Fig. 4
From: Photosensitizing deep-seated cancer cells with photoprotein-conjugated upconversion nanoparticles
NIR-induced ROS generation of UCNP-KR-LP in cancer cells. a−b Detection of superoxide (O2•−) generation by CS-UCNPs (a) and Co-UCNPs (b) based on the DHE bleaching effect. The bleaching effects of the control (no NP), unmodified NP (CS-UCNP or Co-UCNP), and modified NP (CS-UCNP-KR-LP or Co-UCNP-KR-LP) groups were examined in the absence and presence of NIR irradiation over time (10−30 min). c Effect of different ROS scavengers on superoxide generation. CS-UCNP-KR-LP was treated with three ROS scavengers (SOD, sodium azide, and mannitol) after NIR irradiation for 30 min. The significant difference among scavengers was evaluated (***P < 0.001, n = 3, one-way ANOVA with post-hoc Tukey’s test). d−e Quantitative FACS analysis of intracellular ROS generation in DCFDA-responsive MCF-7 cell populations after treatment with unmodified or modified UCNPs (with KR or KR-LP). DCFDA was added to the cell culture medium before NIR irradiation at 980 nm. f Representative confocal images of intracellular ROS signals detected using DCFDA (green) in MCF-7 cells after treatment with unmodified or modified UCNPs (with KR or KR-LP). Experimental conditions were similar to those of FACS. White scale bar = 120 μm. g Quantitative FL analysis of DCFDA intensity from confocal images in three independent experiments. DHE, dihydroethidium; SOD, superoxide dismutase, FACS, fluorescence-activated cell sorting; DCFDA, 2ʹ,7ʹ-dichlorofluorescein diacetate