Bacterial Cellulose <i>In Vitro</i> Uptake\nby Macrophages, Epithelial Cells, and a Triculture Model of the Gastrointestinal\nTract

Bacterial cellulose (BC) has a long-standing human consumption\nhistory in different geographies without any report of adverse effects.\nDespite its unique textural and functional properties, the use of\nBC in food products in Europe is still restricted due to concerns\nover its nanosize. Here, we evaluated the potential uptake of celluloses\n(from plant and microbial sources, processed using different blenders)\nby macrophages (differentiated THP-1 cells) and human intestinal epithelial\ncells (Caco-2 and HT29-MTX cells) without (coculture) or with (triculture)\nRaji-B cells. A carbohydrate-binding module coupled to a green fluorescent\nprotein was employed to observe cellulose in the cell cultures by\nconfocal laser scanning microscopy and stimulated emission depletion\nmicroscopy. The methodology demonstrated excellent sensitivity, allowing\ndetection of single nanocrystals within cells. All celluloses were\ntaken up by the macrophages, without significantly compromising the\ncell’s metabolic viability. The viability of the cocultures\nwas also not affected. Furthermore, no internalization was observed\nin the triculture cell model that was exposed 24 h to BC and Avicel\nLM310. When (rarely) detected, cellulose particles were found on\nthe apical side of the membrane. Overall, the obtained results suggest\nthat BC should not be absorbed into the human gut.