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 [Hf6O4(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. 1.2nm) enable highly effective X-PDT to afford superb anticancer efficacy.