Caratterizzazione di nano e micropolveri di biossido di titanio in fluidi simulanti il tratto gastro-intestinale

Titanium dioxide (TiO2) is one of the most popular pigments in use today. TiO2 is authorised as a food additive in the European Union (E171) for colouring. Human ingestion and accumulation of TiO2 particles has dramatically increased since the application of TiO2 NPs in food-industry raised. Food grade TiO2 is a micrometric powder. However, it contains a variable fraction of nano-sized particles; their size in nanoscale range is linked to potential adverse effects on human health. Validated analytical methods to assess size distribution in food matrices are not currently available. Size distribution of nanomaterials is highly dependent upon the matrix in which are found, due to the high tendency to form agglomerates or aggregates. The first part of the present study aims to develop an analytical method for the dimensional characterization of TiO2 particles in food matrices. The method was developed using the asymmetric flow field-flow fractionation (AF4) analytical approach combined with ultra violet (UV), multi angle light scattering (MALS), inductively coupled plasma mass spectrometry (ICP-MS) and dynamic light scattering (DLS) detectors. The method was successfully developed for nanometric powders, while for food-grade powders the instability of suspension and the interaction membrane-particle, have been identified as key factors for a further optimization of the method. In the second part of the study DLS technique was used to investigate the size distribution of TiO2 powders once ingested. Agglomeration of nanomaterials upon ingestion was demonstrated in several studies. However, there is a poor knowledge on the physico-chemical parameters driving this process. Here, an in vitro model of the gastro-intestinal (GI) tract was used to simulate the human digestion process by applying physiologically based conditions, i.e. chemical composition of digestive fluids, pH and residence time periods typical for each compartment (mouth, stomach and intestine). The results demonstrate that agglomeration of TiO2 particles occurs in the stomach and in the intestine but not in saliva. In the stomach, agglomeration seems a consequence of the low pH, while the strong ionic strength (IS) and the adsorption of phosphate ions play and important role in duodenal fluid. These results may have important implications both for developing safe NMs and in performing nanotoxicological studies, because NPs size affect translocation into cells and interaction with human body. This project was partially conducted the Biomedical and Inorganic Chemistry Department of LNE (National Laboratory for Metrology and Testing) in Paris and financially supported by Erasmus+ Programme.