Construction of a targeted photodynamic nanotheranostic agent using upconversion nanoparticles coated with an ultrathin silica layer.

Two-activator codoped UCNPs served as energy donors and photosensitizers entrapped in an ultrathin silica layer served as energy acceptors to establish LRET-based photodynamic therapy with the advantages of shortened donor-to-acceptor distance and enhanced LRET efficiency. The exterior PEG-FA ligand further enhanced the biocompatibility and targetability to cancer cells and the tumor section.