Fig. 4.

Increased cellular uptake (serum‐starved condition) of isolated EVs secreted under low pH cell culture condition. (A) Confocal microscopic observation of A431 cells treated with isolated CD63‐GFP‐EVs [20 μg·mL⁻¹ for 48 h at 37 °C in MEM (pH 7) without FBS], secreted under pH 7 or pH 5 cell culture condition. Blue signals, Hoechst 33342 for nuclear staining; green signals, CD63‐GFP‐EVs. Scale bar, 20 μm. (B) The relative cellular uptake of isolated CD63‐GFP‐EVs [20 μg·mL⁻¹ for 48 h at 37 °C in MEM (pH 7 or 5) without FBS] secreted under pH 7 or pH 5 cell culture condition, analyzed using a flow cytometer (detection for 10 000 live cells). The data are expressed as the mean (± SD) of three experiments. Differences between groups were compared by two‐way ANOVA followed by Bonferroni's post hoc test ***P < 0.001, ****P < 0.0001.