Upconverting Nanoparticles with a Mesoporous TiO 2 Shell for Near‐Infrared‐Triggered Drug Delivery and Synergistic Targeted Cancer Therapy

Malignant tumors remain a major health burden throughout the world and effective therapeutic strategies are urgently needed. Herein, we report the synthesis of upconverting nanoparticles with a mesoporous TiO 2 (mTiO 2 ) shell for near‐infrared (NIR)‐triggered drug delivery and synergistic targeted cancer therapy. The NaGdF 4 :Yb,Tm could convert NIR light to UV light, which activated the mTiO 2 to produce reactive oxygen species for photodynamic therapy (PDT). Due to the large surface area and porous structure, the mTiO 2 shell endowed the nanoplatform with another functionality of anticancer drug loading for chemotherapy. The hyaluronic acid modified on the surface not only promised controlled drug release but also conferred targeted ability of the system toward cluster determinant 44 overexpressed cancer cells. More importantly, cytotoxicity experiments demonstrated that combined therapy mediated the highest rate of death of breast carcinoma cells compared with that of single chemotherapy or PDT.