Generating Nano-Aerosols from TiO₂ (5 nm) Nanoparticles Showing Different Agglomeration States. Application to Toxicological Studies

Abstract

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 (5 nm) NP showing different agglomeration states. Two concentrations were tested: 2 and 7 mg/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 (<100 nm), while aerosols composed of larger agglomerates (>100 nm) 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 185 nm, respectively, for the 2 mg/m³ concentration, and 31 and 194 nm for the 7 mg/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.

Keywords:

• characterization
• inhalation
• nano-aerosol generation
• nanotoxicology
• TiO₂ nanoparticles

ACKNOWLEDGMENTS

Special thanks are expressed to Annie Ouellet of the Institut de recherche Robert-Sauvé en santé et en sécurité du travail (IRSST) for her technical support.

This work was supported by a grant from the Quebec Center for Asthma in the Workplace and was also a collaborative multi-disciplinary research initiative in the Axe de recherche en nanotoxicologie of the Réseau de recherche en santé et en sécurité du travail du Québec (RRSSTQ). Alexandra Noël is a recipient of doctoral scholarships from the Institut de recherche Robert-Sauvé en santé et en sécurité du travail (IRSST) and from the Fonds de la recherche en santé du Québec (FRSQ). The authors declare that they have no conflict of interest.