Titania-coated 2D gold nanoplates as nanoagents for synergistic photothermal/sonodynamic therapy in the second near-infrared window

Abstract

The development of efficient nanomedicines to improve anticancer therapeutic effects is highly attractive. In this work, we firstly report titania-coated Au nanoplate (Au NPL@TiO₂) heterostructures, which play dual roles as nanoagents for synergistic photothermal/sonodynamic therapy in the second near-infrared (NIR) window. On the one hand, because the controlled TiO₂ shells endow the Au NPL@TiO₂ nanostructures with a red shift to the NIR II region, the as-prepared Au NPL@TiO₂ nanostructures possess a high photothermal conversion efficiency of 42.05% when irradiated by a 1064 nm laser and are anticipated to be very promising candidates as photothermal agents. On the other hand, the Au nanoplates (Au NPLs), as electron traps, vastly improve the generation of reactive oxygen species (ROS) by the Au NPL@TiO₂ nanostructures in contrast with pure TiO₂ shell nanoparticles upon activation by ultrasound (US) via a sonodynamic process. Moreover, the toxicity and therapeutic effect of the Au NPL@TiO₂ nanostructures were relatively systemically evaluated in vitro. The Au NPL@TiO₂ nanostructures generate a large amount of intracellular ROS and exhibit laser power density-dependent toxicity, which eventually induces apoptosis of cancer cells. Furthermore, a synergistic therapeutic effect, with a cell viability of only 20.3% upon both photothermal and sonodynamic activation, was achieved at low concentrations of the Au NPL@TiO₂ nanostructures. Experiments on mice also demonstrate the superiority of the combination of PTT and SDT, with the total elimination of tumors. This work provides a way of applying two-dimensional (2D) gold nanoplate core/TiO₂ shell nanostructures as novel nanoagents for advanced multifunctional anticancer therapies in the second NIR window.