Upconversion luminescence mediated photodynamic therapy through hydrophilically engineered porphyrin

Photodynamic therapy that involves the photosensitizer transferring the absorbed energy to surrounding tissue oxygen has been used in clinical treatment of cancer. However, the clinically used porphyrin derivatives as PDT photosensitizers usually need high energy excitation light, which generally gives rise to limited tissue penetration depth and thereby limited photoactivation efficiency. Herein, protoporphyrin IX was chemically modified by jeffamines for improving the hydrophilicity and biocompatibility, and the resulting water-soluble porphyrin-jeffamine (PJ) was further covalently conjugated to the PEGylated upconversion nanoparticles (UCNPs) via “click” reaction, which is an efficient way to precisely control the resonance energy transfer from UCNPs to PJs. Our work demonstrates that, the probes can be effectively photosensitized to produce reactive oxygen species (ROS) under the excitation of 980 nm NIR light. When compared with the clinically used photosensitizer molecules, the probes exhibit a comparable capability for producing ROS. Besides, the probes present an outstanding ability in targeting tumor cells and high efficiency in inducing cell death through the photoactivation by 980 nm laser.