Gold Cube-in-Cube Based Oxygen Nanogenerator: A Theranostic Nanoplatform for Modulating Tumor Microenvironment for Precise Chemo-Phototherapy and Multimodal Imaging.

Engineering a versatile oncotherapy nanoplatform integrating both diagnostic and therapeutic functions has always been an intractable challenge in targeted cancer treatment. Herein, to actualize the theme of precise medicine, a nanoplatform is developed by anchoring Mn-Cdots to doxorubicin (DOX)-loaded mesoporous silica-coated gold cube-in-cubes core/shell nanocomposites and further conjugating them to a Arg-Gly-Asp (RGD) peptide (denoted as RGD-CCmMC/DOX) to achieve active-targeting effect. Under a 635 nm irradiation, the nanoplatform acts as oxygen nanogenerator that produces O2 in situ and amplifies the content of singlet oxygen (1O2) in the hypoxic tumor microenvironment (TME), which has been demonstrated to attenuate tumor hypoxia and synchronously enhance photodynamic efficacy. Moreover, the gold cube-in-cube core in this work has proven as a photothermal agent for hyperthermia, which exhibits a favorable photothermal effect with a 65.6% calculated photothermal conversion efficiency under 808 nm irradiation. In addition, the nanoplatform achieves heat/pH-sensitive drug realease with precise control to specific-tumor sites, executing combined chemo-phototherapy functions. Besides, it functions as a multimodal bioimaging agent of photothermal, fluorescence and magnetic resonance imaging for accurate diagnosis and guidance of therapy. As validated by in vivo and vitro assays, the TME-responsive nanoplatform is highly biocompatible and effectively obliterates 4T1 tumor xenograft on nude mice after triple-synergetic treatment. This work presents a rational design of versatile nanoplatforms which modulate the TME to enable high therapeutic performance and multiplexed imaging, which provides an innovative paradigm for targeted tumor therapy.