Fig. 4

a Representative image of U87 spheroid using a light microscope. b Representative image of U87 spheroid using fluorescence microscope after incubation for 4 h with 10 µM Ce6 and staining the nuclei with Hoechst 33258. c Representative light microscope image of U87 spheroid treated with Ce6-PDT on day 0. d Representative light microscope image of U87 spheroid treated with Ce6-PDT on day 3. e Fold increase of U87 spheroid projected area monitored over 5 days after incubation for 4 h with 10 µM Ce6 followed by 2.4 J/cm² irradiation using 665 nm compared to the dark control group in which spheroids were only incubated with 10 µM Ce6 without irradiation. Spheroids were imaged using 10 × magnification. Experiments were repeated at least 3 times and presented are mean and standard deviation