Programmed death-ligand 1 protein (PD-L1) is often expressed in various malignant tumors; thus, it is an appropriate marker for targeted cancer therapies. Photodynamic therapy (PDT) uses light and photosensitizers to create singlet oxygen to kill cells. An important approach to PDT is the use of upconversion nanoparticles (UCNPs) to convert near-infrared (NIR) light, which penetrates tissues well, into visible light, allowing PDT to be effective at greater tissue depths. In this work, high-temperature pyrolysis was used to prepare both the core and shell of lanthanide-doped UCNPs with lithium yttrium tetrafluoride (LiYF4) to enhance the green luminescence. The photosensitizer Merocyanine 540 (MC540) was grafted onto the magnetic nanoparticles, and then one peptide sequence from PD-L1 was used as the template and imprinted onto poly(ethylene-co-vinyl alcohol) particles formed by precipitation in a non-solvent. UCNPs in the non-solvent bath were thus entrapped in the imprinted particles to generate composite nanoparticles for the targeting and photodynamic therapy of PD-L1 in tumor cells. Finally, the in vitro cytotoxicity of the nanoparticles in HepG2 human liver cancer cells was evaluated with the continuous administration of MC540/MNPs@MIPs/UCNPs under irradiation by an NIR laser. To understand the delivery of the UCNP-embedded molecularly imprinted polymers, the intrinsic and extrinsic pathways were also investigated.
Embedded Upconversion Nanoparticles in Magnetic Molecularly Imprinted Polymers for Photodynamic Therapy of Hepatocellular Carcinoma
