When a Semiconductor Utilized as an NIR Laser-Responsive Photodynamic/Photothermal Theranostic Agent Integrates with Upconversion Nanoparticles

Photoactive theranostics including photodynamic therapy (PDT) hace aroused an intensive interest that combines medical diagnostics with treatment under a single irradiation laser. However, the conventional organic PDT agents usually suffer from aggregation caused by the quenching effect. In this research, we designed a core–shell–shell (CSS) UCNPs with NaGdF4 as the host, and the UCNPs could emit higher blue/green light by the energy transfer processes among Nd/Yb/Tm/Gd/Tb under 808 nm laser. When the CSS UCNPs were combined with the MnO2 semiconductor as the energy acceptor, CSS@Mn could be utilized as an effective PDT agent under a NIR laser. The temperature also increased more than 12.2 °C under the 808 nm laser, indicating the potential of synergistic photothermal therapy (PTT) and PDT. Interestingly, cells with small amounts of H2O2 could be responsive to the CSS@Mn platform. The antitumor effect was proved by the in vitro and in vivo experiments. Also, the biocompatibility, biodistribution, and excretion pathway were detected and revealed by the H&E stained pathological section and photoacoustic (PA) images. That means this platform could be potentially used as antitumor PDT/PTT agents.