EFSA Project on the use of New Approach Methodologies (NAMs) for the hazard assessment of nanofibres. Lot 1, nanocellulose oral exposure: gastrointestinal digestion, nanofibres uptake and local effects

Nanocellulose (NC) is an emerging material in the food sector with several prospective application areas. Three main types of NC exist, i.e. bacterial NC (BNC), nanofibrillated cellulose (NFC), and cellulose nanocrystals (CNC). The biological sources and processing conditions affect several physicochemical parameters of NC. In the present project, a NAM-based IATA for addressing data gaps in the assessment of potential hazards associated to NC oral exposure was considered. This IATA focused on three main pillars, i.e. (i) assessment of the uptake and potential crossing of the intestinal barrier by NC, (ii) assessment of local effects, including inflammation and genotoxicity, on the gastrointestinal epithelia, and (iii) assessment of any digestion or degradation of NC by the human microbiome. Eight NC samples belonging to the three NC types, plus a comparator in the micro-range, were selected as study materials and submitted to a thorough physicochemical characterisation. A battery of in vitro tests was used to provide insight into NC hazard and mode of action according to a tiered approach, which lead to selection of three materials belonging to the three main NC types for in depth-testing. Cell uptake of these materials was demonstrated, and such uptake was greater in a triculture model, which better simulates the barrier properties of the human intestinal epithelium, as compared to Caco-2 monolayers. Uptake was the greatest in repeated exposure conditions, in which intestinal barrier crossing was demonstrated for CNC. Pro-inflammatory responses accompanied by massive NC uptake in macrophages, indicative for potential immunotoxicological effects, and barrier function impairment were observed, whereas no indications for genotoxicity were obtained. Finally, no formation of smaller particles following colonic fermentation of NC was observed. For the integration of these results in regulatory hazard assessment of NC after oral exposure, prospective use of NC as novel food or as food additive was considered.