Impatto delle nano-formulazioni nutraceutiche a base lipidica sulla barriera gastrointestinale: valutazioni in vitro e in vivo.

Nanomaterials (NMs) offer great promise in a wide range of disciplines such as chemistry, physics, biology, medicine, and engineering because of their unique properties, different from those of their bulk counterparts. While NMs are becoming commercially available, our exposure to NMs is increasing over the years, yet there is little understanding of their toxicological properties and long-term impact on human health. Therefore, there is the need to generate standardized toxicological analyses based on in vitro experiments to predict the hazard of NMs. In this thesis, as a part of the European project BIORIMA, we propose the evaluation of the impact on the gastrointestinal (GI) barrier of a nutraceutical formulation made up from lipid- based nanoparticles (LNPs) charged or not with melatonin (MLT), using a combination of in vitro and in vivo analyses, in order to assess NM effects in complex and physiologically relevant biological systems. Since these NMs can reach the GI tract through voluntary exposure, they were subjected to an in vitro simulated human digestion system (SHDS) to reproduce the digestive process occurring in humans. Cell viability, barrier permeability and inflammation of the NMs were studied on a Caco-2 intestinal barrier model. None of the parameters studied showed significant alterations, with the except of the pro/anti-inflammatory cytokines and TEER after SHDS which were significantly perturbated. LNPs impact was contextually tested in CD1 mice exposed to two different concentrations of LNPs. Gene expression analysis of tight junction proteins and inflammatory molecules of each tract of small intestine’s samples was carried out. We found the major effects of LNPs in jejunum, with a significant up-regulation of claudin 5 gene for highest dose of LNPs loaded with MLT, and changes in both pro- and anti-inflammatory cytokines. The data were then compared with those obtained from in vitro analysis; it was confirmed that the digestion process affects the impact of NMs differently in both Caco-2 and murine models. In conclusion, we suggest that a combination of in vitro cellular models simulating the physiological digestion process with in vivo tests may represent a complementary screening strategy for the assessment of the biocompatibility of ingested NMs.