Fig. 5A depicts the quantification of internalised fluorescence-labelled NPs (Sicastar Red: 6 μg/ml, AmOrSil: 300 μg/ml) in H441 for 4 h with further 20 h cultivation in MC and CC (with ISO-HAS-1). Concentrations were chosen to obtain adequate fluorescence intensities in order to compare mono- and cocultures. A significant increase in fluorescence intensity was observed for NP-incubated H441 in MC for both NPs (Fig. 5A: Sicastar Red: 1.5 ± 0.5-fold of uc and AmOrSil: 2.7 ± 0.3-fold of uc). For H441 in CC, however, an uptake via fluorescence

intensity measurement could not be detected. Based on the visual examination of the microscopic image buy Erlotinib (Fig. 5B), the uptake of both NP types in H441 in CC appeared extremely low compared to

the MC. In Fig. 5C, an elevation of the NP-concentration and exposure time revealed an increased uptake of Sicastar Red (60 μg/ml, Selumetinib mouse 48 h) in H441 in CC. However, an increased uptake of AmOrSil (300 μg/ml, 48 h) could not be verified. The same exposure times and staining procedures as described above (see Fig. 2) were carried out with H441 grown in CC with ISO-HAS-1 to determine if differences in nanoparticle uptake or trafficking behaviour from H441 under different culture conditions compared to the MC occurred. Although the monoculture of H441 showed fluorescent signals inside the cells after only 4 h of incubation, this time period yielded no uptake in H441 in CC with both NP types as detectable by fluorescence microscopy (data not shown). Similar to the findings in the MC, no clear uptake in early endosomes (clathrin heavy chain, caveolin-1 and other markers) was detected in the CC at all time points chosen (4 h and 4 h followed by 20 h cultivation in fresh medium without NPs).

Accumulation of Sicastar Red in flotillin-1- and -2-bearing vesicles occurred after 20 h following the 4 h incubation period (Fig. 6) similar to that observed in MC. AmOrSil however, did not show any colocalisation with flotillin-1 and 2 (data not shown). Fig. 7 (left column) shows exposure of ISO-HAS-1 in MC to NPs as it was applied for the colocalisation studies (Sicastar Red 6 μg/ml and AmOrSil: 300 μg/ml, 4 h with 20 h cultivation in serum-containing medium without NPs. A detectable uptake could be verified with direct exposure to NPs for Casein kinase 1 the MC. To evaluate the transport of NPs across the NP-exposed epithelial layer of the CC, the endothelial layer (ISO-HAS-1) on the lower surface was examined for NPs. For this purpose, NPs (Sicastar Red: 60 μg/ml, AmorSil: 300 μg/ml) were continuously applied on the apical side (on the epithelial monolayer of H441) for 48 h. As a control ISO-HAS-1 was seeded on the lower surface of the transwell filter membrane and cultured for 10 days with subsequent indirect (apical) NP-application without H441 on the top (Fig. 7, middle column). A cellular uptake of both NPs could be detected in the ISO-HAS-1 transwell-monoculture.