Photodynamic Therapy and Simultaneous Fluorescence Imaging

In vivo biological application of upconversion nanoparticles (UCNPs) prefers excitation of 700-850 nm, instead of 980 nm, due to the absorption of water. Recently approach in constructing robust Nd doped UCNPs subject to 808 nm excitation relies on a thick Nd sensitized shell. However, for the very 10 important and popular Förster resonance energy transfer (FRET)-based applications, such as photodynamic therapy (PDT) or switchable biosensor, this structure has its restriction resulting in a poor energy transfer. We have in this work designed the NaYF4:Yb/Ho@NaYF4:Nd@NaYF4 core-shell-shell nanostructure. It is proved that this optimal structure balances the robustness of the upconversion emission and the FRET efficiency for FRET-based bio-application. A proof of the concept was 15 demonstrated for photodynamic therapy and simultaneous fluorescence imaging of Hela cell triggered by 808 nm light, where low heating and high PDT efficacy were reached.