A metal–organic framework based nanocomposite with co-encapsulation of Pd@Au nanoparticles and doxorubicin for pH- and NIR-triggered synergistic chemo-photothermal treatment of cancer cells

Here, we report a novel metal-organic framework-based nanocomposite with encapsulated Pd@Au nanoparticles and doxorubicin (DOX) for pH- and NIR-triggered synergistic chemo-photothermal treatment of cancer cells. In this work, Pd nanoparticles, which have uniform size and dispersibility, were first synthesized and used as a template to direct the covering of Au nanosheets. The obtained Au coated Pd (Pd@Au) nanoparticles have excellent dispersibility and photothermal conversion ability, which makes them a good photothermal nanomaterial. Subsequently, an acid-degradable metal-organic framework of ZIF-8 was employed to synchronously encapsulate Pd@Au nanoparticles and DOX to get a metal-organic framework-based nanocomposite (DOX/Pd@Au@ZIF-8). Under acid conditions (e.g. pH ∼5.0 in a lysosome), the ZIF-8 framework of the DOX/Pd@Au@ZIF-8 nanocomposite could be degraded, resulting in the release of encapsulated DOX. Moreover, the present Pd@Au nanoparticles can effectively convert NIR laser light (780 nm, 2.1 W cm^-2) into heat, not only further promoting the release of DOX, but also realizing the synergistic chemo-photothermal treatment of cancer cells. The in vitro experiments showed that this nanocomposite system has an excellent synergistic treatment effect on SMMC-7721 cells, even at low concentrations (e.g. 20 μg mL^-1). With the properties of synergistic chemo-photothermal treatment, we hope that such a nanocomposite system of DOX/Pd@Au@ZIF-8 could open the door to designing a significant multifunctional system for diverse applications in cancer treatment.