Switchable up-conversion luminescence bioimaging and targeted photothermal ablation in one core–shell-structured nanohybrid by alternating near-infrared light

In photothermal therapy (PTT), simultaneous achievement of imaging and hyperthermia mediated by a single laser inevitably risks damaging normal tissues before treatment. Herein, a core-shell-structured GdOF:Yb/Er@(GNRs@BSA) nanohybrid was designed and fabricated by conjugating gold nanorods (GNRs) on the surfaces of GdOF:Yb/Er nanoparticles by a facile procedure. By alternating near-infrared (NIR) light appropriately, high photothermal efficiency for PTT and good up-conversion luminescence (UCL) imaging can be achieved in this structure, which can substantially solve the heat-induced risk during the theranostic process. Furthermore, good biocompatibility and phagocytosis can be realized by modifying bovine serum albumin (BSA) on the surface of the GNRs, and the conjugation of folic acid (FA) endows this nanohybrid with targeting function. It is noted that the size of the GNRs prepared by the one-pot method is much smaller than that by the seed-mediated method, which is not only conducive to uniform heat distribution during intratumoral therapy, but also contributes to the nanohybrid metabolic decomposition and fluorescence tracing after treatment. Moreover, this product can also be utilized as a good magnetic resonance imaging (MRI) and computed tomography (CT) contrast agent, which can provide versatile imaging properties in the field of cancer clinical treatment.