Alkaline Phosphatase Activated Near-Infrared Frequency Upconversion Photosensitizers for Tumor Photodynamic Therapy

Photodynamic
therapy (PDT) is a promising anticancer method due
to its noninvasive features, high efficiency, and superior accuracy.
The activated near-infrared upconversion photosensitizer has a high
tissue penetration depth and could be explicitly released with minimal
side effects. Therefore, we designed and synthesized a series of Br-substituted
compounds (NFh-Br) based on the near-infrared upconversion hemicyanine
dye. The heavy atomic effect improves the generation of 1O2 and upconversion luminous efficiency. Especially, NFh-Br11 exhibited an excellent 1O2 generation
rate under 808 nm excitation and effectively killed tumor cells in
vitro, and the alkaline phosphatase (ALP)-activatable photosensitizer
(NFh-ALP) was obtained by modifying the NFh-Br11. NFh-ALP
could be activated by ALP and release NFh-Br11, which induces
apoptosis of tumor cells and has outstanding anticancer effects in
vitro and in vivo. This work could provide a strategy for designing
activatable upconversion photosensitizers.