Inhibition of Pro-Survival Autophagy Induced by Rare-Earth Nanocomposites for Promoting Photothermal Therapy of Visualized Tumors

Manipulation of autophagic processes has emerged as a promising strategy for synergizing nanoagent-mediated photothermal therapy (PTT). Most of the current studies focus on improving PTT efficacy by inhibiting pro-survival autophagy induced by the heat generated from the photothermal process. However, autophagy induced by the nanoagents is usually ignored, which may weaken the effect of autophagy-mediated efficacy improvement in PTT if induced autophagy is pro-death. Therefore, this work aims at developing a nanoagent that is able to induce heat-synergetic pro-survival autophagy to optimize the efficacy of PTT. An approach is developed to coat carbon layer, polyethylenimine (PEI), and folic acid (FA) on NaYF4:Er,Yb,Nd@NaNdF4 (DCNPs@C@PEI@FA, DCPF) nanoparticles successively, giving access to the nanoagent to induce pro-survival autophagy. The synthetic imaging-guided photothermal nanoagent displays outstanding targeting ability and biocompatibility based on the surface modification of PEI and FA. By using an autophagy inhibitor chloroquine, a conspicuously synergistic effect on DCPF-mediated PTT in vitro and in vivo tumor models (HeLa) is achieved. A promising strategy is presented here to enhance the efficacy of imaging-guided PTT by modulating the autophagy induced by the nanoagent.