Fig. 4.

Microengineered model of pulmonary nanotoxicology. (A) Ultrafine silica nanoparticles introduced through an air-liquid interface overlying the alveolar epithelium induce ICAM-1 expression (red) in the underlying endothelium and adhesion of circulating neutrophils (white dots) in the lower channel (bar, 50 μm). Graph shows that physiological mechanical strain and silica nanoparticles synergistically upregulate ICAM-1 expression (*p < 0.005; **p < 0.001). (B) Alveolar epithelial cells increase ROS production when exposed to silica nanoparticles (100 μg/ml) in conjunction with 10% cyclic strain (square) (p < 0.0005), whereas nanoparticles (triangle) or strain (diamond) alone had no effect on intracellular ROS levels relative to control cells (circle); ROS generation was normalized to the mean ROS value at time 0. (C) The alveolar epithelium responds to silica nanoparticles in a strain-dependent manner (*p < 0.001). (D) Addition of 50 nm superparamagnetic nanoparticles produced only a transient elevation of ROS in the epithelial cells subjected to 10% cyclic strain (p < 0.0005). (E) Application of physiological mechanical strain (10%) promotes increased cellular uptake of 100 nm polystyrene nanoparticles (magenta) relative to static cells, as illustrated by representative sections (a-d) through fluorescent confocal images. Internalized nanoparticles are indicated with arrows; green and blue show cytoplasmic and nuclear staining, respectively. (F) Transport of nanomaterials across the alveolar-capillary interface of the lung is simulated by nanoparticle transport from the alveolar chamber to the vascular channel of the lung mimic device. (G) Application of 10% mechanical strain (closed square) significantly increased the rate of nanoparticle translocation across the alveolar-capillary interface compared to static controls in this device (closed triangle) or in a Transwell culture system (open triangle) (p < 0.0005). (H) Fluorescence micrographs of a histological section of the whole lung showing 20 nm fluorescent nanoparticles (white dots, indicated with arrows in the inset at upper right that shows the region enclosed by the dashed square at higher magnification) present in the lung after intratracheal injection of nebulized nanoparticles and ex vivo ventilation in the mouse lung model. Nanoparticles cross the alveolar-capillary interface and are found on the surface of the alveolar epithelium, in the interstitial space, and on the capillary endothelium (PC, pulmonary capillary; AS, alveolar space; blue, epithelial nucleus; bar, 20 μm). (I) Physiological cyclic breathing generated by mechanical ventilation in whole mouse lung produces more than a 5-fold increase in nanoparticle absorption into the blood perfusate when compared to lungs without lung ventilation (p < 0.0005). The graph indicates the number of nanoparticles detected in the pulmonary blood perfusate over time, as measured by drying the blood (1 μl) on glass and quantitating the number of particles per unit area (0.5 mm²). (J) The rate of nanoparticle translocation was significantly reduced by adding NAC to scavenge free radicals (*p < 0.001).