Delivery efficiency and cell viability testing. (a-d) Delivery of calcein to HeLa cells using gold nanodisk arrays (1 μm wide, 2 μm pitch, 30 nm thickness) under laser irradiation with 11 mJ/cm2 fluence. (a) Representative image of delivery of calcein (green) to targeted cells. (b) Cell nuclei are stained with Hoechst 33342 to label both live and dead cells (blue). (c) Propidium iodide (PI) assay to identify dead cells (red). (d) Overlaid image of calcein, Hoechst 33342, and PI dyes. Efficiency was found to be 98 ± 1%, and viability is 99 ± 1%. (e–h) Control experiment using flat gold thin film under the same laser irradiation of 11 mJ/cm2 fluence, where (e) corresponds to the calcein channel, (f) is the Hoechst dye, (g) is the PI dye, and (h) is the overlaid image of (e–g). Scale bars: 100 μm.