High-efficiency cancer treatment remains the main challenge at present. In this study, a mesoporous platinum nanoparticle- (mesoPt) based nanoplatform is exported for effective tumor treatment, integrating computed tomography (CT) imaging, photothermal conversion, and chemotherapeutic drug delivery capabilities. Mesoporous platinum nanoparticles are facilely synthesized by using Pluronic F127 as a structure-directing agent without seeds or organic reagents and have a spherical structure and uniform diameter of 94 nm. The surface of the mesoPt is modified with polyethylene glycol (PEG), and the prepared mesoPt-PEG shows excellent biocompatibility. Doxorubicin (Dox)-loaded PEG@Pt (PEG@Pt/Dox) is further prepared by electrostatic adsorption and the drug-loading capacity is as high as 25%. In vitro studies demonstrate that Dox can be controllably released from PEG@Pt/Dox in pH 5.5 phosphate buffered solution (PBS). Confocal imaging verifies that PEG@Pt/Dox can efficiently enter Dox-resistant breast cancer cells (MCF-7/ADR), deliver Dox into the cytoplasm when incubated for 1 h or 12 h, and release Dox into the nucleus when incubation is prolonged to 24 h. Cell transmission electron microscopy and flow cytometry also confirm that PEG@Pt/Dox could be internalized by cells. Upon irradiation by an 808 nm laser, the anticancer effect of PEG@Pt/Dox is significantly improved and kills approximately 84% of cancer cells when the concentration of Dox is 8 mu g/mL. The killing efficacy of MCF-7/ADR cells is significantly higher in the combination group than in the monochemotherapy group. Hence, multifunctional nanoplatform PEG@Pt/Dox presents an effective strategy to realize efficient combination of chemotherapy and photothermals for drug-resistant cancer. (C) 2020 Elsevier Inc. All rights reserved.