Aza-BODIPY Probe-Decorated Mesoporous Black TiO₂ Nanoplatform for the Highly Efficient Synergistic Phototherapy

As an important noninvasive tumor treatment method, phototherapy has drawn extensive research interest. However, the requirements of separate excitation wavelengths, high degree of electron-hole recombination, and low reactive oxygen species (ROS) production capability are still the major barriers. This work reports the construction of a novel nanoplatform: design and synthesis of an aza-BODIPY (AB) probe-decorated mesoporous black titanium dioxide (TiO₂) (MT) nanoparticles (NPs) for enhanced photodynamic therapy and photothermal therapy under single-wavelength near-infrared (NIR) laser irradiation for the first time. AB probe-decorated MT NPs (abbreviated as MTAB) were synthesized through the Al reduction of mesoporous anatase TiO₂ NPs and subsequent adsorption of the AB probe. The mesoporous structure of MT ensured AB loading capacity and avoided the complicated modification and synthesis processes. Heterogeneous MTAB, which possessed staggered energy levels, were assessed for their capability for effective separation of photogenerated electrons and holes for the first time. Upon NIR laser light irradiation, MTAB exhibited sufficient ROS generation, resulting in distinct tumor cell killing and tumor tissue elimination. This unique heterogeneous nanoplatform with staggered energy levels provides a new strategy to enhance ROS generation and improve the therapeutic efficacy.