A photo-stable and reversible pH-responsive nano-agent based on the NIR phenazine dye for photoacoustic imaging-guided photothermal therapy.

Different from traditional "always on" photothermal therapy (PTT) agents, tumor microenvironment responsive agents showed more tumor specificity and lower photo-toxicity to normal tissues. Herein, a photo-stable and reversible pH responsive phenazine dye (PIOH) was synthesized and assembled with liposomes forming nanoparticles (PIOH-NPs), which exhibited a strong NIR absorption in a weak acid environment and were successfully utilized for photoacoustic (PA) imaging-guided photothermal therapy in mice.