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Published on: May 26, 2023
In vitro toxicity evaluation of food-grade silica nanoparticles (E551) in human digestive tract cells
Beatriz Roquett1,2, Diego Wiechers1,3, Ana Júlia Fagundes1
1Laboratory of Eukaryotic Cell Biology (Labio), National Institute of Metrology, Quality and Technology (INMETRO), Rio de Janeiro, Brazil.
Abstract:
Synthetic amorphous silica (SAS, E551) is one of the most widely used food additives, yet uncertainties remain regarding the potential biological effects of its nanoscale fraction. In this study, we performed a metrologically aligned in vitro assessment of food-grade SAS nanoparticles (NPs) in human digestive tract cell models. Detailed physicochemical characterization confirmed their amorphous structure and high purity (EDS, XRD), while dispersion protocols generated two size distributions: ultrasonication (Dispersion A, ~ 238-299 nm) and stirring (Dispersion B, ~ 1300-1600 nm). Dynamic light scattering (DLS) revealed colloidal instability in culture media, with zeta potential decreasing from - 26 mV (water) to ~-9 mV (DMEM). Human colorectal epithelial cells (Caco-2) and gingival fibroblasts (HGF) were exposed to 19.8-200 µg/mL SAS for 72 h. Cell viability remained above 75% in MTT assays, and real-time impedance (xCELLigence) confirmed stable proliferation curves comparable to controls. No increase in intracellular reactive oxygen species was observed, although transmission electron microscopy revealed endocytic uptake with particles confined to cytoplasmic vesicles. Cytokine analysis showed only discrete, dose-dependent modulations, with an increase in MCP-1 (HGF) and VEGF (Caco-2) only at the lower concentration. Scanning electron microscopy (SEM) demonstrated concentration-dependent ultrastructural changes, ranging from elongation of microvilli at 19.8 µg/mL to disorganization of the apical surface at 200 µg/mL. These findings indicate that food-grade SAS does not induce acute cytotoxicity under the tested conditions but can trigger sub-cytotoxic and adaptative morphological and secretory alterations in gastrointestinal cells. Our results emphasize the critical role of dispersion protocols in nanotoxicology and support evidence-based regulation of E551, highlighting the need for chronic and immunological studies to refine its safety profile.
Supplementary Information:
The online version contains supplementary material available at 10.1007/s44164-025-00101-x.
