Core-satellite metal-organic framework@upconversion nanoparticle superstructures via electrostatic self-assembly for efficient photodynamic theranostics

The nanoplatforms based on upconversion nanoparticles (UCNPs) have shown great promise in amplified photodynamic therapy (PDT) triggered by near-infrared (NIR) light. However, their practical in vivo applications are hindered by the overheating effect of 980 nm excitation and low utilization of upconversion luminescence (UCL) by photosensitizers. To solve these defects, core-satellite metal-organic framework@UCNP superstructures, composed of a single metal-organic framework (MOF) NP as the core and Nd³⁺-sensitized UCNPs as the satellites, are designed and synthesized via a facile electrostatic self-assembly strategy. The superstructures realize a high co-loading capacity of chlorin e6 (Ce6) and rose bengal (RB) benefitted from the highly porous nature of MOF NPs, showing a strong spectral overlap between maximum absorption of photosensitizers and emission of UCNPs. The in vitro and in vivo experiments demonstrate that the dual-photosensitizer superstructures have trimodal (magnetic resonance (MR)/UCL/fluorescence (FL)) imaging functions and excellent antitumor effectiveness of PDT at 808 nm NIR light excitation, avoiding the laser irradiation-induced overheating issue. This study provides new insights for the development of highly efficient PDT nanodrugs toward precision theranostics.