Abstract: The development of upconversion nanoparticles (UCNs) for theranostics application is a new strategy toward the accurate diagnosis and efficient treatment of cancer. Here, magnetic and fluorescent lanthanide-doped gadolinium oxide (Gd₂O₃) UCNs with bright upconversion luminescence (UCL) and high longitudinal relaxivity (r ₁) are used for simultaneous magnetic resonance imaging (MRI)/UCL dual-modal imaging and photodynamic therapy (PDT). In vitro and in vivo MRI studies show that these products can serve as good MRI contrast agents. The bright upconversion luminescence of the products allows their use as fluorescence nanoprobes for live cells imaging. We also utilized the luminescence-emission capability of the UCNs for the activation of a photosensitizer to achieve significant PDT results. To the best of our knowledge, this study is the first use of lanthanide-doped Gd₂O₃ UCNs in a theranostics application. This investigation provides a useful platform for the development of Gd₂O₃-based UCNs for clinical diagnosis, treatment, and imaging-guided therapy of cancer.
Keywords: upconversion nanoparticles, upconversion luminescence imaging, MR imaging, photodynamic therapy, singlet oxygen