Multifunctional UCNPs@PDA-ICG nanocomposites for upconversion imaging and combined photothermal/photodynamic therapy with enhanced antitumor efficacy.

Integrated theranostic nanosystems that combine therapeutic methods with suitable medical imaging modality are highly needed in the improvement of cancer theranostic approaches. Herein, polydopamine (PDA)-shelled NaYF:Yb,Er@NaYF:Yb nanoparticles (UCNPs) capable of loading indocyanine green (ICG) molecules via electrostatic adsorption, hydrophobic interaction and π-π stacking were successfully designed and synthesized (UCNPs@PDA-ICG, denoted as UPI) for upconversion imaging and combined photothermal/photodynamic therapy (PTT/PDT) with enhanced antitumor efficacy. We have found that ICG in this novel anticancer nanoplatform can be triggered impressively by 808-nm irradiation to produce both a photothermal effect and cytotoxic reactive oxygen species (ROS), thus achieving a good PTT/PDT synergistic effect. Notably, compared with free ICG molecules, UPI nanocomposites show much higher photostability and thermal stability. Both in vitro and in vivo experiments show that the as-obtained UPI can ablate cancer cells effectively with 808-nm irradiation, revealing their great potential as a NIR-mediated dual-modal therapeutic platform. Meanwhile, the core of UCNPs can be used for UCL imaging. All these results demonstrate great potentiality of UPI as a novel type of theranostic agent for the treatment of tumors.