Generating nano-aerosols from TiO₂ (5 nm) nanoparticles showing different agglomeration states. Application to toxicological studies.

Agglomeration of nanoparticles (NP) is a key factor in the generation of aerosols from nano-powders and may represent an important parameter to consider in toxicological studies. For this reason, the characterization of NP aerosols (e.g., concentration, size, and structure of agglomerates) is a critical step in the determination of the relationship between exposure and effects. The aim of this study was to generate and characterize aerosols composed of TiO2 (5nm) NP showing different agglomeration states. Two concentrations were tested: 2 and 7mg/m3. Stable mass concentrations over 6 hr were successfully generated by a wet method using Collison and Delavan nebulizers that resulted in aerosols composed of smaller agglomerates (<100nm), while aerosols composed of larger agglomerates (>100nm) were obtained by dry generation techniques using either a Palas dust feeder or a Fluidized Bed. Particle size distributions in the aerosols were determined by an electrical low pressure impactor. Median number aerodynamic diameters corresponding to the aerosol with smaller and larger agglomerates were 30 and 185nm, respectively, for the 2mg/m3 concentration, and 31 and 194nm for the 7mg/m3 experiment. Image analysis by transmission electron microscopy showed the presence of compact or agglomerates with void spaces in the different nano-aerosols. These characterized nano-aerosols will be used in further experiments to study the influence of agglomerate size on NP toxicity.