| Summary: | Cellulose nanomaterials (CNMs) emerged as an important group of nanomaterials with potential applications in multiple food-related products, as zero-calorie filler/thickener/stabilizer, or as a substitute for petroleum-based food packaging materials. Human oral exposure to CNMs is increasing, but little is known about the potential adverse biological impact of CNMs on human gastrointestinal tract. To contribute to the development of innovative CNMs for the food sector and to their early-stage safety assessment, in this work new CNMs were prepared, and their cytotoxic effects were investigated in human intestinal cell lines. Two cellulose micro/nanofibrillated (CNFs), were synthetized from industrial bleached Eucalyptus globulus kraft pulp using different pretreatments (enzymatic and TEMPO-mediated oxidation) followed by a high-pressure homogenization process. Potential cytotoxic effects were evaluated by the MTT assay using two human intestinal cell models (Caco-2 and HT29-MTX-E12). Since in humans the digestion process may modify the physicochemical properties of NMs, potentially influencing biological outcomes, the CNFs were subjected to a harmonized in vitro digestion method before cytotoxicity testing. No cytotoxic effect was observed after 24h exposure to the undigested CNFs in the concentration-range tested (3.1 µg/mL-200 µg/mL), irrespectively of the cell line used. Similar results were obtained for the digested CNFs for concentrations up to 14.3 µg/mL. The observation that the in vitro digestion mixture was cytotoxic by itself for concentrations above 7.6 % (v/v) (i.e., equivalent to CNMs exposure > 14.3 µg/mL) impaired cytotoxicity assessment at higher CNFs concentrations. Complementary cytotoxicity assays and future optimization of the in vitro digestion procedure to reduce its toxicity are underway, to refine the assessment of CNFs cytotoxicity, particularly after digestion. Furthermore, genotoxicity studies will increase the knowledge on the cellular effects of CNMs in the human intestine, contributing to the safety assessment of CNMs early in its development stage, towards sustainable innovation of nanomaterials, thereby protecting human health.
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