652632.fig.001a
(a)   ALI condition
652632.fig.001b
(b) Submerged condition
Figure 1: Schematic of the two cell exposure models used for studying particle-cell interaction. (a) Exposure at the air-liquid interface (ALI): airborne particles are directly deposited on cells grown at the air-liquid interface. (b) Exposure under submerged conditions: particles were suspended directly in the cell culture medium covering the cells.