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Wang et al. Cancer Drug Resist. 2026;9:8 Page 9 of 18

Figure 2. Cellular accumulation of PTTP-DCns. (A) Flow cytometric analysis of the cellular uptake of PTTP-DCns in MCF-7/ADR cells
after a 2-hour incubation; (B) Confocal images of MCF-7/ADR cells stained with PTTP-DCns molecules after 24-hour incubation; (C)
Representative merged images showing the co-localization of PTTP-DCns (red) and lysosome-specific dye LysoTracker Green (green) in
MCF-7/ADR cells; (D and E) Confocal images and corresponding quantitative analysis (one-way ANOVA with Tukey’s test, P < 0.001)
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of MCF-7/ADR cells incubated with PTTP-DC6 (1 µM) in the presence of various endocytosis inhibition conditions; (F and G) Confocal
images and corresponding quantitative analysis (Student’s t-test, P < 0.001) of MCF-7/ADR cells pre-treated with MβCD (10 mM) for
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30 min and then incubated with PTTP-DC6 (10 µM) at 37 °C for 2 h. Scale bar: 10 μm. Data presented as mean ± SD. PTTP-DCns:
Benzene-pyridothiadiazole-thienothiophene-pyridothiadiazole-benzene conjugated framework with quaternary ammonium-terminated
n-carbon alkyl chains at both ends; MCF-7/ADR: Michigan Cancer Foundation-7/adriamycin-resistant; ANOVA: analysis of variance;
PTTP-DC4/6/8: benzene-pyridothiadiazole-thienothiophene-pyridothiadiazole-benzene conjugated framework with quaternary
ammonium-terminated C4/C6/C8 alkyl chains at both ends; PCC: Pearson’s correlation coefficient; MβCD: methyl-β-cyclodextrin; SD:
standard deviation; FL: fluorescence; Dyn: dynasore; CPZ: chlorpromazine; Gen: genistein.

[Figure 2F and G]. Hence, the slightly reduced PTTP-DC6 uptake by caveolae inhibitor Gen is probably a
result of Gen-induced reduction of membrane fluidity .
[35]
Subsequently, the biosafety of PTTP-DCns towards cells was estimated via MTT assay. As shown in Figure
3A and Supplementary Figure 10, PTTP-DCns showed no significant dark toxicity to cancer cell line

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