Figure 2. Double-staining with Hoechst and propidium iodide (PI). The images in the left column show the total number of cells stained with Hoechst, the middle column shows the cells with positive staining for PI, and the right column shows the merged images. Control cells (A-C) exhibited no double-staining. Positive control group cells (incubated with 50 µg/mL digitonin; D-F) showed a large number of double-labeled cells, indicating that the method was effective. Treatments with sodium hyaluronate (HY; G-I), single-walled carbon nanotubes (SWCNT; J-L), and HY-functionalized SWCNT (HY-SWCNT; M-O) did not affect cell viability, which was confirmed by morphometric analysis (P). *P<0.05 compared to control, HY, HY-SWCNT, and SWCNT (one-way ANOVA followed by Newman-Keuls post-hoc test). Scale bar = 100 µm.