Nanoscale Metal-Organic Layers for Deeply Penetrating X-ray-Induced Photodynamic Therapy

We report the rational design of metal-organic layers (MOLs) that are built from [Hf₆ O₄ (OH)₄ (HCO₂ )₆ ] secondary building units (SBUs) and Ir[bpy(ppy)₂ ]⁺ - or [Ru(bpy)₃ ]²⁺ -derived tricarboxylate ligands (Hf-BPY-Ir or Hf-BPY-Ru; bpy=2,2'-bipyridine, ppy=2-phenylpyridine) and their applications in X-ray-induced photodynamic therapy (X-PDT) of colon cancer. Heavy Hf atoms in the SBUs efficiently absorb X-rays and transfer energy to Ir[bpy(ppy)₂ ]⁺ or [Ru(bpy)₃ ]²⁺ moieties to induce PDT by generating reactive oxygen species (ROS). The ability of X-rays to penetrate deeply into tissue and efficient ROS diffusion through ultrathin 2D MOLs (ca. 1.2 nm) enable highly effective X-PDT to afford superb anticancer efficacy.