Aerosol Generation by a Spray-Drying Technique Under Coulomb Explosion and Rapid Evaporation for the Preparation of Aerosol Particles for Inhalation Tests

Abstract

In this study, nanosized (<100 nm) aerosol particles with high mass concentrations for inhalation tests were generated by a spray-drying technique with combining Coulomb explosion and rapid evaporation of the droplets. Under typical spray-drying conditions, aerosol particles with average diameter of 50-150 nm were prepared from a suspension of NiO nanoparticles with a primary diameter of 15-30 nm. Under the Coulomb explosion method, the sprayed droplets were charged by being mixed with unipolar ions to break up the droplets, which resulted in the generation of smaller aerosol particles with diameters of 15-30 nm and high number concentrations. Under the rapid evaporation method, the droplets were heated immediately after being sprayed to avoid inertial impaction on the flow path due to shrinkage of the droplet, which increased the mass concentration of the aerosol particles. The combination of the Coulomb explosion and rapid evaporation of droplets resulted in the generation of aerosol particles with sizes less than 100 nm and mass concentrations greater than 1 mg/m 3 ; these values are often necessary for inhalation tests. The aerosols generated under the combined method exhibited good long-term stability for inhalation tests. The techniques developed in this study were also applied to other metal oxide nanoparticle materials and to fibrous multiwalled carbon nanotubes.

Pulmonary toxicity of well-dispersed cerium oxide nanoparticles following intratracheal instillation and inhalation

“…The particles were generated from the CeO 2 nanoparticle suspension by the spray-drying method. The details of the experimental setup and conditions were similar to those in our previous study (Shimada et al 2009; Kubo et al 2014). In brief, an aerosol generation system consisting of a pressurized nebulizer and a drying section was connected to a whole body exposure chamber with rat cages.…”

“…Supernatants obtained by a combination of 2 h ultrasonic homogenizing (Branson 5510J-MT, 42 kHz 180 W) and 20,000× g —30 min centrifugation (Hitachi Koki Co., Ltd., CF16RX2) were in stable suspension without agglomerated coarse particles larger than 1 μm. The detailed procedures are explained in our previous report (Kubo et al 2014). The physicochemical properties of CeO 2 nanoparticles are shown in Table 1.…”

In-flight coating of multi-walled carbon nanotubes

“…2b and Supplementary data). This good dispersibility of the MWCNTs was achieved by Coulomb explosions owing to electric charging of the sprayed droplets [14]. In the plasma field, there are various electrons and negative ions that can charge the droplets.…”

Biopersistence of NiO and TiO2 Nanoparticles Following Intratracheal Instillation and Inhalation

“…In the inhalation studies, particles were aerosolized by a nebulizer [39], and the rats were exposed to NiO and TiO 2 nanoparticles in an exposure chamber for 4 weeks (6 h/day, 5 day/week) from age 10 to 13 weeks. Control rats were exposed to fresh air.…”