Biomimetically constructing a hypoxia-activated programmable phototheranostics at the molecular level.

The hypoxic microenvironment is considered the preponderant initiator to trigger a cascade of progression and metastasis of tumors, also being the major obstacle for oxygen consumption therapeutics, including photodynamic therapy (PDT). In this work, we report a programmable strategy at the molecular level to modulate the reciprocal interplay between tumor hypoxia, angiogenesis, and PDT outcomes by reinforcing synergistic action between a HO scavenger, O generator and photosensitizer. The modular combination of a catalase biomimetic (tri-manganese cryptand, 1) and a photosensitizer (Ce6) allowed the rational design of a cascade reaction beginning with dismutation of HO to O under hypoxic conditions to enhance photosensitization and finally photooxidation. Concurrently, this led to the decreased expression of the vascular endothelial growth factor (VEGF) and effectively reduced unwanted growth of blood vessels observed in the chick chorioallantois membrane (CAM). Notably, the proof-of-principle experiments using the tumor-bearing models proved successful in enhancing PDT efficacy, prolonging their life cycles, and improving immunity, which could be monitored by magnetic resonance imaging (MRI).