Toxicity Of Food Additive Silica Nanoparticles To Gastrointestinal Cells

Silica particles produced by aerosol and precipitation methods, have beenwidely applied in food products as additive. It is mainly used as an anticaking agentto maintain flow properties of powdered products. Along with the development ofsynthesis methods, silica particles become nano-sized. However, at present the safetystudies of silica nanoparticles （nano-SiO₂） focus on the pulmonary toxicity in theview of occupational exposure, the safety data of nano-SiO₂as food additive isscarce. Considering food additive nano-SiO₂enters body along with food throughoral administration, and gastrointestinal tract will be the most important absorptionsite, a comprehensive study was performed to evaluate the toxicity of food additivenano-SiO₂to gastrointestinal cells.Firstly, four food additive silica samples were purchased from differentcompanys with food additive licenses. A comprehensive characterization was givenby TEM, XRF, XRD, FT-IR, DLS and BET techniques. The four food additivenano-SiO₂samples were amorphous and nano-sized, with a primary size of10-50nm. These particles had hydroxyl groups and negative charges on surface andaggreageted heavily in aqueous.Subsequently, a systematic sudy was performed on the toxicity of these four foodadditive nano-SiO₂on two gastrointestinal cells, the human gastric epithelial cellGES-1and the human colorectal adenocarcinoma cell Caco-2. Generally, low doseof nano-SiO₂was safe for human being. We found that nano-SiO₂affected cellviabilities in a time-and dose-and sample-dependent manner. Although they did notresult in cell membrane damage, change the cell morphology, decrease themitochondrial membrane potential and increase apoptosis/necrosis of cells, they didenter cells, induce slight ROS generation, and inhibited the cell growth by blockingcells in S phase. The GES-1cells were more sensitive than the Caco-2cells to thesenano-SiO₂. No translocation of nano-SiO₂across Caco-2cell monolayer indicated it may be difficult for nano-SiO₂to pass through the intestinal wall.In addition, the gastrointestinal toxicity of nano-TiO₂particles separated fromgum was studied. We found that these nano-TiO₂particles were safey under ourexperimental conditions.The results obtained in this thesis are essential for the biosafety assessment offood additives nanoparticles.