Near-Infrared Upconversion Mesoporous Tin Dioxide Theranostic Nanocapsules for Synergetic Cancer Chemophototherapy

Smart nanotheranostic systems (SNSs) have attracted extensive attention in antitumor therapy. Nevertheless, constructing SNSs with disease diagnosis ability, improved drug delivery efficiency, inherent imaging performance, and high treatment efficiency remains a scientific challenge. Herein, ultrasmall tin dioxide (SnO2) was assembled with upconversion nanoparticles (UCNPs) to form mesoporous nanocapsules by an in situ hydrothermal deposition method, followed by loading with doxorubicin (DOX) and modification with bovine serum albumin (BSA). pH/near-infrared dual-responsive nanotheranostics was constructed for computed tomography (CT) and magnetic resonance (MR) imaging-induced collaborative cancer treatment. The mesoporous channel of SnO2 was utilized as a reservoir to encapsulate DOX, an antineoplastic drug, for chemotherapy and as a semiconductor photosensitizer for photodynamic therapy (PDT). Furthermore, the DOX-loaded UCNPs@SnO2-BSA nanocapsules combined PDT, Nd3+-doped UCNP-triggered hyperthermia effect, and DOX-triggered chemotherapy simultaneously and demonstrated prominently enhanced treatment efficiency compared to the monotherapy model. Moreover, tin, as one of the trace elements in the human body, has a similar X-ray attenuation coefficient to iodine and therefore can act as a contrast agent for CT imaging to monitor the treatment process. Such an orchestrated synergistic anticancer treatment exhibited apparent inhibition of tumor growth in tumor-bearing mice with negligible side effects. Our study demonstrates nanocapsules with excellent biocompatibility and great potential for cancer treatment.