Multifunctional hyaluronic acid ligand-assisted construction of CD44- and mitochondria-targeted self-assembled upconversion nanoparticles for enhanced photodynamic therapy†

Upconversion nanoparticles (UCNPs) have been used as a potential nanocarrier for photosensitizers (PSs), which have demonstrated a great deal of promise in achieving an effective photodynamic therapy (PDT) for deep-seated tumors. However, overcoming biological barriers to achieve mitochondria-targeted PDT remains a major challenge. Herein, CD44- and mitochondria-targeted photodynamic nanosystems were fabricated through the self-assembly of hyaluronic acid-conjugated-methoxy poly(ethylene glycol)-diethylenetriamine-grafted-(chlorin e6-dihydrolipoic acid-(3-carboxypropyl)triphenylphosphine bromide) polymeric ligands (HA-c-mPEG-Deta-g-(Ce6-DHLA-TPP)) and NaErF₄:Tm@NaYF₄ core–shell UCNPs (termed CMPNs). The CMPNs presented ideal physiological stability, a good drug loading capacity and an improved capacity for the generation of singlet oxygen (¹O₂) based on the FRET mechanism. Significantly, confocal images revealed that CMPNs not only facilitated cellular uptake through CD44-receptor-targeted endocytosis, subsequently enabling rapid evasion from endo-lysosomal sequestration, but also specifically targeted mitochondria, ultimately inducing a profound disruption of mitochondrial membrane potential, which triggered apoptosis upon laser irradiation, thereby significantly enhancing the therapeutic effect. Furthermore, in vitro antitumor experiments further confirmed the substantial enhancement in cancer cell killing efficiency achieved by treating with CMPNs upon near-infrared (NIR) laser irradiation. This innovative approach holds promise for the development of NIR-laser-activated photodynamic nanoagents specifically designed for mitochondria-targeted PDT, thus addressing the limitations of the current PDT treatments.