miR‐21‐Trigged Precise Photodynamic Therapy Through a “Locking‐Unlocking‐Boosting” ROS Production Strategy

Abstract Photodynamic therapy (PDT) stands out as a highly promising modality for tumor treatment, yet previous works have primarily centered around either boosting the production of reactive oxygen species (ROS) in tumor tissues or restricting it in normal tissues. The current challenge lies in the urgent need to achieve precise modulation of ROS production by simultaneously controlling both aspects. To achieve this goal, a precise PDT platform through a “locking‐unlocking‐boosting” ROS production strategy is presented, in which the generation of ROS is modulated by bidirectionally regulating the upconversion luminescence (UCL) of lanthanide‐doped nanoparticles (LnNPs), thus ROS production is “locked” in normal tissues but “boosted” in tumor tissues. In detail, by introducing an energy acceptor BHQ3, the UCL is initially quenched to prevent Chlorin e6 (Ce6) from generating ROS. However, under the tumor microenvironment with overexpressed miR‐21, LnNPs are sequestered from BHQ3 to “unlock” ROS generation and then assembled with QDs@B2, which functions as an antenna to sensitize LnNPs luminescence, to further “boost” ROS generation. With the assistance of spherical nucleic acids, this therapeutic agent effectively traverses the blood‐brain barrier (BBB), enabling efficient PDT for glioblastoma.