Fig. 6

Confocal microscopy images of 3D tumor spheroids of MCF-7 cells after a 24 h incubation with D-L at pH 6.5 and 7.4. a Penetration of D-L in MCF-7 tumor spheroids. Z-stack images were obtained from the top to the equatorial plane. Each scanning layer was 8 µm thick, and the total scan depth was 64 µm. b 3D reconstruction of all scanned layers. The FAM-siRNA and DiD concentrations were 400 nM and 1.33 μg mL⁻¹, respectively. FAM-siRNA fluorescence (green) and DiD fluorescence (red) were recorded