Near-infrared light-mediated DOX-UCNPs@mHTiO₂ nanocomposite for chemo/photodynamic therapy and imaging

Recently, incorporating multiple components into one nanoplatform for anticancer theranostics has attracted most attention. Herein, a rattle-structured nanocomposite by using UCNPs (NaYF₄:Yb,Tm@NaYF₄) as core coated with hollow mesoporous TiO₂ (UCNPs@mHTiO₂) was constructed as the nanocarrier. First, UCNPs@SiO₂@TiO₂ was prepared, by a selective etching method to remove SiO₂ shell, to make sure the hollow mesoporous structure and high surface area (347m²g^-1) of UCNPs@mHTiO₂. Under near-infrared (NIR) light irradiation, the UV emission can excite TiO₂ to produce ROS and to realize photodynamic therapy (PDT). In addition, the hollow structure offers space to store antitumor drug molecules (doxorubicin, DOX) and this nanocomposite also exhibits the improved DOX release in mildly acidic environment, which could greatly promote chemotherapy efficiency. Moreover, the luminescence resonance energy transfer (LRET) from UCNPs to DOX, owing to the effective distance restricted by the cavity, can be used to monitor the intercellular drug release kinetics. HeLa cells were used as the model cancer cells and the detailed cell experiments show the enhanced cytotoxicity, ascribing to the synergistic effect of chemotherapy and PDT. Therefore, the novel multifunctional nanocomposite, combining with chemotherapy, PDT, and imaging, should be a potential candidate in anticancer field.