Stable metal oxide nanoparticle formulation for toxicity studies.

Metal oxide nanoparticles such as TiO2 (< 100 nm) are used in lotions and sunscreens. Toxicity studies so far have reported the use of TiO2 NPs with size > 100 nm as determined by dynamic light scattering (DLS) technique. We used non-reactive chemical agents such as propylene glycol (PG), glycerol (G), ethylene glycol (EG) to prevent aggregation and maintain NPs in monodispersed state closer to the reported TEM size. The lowest concentration of PG (0.1%) along with complete culture media (RPMI 1640) showed mean hydrodynamic diameter of TiO2 NPs as 33.71 nm measured by DLS. The present study demonstrates a method to prepare stable TiO2 NPs in culture media for toxicity assessment. This is a significant contribution as the biological properties of NPs vary considerably with decrease in size.