Fig. 1

Concept of selective CTC-targeting PDT and in vitro blood circulation-mimicking system. a Scheme of the selective CTC-targeting PDT. The CTCs derived from a primary tumor circulate in the blood vessels. Since rose bengals (red circles), which are photosensitizers, were injected intravenously prior to CTC-targeting PDT, rose bengals accumulated inside the primary tumor but also the CTCs. When a 473-nm wavelength laser illuminates the blood vessels, the GFP inside the CTCs activates the rose bengal, which produces singlet oxygen. Singlet oxygen induces the destruction of the CTCs inside the blood vessels. b Scheme of the in vitro fluidic system mimicking blood circulation coupled with laser irradiation. c Proportion of dead cells after irradiation with blue laser light. d Differences in cell death between GFP⁺ (green bar) and GFP⁻ (white bar) NCI-H460 cells after up to three rounds of irradiation with the blue laser light. Blue and red signals indicate Hoechst 33342 and propidium iodide (PI) staining, respectively. Y-axis means the ratio of PI-positive cells to total cells. Error bar means standard deviation. *, P < 0.05; **, P < 0.01; ns, non-specific