A lysosome-targeted near-infrared photosensitizer for photodynamic therapy and two-photon fluorescence imaging

Organelle-targeted two-photon near-infrared photosensitizers are highly desirable for photodynamic therapy (PDT) of cancer. Herein, in this contribution, we have developed a 2-dicyanomethylenethiazole-based D-pi-A structured near-infrared photosensitizer (TTR). TTR exhibits near-infrared emission (704 nm), a large Stokes shift (200 nm), and smaller Delta E-S1-(T1) (the energy gap between S-1 and T-1) (0.717 eV). In vitro results show that TTR can specifically target lysosomes in living cells for near-infrared fluorescence imaging. With efficient ROS generation, excellent biocompatibility, two-photon imaging capability, and depth imaging (21 mu m in vitro and 210 mu m in vivo), TTR can effectively kill tumor cells and inhibit the growth of subcutaneous tumors. The hematoxylin-eosin (H&E) staining and blood biochemical parameter results further prove the biocompatibility of TTR. Hence, TTR can be a promising photosensitizer for PDT.