Background and Objectives: Toxicity assessment of material related to nanotechnology is necessary before excess development of this industry. On the other hand, specific characteristic of nanomaterials can be used in disinfection of other material. In this study toxicity and antibacterial properties of nano-TiO₂ and nano-CuO were investigated with four bacterial species in solid media.

Material and Methods: Stock suspension of nanoparticles (10g-TSS/L) was diluted using Muller Hinton Agar to achieve 5-6000mg-TSS/L concentration. We prepared three Petri dishes for each concentration and refined bacteria were cultured on these Petri dishes. After culturing of these bacteria on the media containing nanoparticles, growth inhibition was determined. According to this data, 50% growth inhibition (EC₅₀), no observed effect concentration (NOEC) and 100% growth inhibition were determined.

Results: Our results showed that toxicity of TiO₂ is more than CuO in solid media. In this regard, nano-TiO₂ EC₅₀ for Escherichia coli, Bacillus subtilis, Staphylococcus aureus, and Pseudomonas aeruginosa was calculated 181, 571, 93 and 933mg-TSS/L respectively. These figures for nano-TiO₂ were 2550, 1609, 946, and 1231mg-TSS/L respectively.

Conclusion: This study showed that compared with other bacteria studied, E. aureus due to high sensitivity and E. coli due to high resistance to both TiO₂ and CuO nanoparticles are more proper as bioindicator in toxicity test and antibacterial test respectively.