General Safety References
“Different crystalline forms of TiO2 nanoparticles have different reactivities and can differ in their toxicity despite having the same chemical composition. Anatase crystals of TiO2 are more UV-active than the rutile crystals of TiO2, resulting in the cytotoxic potency of anatase crystals being far greater than the rutile form1. The UV photoactivity of metal oxide nanoparticles can be altered by adding ‘dopants’ into their crystalline structure. Also different particle sizes and surface modification of metal and metal oxide nanomaterials like silver and gold nanoparticles, can alter their internalisation after binding to cells, and the subsequent in vitro cytotoxicity2. For example, Uboldi et al. (2008) recently found that surface modification of gold nanoparticles (5-25 nm) with sodium citrate impaired cell viability and proliferation greater than unmodified nanoparticles, in human alveolar type-II cell lines exposed in vitro.3
For specific information, see:
1. Sayes CM, Liang F, Hudson JL, Mendez J, Guo W, Beach JM, Moore VC, Doyle CD, West JL, Billups WE, Ausman KD & Colvin VL, “Functionalization density dependence of single-walled carbon nanotubes cytotoxicity in vitro” Toxicol Lett. 161(2), 135-42 (2006).
2. Jiang W, Kim BYS, Rutka JT & Chan WCW, “Nanoparticle-mediated cellular response is size-dependent,” Nature Nanotechnology 3 (March 2008), 145-150..
3. Uboldi C, Barth S, Unger RE & Kirkpatrick JC, “Surface modification influences the in vitro toxicity of gold nanoparticles in human alveolar type-II cell lines,” Alternatives to Animal Experimentation (ALTEX) 2008, 25 (Suppl. 1), 74 (accessed 6 Oct. 2008) (copyright Commonwealth of Australia, reproduced by permission).