Toxicity Assessment of SiO2 and TiO2 in Normal Colon Cells, In Vivo and in Human Colon Organoids.

We conducted systemic assessments on the toxicity of silicon dioxide (SiO2) and titanium dioxide (TiO2) nanoparticles using different forms of normal colon cells (CCD-18Co), in vivo and in human colon organoids. The in vivo acute oral toxicity data showed that the LD50 values are greater than 2000 mg/kg for both the SiO2 and TiO2 nanoparticles; however, the SiO2 and TiO2 nanoparticles induced cytotoxicity in two-dimensional CCD-18Co cells and three-dimensional CCD-18Co spheroids and human colon organoids, with IC50 values of 0.6, 0.8 and 0.3 mM for SiO2 and 2.5, 1.1 and 12.5 mM for TiO2 nanoparticles, respectively. The data suggest that, when SiO2 and TiO2 are in nanoparticle form, cytotoxicity is induced; thus, care should be taken with these materials.