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Inorganic food additives: characterization and fate during digestion

H. Terrisse, S. Quillard, B. Humbert

Our objective is to characterize different food additives, such as titanium dioxide (E171), colloidal silver and calcium phosphates (E341), which are currently present as nanoparticles in different food formulations (confectionery, infant milk), or pharmaceuticals. We first determine the physico-chemical characteristics of these compounds using a wide range of techniques (electron microscopy, infrared spectroscopy, Raman, solid state NMR, XPS, X-ray diffraction, UV-visible, etc.). We then analyze their properties at the interfaces with biological media, and identify their interactions with molecules present in the digestive system (proteins, enzymes) or in cell walls (phospholipids), using adsorption isotherms, zeta potential measurements, and spectroscopic tools to probe the surface of the particles.

To go further : [TiO2-Phospholipids], [E171 Caracterisation]

Other people involved : 
Y. El Moussaoui (2020-2023).
 Keywords : 
TiO2, colloidal silver, calcium phosphates.

  • TiO2 project

Interactions between titanium dioxide and some phospholipid molecules have been highlighted [1, 2] and led us to finely characterize the modes of binding of small phosphate molecules to the surface of TiO2, both through experimental methods (adsorption isotherms, infrared and NMR spectroscopies, zeta potential measurements), and through theoretical approaches, in collaboration with the IMN MIOPS team (Camille LATOUCHE).

In addition, the food additive E171 (composed of anatase, and present in many food formulations, mainly for children) has been characterized by a wide range of techniques and compared to a compound, P25 (mixture of anatase and rutile), widely studied in the literature, particularly in terms of toxicology. This study showed that their surface properties are in fact very different and that P25 is not a suitable model for identifying the toxicity of food grade titanium dioxide [3]. The E171 additive was also characterized after extraction of different chewing-gum coatings [4], and its fate in the gastrointestinal tract was elucidated using an in vitro digester [5], in collaboration with INRAE (Marie-Hélène ROPERS, BIA Unit, Nantes). This study showed that interactions exist between TiO2 particles and certain enzymes present in the digestive environment.

[1] Quoc Chon LE thesis, Nantes University, 2014

[2] Q.-C. LE et al., Colloids and Surface B : Biointerfaces, 123, 150-157 (2014)

[3] W. DUDEFOI, et al., Food Additives and Contaminants, Part A, 34(5), 653-665 (2017)

[4] W. DUDEFOI et al., Food Additives and Contaminants, Part A, 35(2), 211-221 (2018)

[5] William DUDEFOI thesis, Nantes University, 2017

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  •  Colloidal silver project

The physico-chemical characterization, using a wide range of analytical tools (electron microscopy, zeta potential, dynamic light scattering, elemental analysis by ICP-AES, Raman and UV-visible spectroscopy, X-ray absorption), of a large number of colloidal silver batches is under investigation, in collaboration with INRAE (Marie-Hélène ROPERS, BIA Unit, Nantes and Muriel MERCIER-BONIN, Toxalim Unit, Toulouse). In this context, studies on the exposure of model intestinal cells to colloidal silver solutions have been carried out [6], as well as animal experiments on mice, in order to identify tissues where silver bioaccumulation could occur.

[6] K. GILLOIS et al., Science of the Total Environment, 754, 142324 (2021)

Project: NANOSTRESS (supported by INRAE - BIA and Toxalim Units, 2018-2020)

Oral exposure to silver from food additives and supplements: physico-chemical transformations and consequences on the mucus in its dialogue with the intestinal microbiota in conditions of chronic stress.


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  • Calcium phosphate project

We are currently working on the fate of the food additive E341 (made up of calcium phosphates), present in infant milk in the form of fine nanometric needles, during digestion. The physico-chemical transformations undergone by this compound in the gastrointestinal tract are analyzed by ad hoc techniques (electron microscopy, solid state NMR, X-ray diffraction, IR-Raman spectroscopy, zeta potential), after setting up an in vitro digestion protocol, in collaboration with INRAE (Marie-Hélène ROPERS, BIA Unit, Nantes). The dissolution-recrystallization and adsorption processes of ionic or molecular species on the surface of the particles are highlighted, in order to identify the potential interactions of these nano-needles with certain proteins or digestive enzymes.

additifs nps3

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