Fig. 4

In vitro fluorescent “off–on” switch and antitumor activity of GQDs/Cy5-miR@sEVs. A The fluorescence images showing the uptake of FAM-miR-GQDs@sEVs by HGC-27 cells at 1, 2, and 4 h. GQDs (blue), FAM-tagged miRNA (green) and nuclei (red) were shown, where scale bar = 100 μm. B FAM-miRNA (green) successfully escaped from endosomes (red) as evidenced by the separation of green and red fluorescence (indicated by arrows). Endosome/lysosome and nuclei were stained with Lysotracker Red and DAPI, respectively. Scale bar = 20 μm. C MiR-193a-3p was detected in HGC-27 cells by qRT-PCR after they were treated with GQDs/Cy5-miR and GQDs/Cy5-miR@sEVs. D Target gene CCND1 was detected in HGC-27 cells by qRT-PCR after they were treated with sEVs, GQDs/Cy5-miR and GQDs/Cy5-miR@sEVs, respectively. E Protein expression of CCND1 in HGC-27 cells by Western blot after being treated with PBS, GQDs, sEVs, GQDs/Cy5-miR, and GQDs/Cy5-miR@sEVs, respectively. F Western blot was used to detect the protein level of PCNA, Bax, Bcl-2, cleaved caspase-3 as well as β-actin proteins in HGC-27 cells. G Viability of HGC-27 cells and H viability of HUVEC cells were determined by CCK-8 assay. I Cell colony formation assays of HGC-27 cells when treated in different conditions as indicated. Data are expressed as mean ± SD and analyzed by one-way ANOVA. ns, no significance; *p < 0.05, **p < 0.01, ***p < 0.001, ****p < 0.0001