contient des NPs, cependant à en quantité inférieure au seuil définissant l’étiquetage des nanomatériaux (50%). Comme les mêmes particules de E171 sont retrouvées intactes dans les extraits d’enrobage de plusieurs confiseries et que les propriétés physicochimiques des deux formes E171 et P25 sont très différentes, la forme E171 pourrait ainsi être préférée à l’actuel modèle P25 pour les études portant sur l’impact du TiO2 par ingestion. Le suivi des particules des variétés E171 et P25 au cours d’une digestion in vitro a montré leur forte agglomération, due à l’adsorption d’ions et de protéines composant les fluides digestifs. Cette forte agglomération (jusqu’à 90 μm dans l’intestin) explique le faible taux d’absorption du TiO2 observé in vivo. Au contact d’une flore intestinale humaine reconstituée, aucune des formes E171 ou P25 n’a eu d’effet sur la viabilité et la richesse écologique du microbiote après exposition à une dose singulière de TiO2 équivalente à l’ingestion d’une confiserie. Ces résultats doivent être à l’avenir confirmés dans le cadre d’une consommation régulière.Titanium dioxide (TiO2) is a white metal oxide commonly used as a coloring agent in food products, constituting for example the coating of confectionary. Considering that food-grade TiO2 (E171/INS171) contains nanoparticles (NPs) and that TiO2 NPs are classified as potentially harmful for humans by inhalation, we aimed to determine the fate and impact of TiO2 particles via ingestion. The physicochemical characterization of E171 samples confirmed that E171 contains NPs, however below the threshold defining the labelling of nanomaterial (50%). Moreover, they resemble TiO2 extracted from the coating of several confectioneries, indicating that they can be used directly as models of ingested particles. Furthermore, the physicochemical properties of E171 were proved to be very different from those of P25, a kind of TiO2 used as a reference in toxicology (100% NPs). Food grade E171 TiO2 may be thus preferred to the currently used model P25 for further studies on the impact of TiO2 via ingestion. Monitoring food grade TiO2 at each step of an in vitro digestion showed that, due to interactions with both ions and proteins composing the digestive fluids, TiO2 particles agglomerated all along the digestion and formed large agglomerates (up to 90μm in the intestinal phase), explaining the low absorption rate of TiO2 after ingestion observed in vivo. Finally, the impact of TiO2 on the human gut microbiota was assessed. No impact on the human gut microbiota viability and ecological richness was observed after a single dose of TiO2 equivalent to the ingestion of one piece of candy. These results are still to be confirmed for a chronic ingestion

Following titanium dioxide from a food product to the intestine: what’s new?

Following titanium dioxide from a food product to the intestine: what’s new?. 7th International IMBG meeting on Metallic Nanoparticles: Health, Environment, applications and Safer-by-Desig

Physical evolution of titanium dioxide particles in digestive fluids

Eating titanium dioxide, an approved food color additive (E171), has raised some concerns, mainly due to its content in nanoparticles (NPs). To understand how it is handled in the gastro-intestinal tract, we analyzed the behavior of food grade TiO2 (~20% NPs, 120 nm) and P25 TiO2 NPs (~100% NPs, 25 nm) in digestive fluids through a standardized static in vitro digestion protocol. After each step of digestion (i.e. saliva, gastric and intestinal step), the size of the particles and the surface charge changes were characterized using laser particle size distribution analysis and zeta potential measurements and compared to the values obtained for control digestion (without the digestion enzymes). Both food grade and P25 particles strongly agglomerate in digestive fluids due to the presence of salts and proteins. The largest agglomerates were formed in the intestinal fluid, with diameters up to several ten hundreds of micrometers. The nature of adsorbed proteins was determined by denaturing gradient gel electrophoresis (DGGE) after separation from particles. All TiO2 samples interacted with alpha-amylase and only one sample with pepsin. Finally, E171 (~20% NPs) and P25 TiO2 (100% NPs) do not appear to exist as nanometric entities all along the steps of the in vitro digestion protocol, which constitutes good news considering the concerns about the effects of ingested nano-products. However, these large agglomerates may be transformed in contact with the epithelium; moreover the adsorption of enzymes may have a major impact on the digestion process. Both issues are currently under investigation

Is p25 a realistic model to study the toxicity of tio2 in the gastro-intestinal tract?

National audienc

In-vitro digestion of Tire and Road Wear Particles: Bioavailability of metals and Polycyclic Aromatic Hydrocarbons

The potential impact of Tire and Road Wear Particles (TRWP) on aquatic organisms has recently gained attention since the occurrence of TRWP in the aquatic environment has been observed in surface water and sediments of numerous regions. Moreover, the ingestion of TRWP by aquatic species, including fish, has recently been demonstrated. However, data regarding the bioavailability and toxicity of contaminants associated with these particles are still lacking. This study aimed (i) to characterize the solubilization potential of metals and PAHs from tire particles and TRWP in Simulated Gastric Fluids (SFG) and Simulated Intestinal Fluids (SIF) designed to mimic Oncorhynchus mykiss (Rainbow Trout) gut conditions and (ii) to assess the impact of influencing factors such as co-ingestion of natural food organic matter on the compounds solubilization. Our results showed that solubilization of all metals and PAHs were enhanced by up to 10-fold in simulated gut fluids compared to solubilization in the control (phosphate buffer saline solution). Zn was highly solubilized after an in-vitro digestion of 24-h with a final concentration in SIF of 3,2 µg.L-1 corresponding to 23 % of the total Zn concentration in TRWP. Five PAHs (Fluoranthene, Phenanthrene, Pyrene, Benzo (e) Pyrene and Benzo (g,h,i) perylene) were quantified in SIF after an incubation time of 24-h and the concentration of individual PAHs in SIF ranged from 42 to 3092 ng.L-1 which represented 0,4 – 1,5 % of their total concentration measured in tire particles. Metals were highly solubilized by the acidic SGF (pH = 2) but only a weak solubilization was observed in neutral SIF (pH = 7,4). Contrastingly, PAHs were not solubilized in SGF and highly solubilized in SIF which was proved to contain high quantities of proteins and surfactants forming micelles. This emphasise the importance of pH in the solubilization of metals and of bile surfactants and organic matter in the solubilization of PAHs from TRWP and brings new insights on the bioavailability of metals and organic pollutants from TRWP. Overall, our results demonstrate the importance of accounting for the ingestion of TRWP as an important route of exposure to metals and PAHs for aquatic organisms. As the solubilization of potential toxic compounds was greatly enhanced by the gut fluids and leads to bioavailability of these compounds, further studies investigating the uptake by the epithelial cells and transfer throughout the whole organism will be performed

Impact of food grade and nano-TiO2 on human gut microbiota

International audienc

Impact of food grade and nano-TiO2 on human gut microbiota

International audienc