Assessment of the gastrointestinal fate of bacterial nanocellulose and its toxicological effects after repeated-dose oral administration

Bacterial nanocellulose (BNC), a nanofibrillar polysaccharide produced by certain acetic acid bacteria, may be used in food, pharma and many other applications. As with other nanoscale celluloses, the oral toxicology of BNC is still controversial. Therefore, we aimed to assess whether BNC is absorbed at the intestine following administration in Wistar rats. This is, to our knowledge, the first attempt to track in vivo the potential internalization of (nano)cellulose fibers. For 21 days, animals were subjected to daily oral gavage of an aqueous suspension 1% (w/v) BNC or of its counterpart of plant origin (Avicel LM310). During the assay, clinical observations, such as body weight measurements, food consumption and ophthalmologic evaluations were performed. After occision, serum chemistry, necropsy examination and histopathological analyses of the liver, kidneys, spleen and small and large intestines were performed. The presence of BNC fibers along the gastrointestinal tract was assessed histologically using a green fluorescence protein coupled to a cellulose carbohydrate binding module (GFP-CBM). No evidence of BNC persorption was found. Particularly, no BNC was detected in the Peyer's patches or in the mesenteric lymphatic nodules. Moreover, the histopathological analyses revealed that the global architecture and morphology of the organs and tissues were preserved, with no significant pathological changes being observed. Regarding serum biochemistry, no significant differences were recorded. These findings suggest that BC nanofibers are not absorbed at the intestine and can be considered a safe food additive.