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. 2019 Jan 25;9(4):961–973. doi: 10.7150/thno.30765

Figure 5.

Figure 5

Intracellular DOX release from ACC-DOX-SF NPs. (A) Time-dependent (2 h, 6 h, and 12 h) intracellular uptake of ACC-DOX-SF NPs at pH 6.5 as observed by CLSM. (B) Viability assay of ACC-SF NPs incubated with HUVECs for 20 h at various concentrations. (C) Cytotoxicity assay of free DOX, ACC-DOX-SF NPs at pH 7.4, and ACC-DOX-SF NPs at pH 6.5 incubated with 4T1 cells for 24 h at different concentrations. The results are expressed as the mean ± SD, *P < 0.05, **P < 0.01, or ***P < 0.001. (D) Free DOX and ACC-DOX-SF NPs colocalized with lysosome tracker at different pH values (pH 7.4 and pH 6.5) as observed by CLSM after 3 h. For each panel, lysotracker stained the endolysosome (green); DAPI stained cell the nucleus (blue); DOX indicates NPs or drugs; and white arrows indicate NPs/ DOX located with/outside the endolysosomes, suggesting that ACC could also decompose in the cytoplasm. (E) TEM of 4T1 cells incubated with ACC-DOX-SF NPs for 4 h. The ROI (yellow square in the image) demonstrates the explosion of lysosome-targeted NPs. N, nucleus; M, mitochondria; ER, endoplasmic reticulum; L, lysosomes; MF, myelin figure.