Fig. 7. Bright-field (left) and dark-field (right) microscopy images of an A549 cell line after 4 h incubation in a medium containing (a) Au50s, (b) Au40s, (c) Au25s, (d) Au10s, and (e) control. AuNR images at a concentration of 1 × 10¹¹ NP ml⁻¹ for each AuNR type. All dark-field microscopy images are presented using the same brightness and contrast conditions. Scale bar = 20 μm.