Fig. 2. Impact of Buthionine Sulfoximine on TPPS_2a-mediated Photodynamic Therapy. 4T1 breast cancer cells treated with TPPS_2a, 0.6 μg ml⁻¹, alone. (A) Cells illuminated immediately after TPPS_2a washed off, with (blue line) or without (black line) BSO, 1.0 μg ml⁻¹; (B) cells illuminated 4 h after TPPS_2a washed off, with (orange broken line) or without (black broken line) BSO, 1.0 μg ml⁻¹. Cells were illuminated up to 300 s. Cell viability was measured using the MTT assay, 24 h after illumination. Significant cell kill (P < 0.01) was shown for all groups >150 s illumination in 2B.