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Preparation of multifunctional upconversion nanoconstruct for in vitro and in vivo imaging and photodynamic therapy induced by near-infrared light

Upconversion nanoparticles (UCNPs) have attracted much attention as novel contrast agents for low-background biomedical imaging and potential photosensitizer carriers for photodynamic therapy (PDT) in deep tissues. In this work, firstly we synthesized NaYF4:Yb3+,Tm3+@NaYF4:Yb3+,Er3+ core-shell structured UCNPs with multiple emission peaks (e.g. 480, 539, 654 and 800 nm) by a seeded growth approach. By coating folate-modified amphiphilic chitosan (FASOC) on UCNPs, the as-prepared UCNPs were favorably endowed with good water solubility and the enhanced tumor-selectivity to cancer cells that overexpressed folate receptor. Then, water-insoluble photosensitizer zinc(II) phthalocyanine (ZnPc) was loaded into the FASOC-UCNPs via hydrophobic interactions for potential near-infrared light induced photodynamic therapy (PDT). Our results indicate that the multifunctional FASOC-UCNP-ZnPc nanoconstruct has efficient NIR-to-NIR upconversion luminescence and PDT abilities, which could be potentially employed as a theranostic platform for cancer treatment.