808 nm Light-triggered and hyaluronic acid-targeted dual-photosensitizers nanoplatform by fully utilizing Nd³⁺-sensitized upconversion emission with enhanced anti-tumor efficacy

The current near-infrared (NIR) light-induced photodynamic therapy (PDT) can enhance the tissue penetration depth to trigger photosensitizers (PSs) far from the surface. NIR-mediated PDT is still challenged by overheating effect on normal tissues, limited tumor selectivity and low reactive oxygen species (ROS) yields. Here we construct a dual-agent photosensitizing nanoplatform by combining UV-blue upconversion emitting NaYF₄:Yb/Tm@NaYF₄:Yb@NaNdF₄:Yb@NaYF₄ (labeled as UCNPs) multi-shell nanocrystals with titanium dioxide (TiO₂, UV-light-excited PS) and hypocrellin A (HA, blue-light-excited PS), which can induce cancer cell apoptosis by 808 nm light-triggered and hyaluronic acid (Hyal)-targeted PDT. In this construction strategy, the crystallized TiO₂ shells on the surface of UCNPs can play dual roles as UV-light excited PS and conjugation site for Hyal, and then Hyal is served as targeting-ligand as well as the carrier of HA simultaneously. The step-by-step reactive mode of loading PSs and modifying targeting-ligands is a controllable and ordered design based on the use of one intermediate product as the reaction site for the next component. The Nd³⁺-sensitized UCNPs with quenching reduction layer can efficiently convert 808 nm NIR light to UV-blue emission for simultaneous activation of two PSs with enhanced intracellular ROS generation. Through the in vitro and in vivo experiment results, the dual-photosensitizers nanoplatform presents enhanced anti-tumor efficacy by effective targeting cellular uptake and taking full advantage of upconversion emission, which may make a major step toward next generation of NIR-mediated PDT.