A Core–Shell-Satellite Structured Fe3O4@g-C3N4–UCNPs–PEG for T1/T2-Weighted Dual-Modal MRI-Guided Photodynamic Therapy

Reactive oxygen species (ROS) produced in the specific tumor site plays the key role in photodynamic therapy (PDT). Herein, a multifunctional nanoplatform is designed by absorbing ultrasmall upconversion nanoparticles (UCNPs) on mesoporous graphitic-phase carbon nitride (g-C₃N₄) coated superparamagnetic iron oxide nanospheres, then further modified with polyethylene glycol (PEG)molecules (abbreviated as Fe₃O₄@g-C₃N₄–UCNPs–PEG). The inert g-C₃N₄ layer between Fe₃O₄ core and outer UCNPs can substantially depress the quenching effect of Fe₃O₄ on the upconversion emission. Upon near-infrared (NIR) laser irradiation, the UCNPs convert the energy to the photosensitizer (g-C₃N₄ layer) through fluorescence resonance energy transfer process, thus producing a vast amount of ROS. In vitro experiment exhibits an obvious NIR-triggered cell inhibition due to the cellular uptake of nanoparticles and the effective PDT efficacy. Notably, this platform is responsive to magnetic field, which enables targeted delivery under the guidance of an external magnetic field and supervises the therapeutic effect by T₁/T₂-weighted dual-modal magnetic resonance imaging. Moreover, in vivo therapeutic effect reveals that the magnetism guided accumulation of Fe₃O₄@g-C₃N₄–UCNPs–PEG can almost trigger a complete tumor inhibition without any perceived side effects. The experiments emphasize that the excellent prospect of Fe₃O₄@g-C₃N₄–UCNPs–PEG as a magnetic targeted platform for PDT application.

A multifunctional nanoplatform demonstrates NIR-irradiated, magnetic targeted, and T₁/T₂-weighted dual-modal magnetic resonance imaging guided photodynamic anticancer therapy. The platform is constructed by coating mesoporous g-C₃N₄ on Fe₃O₄ nanoparticles, following by attaching ultrasmall upconversion nanoparticles (UCNPs) and PEG molecules (denoted as Fe₃O₄@g-C₃N₄–UCNPs–PEG).

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