Size Distribution Measurement of Insoluble Particles in PM2.5 Dispersed in Cell Culture Medium Using Aerosolization Techniques

The toxicity of PM_2.5 has attracted interest and has been widely studied because of its adverse health effects. An in vitro assay exposing cultured cells to test particles was used to assess the biochemical response and evaluate PM_2.5 toxicity. The physicochemical properties of PM_2.5 suspensions, particularly particle size distribution, are important parameters that require accurate measurement to reliably assess toxicity. However, the conventional dynamic light scattering method has limited size resolution, making it unreliable for measuring the size distribution of particles with a broad size range. In this study, we present a novel method to accurately measure the size distribution of insoluble particles in PM_2.5 dispersed in a cell culture medium using aerosolization techniques at a submicrometer size range (100 nm to 1000 nm). This method includes sample pretreatment, aerosolization with a spraying device, and size distribution measurements of the aerosolized particles using an electrical mobility analyzing system. Sample pretreatment involves dialysis to remove dissolved nonvolatile components to minimize the formation of residual particles that may interfere with the size distribution measurements of insoluble particles. To validate the method, we measured the size distribution of the monodisperse polystyrene standard particles, including their mixtures, as well as the polydisperse silica standard particles with a known size distribution dispersed in cell culture medium. As a practical application, we demonstrated the measurement of ambient PM_2.5 samples collected from an urban atmosphere and a highway tunnel. Our method provides a novel approach for evaluating the size distribution of insoluble particles in cell culture medium.