Fig. 3. (A) CLSM images of 4T1 cells treated with MSN@U/DCNPs under different pH conditions. (B) The intracellular Gd amount of 4T1 cells exposed to different concentrations of MSN@U/DCNPs at pH 6.5 and 7.4. (C) Tumor penetration of MSN@U/DCNPs in 4T1 MCSs at pH 6.5 and 7.4 observed by Z-stack CLSM. (D, E) 2.5D fluorescence and (F) line intensity analysis of the CLSM images at a 90 μm depth.