Effects of titanium dioxide nanoparticles on intestinal commensal bacteria

Nanomaterials and nanotechnology have great potential in the biological and biomedical field. Recent studies reveal that many nanomaterials possess antibacte- rial activities. While most of these studies focus on the ability of nanomaterials to inhibit the growth of pathogenic bacteria in vitro, few of them test the effects of nanoma- terials on intestinal commensal bacteria. Here, we report that TiO2 nanoparticles （10, 50 and 100 nm in size） can inhibit the growth of Drosophila intestinal commensal bacteria in vitro. This activity depends on the dosage or size, but is independent of the photocatalytic activity of TiO2 nanoparticles. Surprisingly, dietary TiO2 nanoparti- cles of the same dosage fail to display similar effects in Drosophila larvae or adults. These flies show a normal amount of intestinal commensal bacteria, as well as a normal developmental cycle, energy store, and locomotor activity. These results imply that the antibacterial effect of TiO2 nanoparticles differs in vitro and in vivo.