In Vitro Biological Impact of Nanocellulose Fibers on Human Gut Bacteria and Gastrointestinal Cells

Abstract

Wood-derived nanofibrillated cellulose (NFC) has long been recognized as a valuable nanomaterial for food-related applications. However, the safety of NFC cannot be predicted just from the chemical nature of cellulose, and there is a need to establish the effect of the nanofibers on the gastrointestinal tract, to reassure the safe use of NFC in food-related products. The present work selected the intestinal cells Caco-2 and the gut bacteria Escherichia coli and Lactobacillus reuteri to evaluate the in vitro biological response to NFC. NFC materials with different surface modifications (carboxymethylation, hydroxypropyltrimethylammonium substitution, phosphorylation and sulfoethylation) and unmodified NFC were investigated. The materials were characterized in terms of surface functional group content, fiber morphology, zeta potential and degree of crystallinity. The Caco-2 cell response to the materials was evaluated by assessing metabolic activity and cell membrane integrity. The effects of the NFC materials on the model bacteria were evaluated by measuring bacterial growth (optical density at 600 nm) and by determining colony forming units counts after NFC exposure. Results showed no sign of cytotoxicity in Caco-2 cells exposed to the NFC materials, and NFC surface functionalization did not impact the cell response. Interestingly, a bacteriostatic effect on E. coli was observed while the materials did not affect the growth of L. reuteri. The present findings are foreseen to contribute to increase the knowledge about the potential oral toxicity of NFC and, in turn, add to the development of safe NFC-based food products.

In Vitro Investigation of Thiol-Functionalized Cellulose Nanofibrils as a Chronic Wound Environment Modulator

“…Overall, cys-CNF did not induce toxic effects on hDF when tested at a concentration up to 0.5 mg/mL, nor did the starting material c-CNF. These results confirm the safety profile of nanocellulose fibers when in contact with biological systems, as previously investigated with different functionalized CNF materials and diverse cell models [ 44 , 45 , 46 , 47 ]. Future studies should investigate the in vitro wound healing capacity of cys-CNF in terms of dermal and epidermal cell response (proliferation, migration, and differentiation).…”

Role of Surface Chemistry in the In Vitro Lung Response to Nanofibrillated Cellulose

“…It is well-recognized that the physicochemical features of nanomaterials may affect their toxicity [ 16 , 22 , 23 ], surface chemistry being one of the most relevant ones [ 18 ]. Surface modifications can impart new beneficial properties to nanocelluloses, increasing their applicability in, e.g., healthcare products and food packaging [ 24 ]. However, different functionalization will determine differences in the agglomeration rate, hydrophobicity, surface charge, and surface chemistry of nanocelluloses, which may affect their cellular uptake, interaction with subcellular organelles, and downstream biological responses [ 19 ].…”

“…However, different functionalization will determine differences in the agglomeration rate, hydrophobicity, surface charge, and surface chemistry of nanocelluloses, which may affect their cellular uptake, interaction with subcellular organelles, and downstream biological responses [ 19 ]. Surface chemistry was reported to drive in vitro inflammatory response to NFC [ 25 ], while no differences in cell metabolic activity or cell membrane integrity were observed when diverse in vitro cell models where exposed to differently functionalized NFC materials [ 14 , 24 , 25 ].…”

Nanocellulose Bio-Based Composites for Food Packaging

“…The effect of NC in the gastrointestinal tract was addressed in very few studies. A recent study evaluated the in vitro biological effect of unmodified and modified NC (carboxymethylation, phosphorylation, sulfoethylation and substitution with hydroxypropyltrimethylammonium) on human gut bacteria and gastrointestinal cells [ 142 ]. The metabolic activity and cell membrane integrity of intestinal cells Caco-2 and the growth of representative of microbiota bacteria were measured.…”

“…Results indicated no cytotoxicity after exposure to unmodified NFC and to surface functionalized NFC. Furthermore, a bacteriostatic effect on E. coli was observed but not on L. reuteri [ 142 ].…”