Multifunctional photosensitizer-conjugated core–shell Fe3O4@NaYF4:Yb/Er nanocomplexes and their applications in T2-weighted magnetic resonance/upconversion luminescence imaging and photodynamic therapy of cancer cells

Abstract

Due to non-invasive deep imaging and therapy, multifunctional agents of magnetic resonance (MR)/upconversion luminescence (UCL) imaging and photodynamic therapy (PDT) play an important role in clinical diagnosis and treatment of cancers, and also in the assessment of therapy effect. In this paper, tetra-sulfonic phthalocyanine aluminium (AlPcS₄) photosensitizers-conjugated Fe₃O₄@NaYF₄:Yb/Er (NPs-AlPcS₄) nanocomplexes were synthesized for the T₂-weighted MR/UCL imaging and PDT of cancer cells. The PEG-coated Fe₃O₄@NaYF₄:Yb/Er nanoparticles (NPs) with a core–shell structure showed strong T₂-weighted MR relaxivity (r₂ = 42.131 mM⁻¹ s⁻¹) and UCL emission in the visible region (the bands at about 654–674 nm, 545 nm and 524 nm), and were conjugated successfully with AlPcS₄ photosensitizer by electrostatic interaction. By direct observation of XFM and staining with Prussian blue, the element distribution and location of NPs in MCF-7 cells were characterized, respectively. Under irradiation from a 980 nm laser, the death ratio of MCF-7 cells incubated with NPs-AlPcS₄ nanocomplexes could be up to about 70%. The results indicated that the as-prepared NPs-AlPcS₄ nanocomplexes would be a potential candidate as multifunctional nanoprobes for the dual-modal T₂-weighted MR/UCL imaging and PDT of cancers in the future.