Fig. 5.
FIB-SEM micrographs of both types of CNTs in the lung samples. a–b The CNTSmall sample imaged with standard milling including a platinum layer, where it can be difficult to discern CNTs from cellular material. Black arrowheads mark the likely agglomerations of CNTs not observed in control samples and correlated with CNTs protruding from the surface of the Epon block. One cell appears to have a large invagination, possibly containing CNTs (small white arrowheads). c–d CNTLarge samples obtained via standard milling, but without protective platinum layer. Here, the milling artefacts (vertical white lines) caused by surface roughness is clearly seen (especially in c). However, the cells and CNTs are still visible, and single CNTs can be found to interact closely with the tissue, but are only in very few cases observed to appear entering the alveolar wall (white arrowheads in d). e–f FIB-SEM of CNTLarge using the double non-tilted milling approach limiting surface roughness caused artefacts, with arrowheads highlighting the protruding CNTs caused by differing milling yields. f SEM image obtained from the viewpoint of the ion beam, showcasing that CNTs protrude from the milled surface. A alveoli, E erythrocyte, L lamella body, M mitochondrion, N nucleus, and P2 pneumocyte (type 2)