Near-infrared-responsive nanoplatforms integrating dye-sensitized upconversion and heavy-atom effect for enhanced photodynamic therapy efficacy

The development of near-infrared (NIR)-responsive upconversion nanoplatforms for photodynamic therapy (PDT) has attracted considerable attention in recent years, but is still limited by the low PDT efficacy. Herein, we designed and synthesized a NIR-responsive nanoplatform through the integration of lanthanide-doped upconversion nanoparticles (UCNPs), Pt-decorated porphyrin metal-organic frameworks (PMOFs) and NIR dye IR808 into a core-shell structure for highly efficient antibacterial PDT. The PMOF shell can function not only as a photosensitizer to absorb the upconversion luminescence (UCL) of UCNPs for singlet oxygen (O-1(2)) generation, but also as a porous host material for loading of IR808. Remarkably, we demonstrated that the heavy-atom effect of Pt(II) can simultaneously enhance the intersystem crossing (S-1 -> T-1) efficiencies of the IR808 and the porphyrin ligand Pt-TCPP, resulting in the enhancement of dye-triplet-sensitized UCL of UCNPs and O-1(2) production capacity of the photosensitizer. As a result, the proposed nanoplatform exhibited excellent O-1(2) production and a significant bactericidal activity against methicillin-resistant Staphylococcus aureus (MRSA) with 5.27 log(10) (> 99.999%) killing efficacy. These findings will pave the way for designing highly efficient PDT nanoplatforms and accelerate their biomedical applications.