Phosphorescent Coordination Polymer Nanoparticles as a Three-in-One Platform for Optical Imaging, T1-Weighted Magnetic Resonance Imaging, and Photodynamic Therapy

Abstract

Water-soluble coordination polymer nanoparticles (Ir–Gd CPPs) were conveniently synthesized in high yields in the presence of polyvinylpyrrolidone (PVP), adopting magnetic Gd(III) ions, and phosphorescent iridium complexes with carboxyl groups as building blocks. The Ir–Gd CPPs showed good stability in simulated biological media and low cytotoxicity toward a model line of HeLa cancer cells. The Ir–Gd CPPs exhibited absorption in the visible region, red phosphorescence centered at 560 nm, and higher longitudinal relaxivity (r1) of ∼29.5 mM–1 s–1 in a 3 T MRI system. Furthermore, the effective uptake of Ir–Gd CPPs by HeLa cells was confirmed by confocal laser scanning microscopy and flow cytometry, suggesting they may be useful as an optical probe for living cells. The generation of 1O2 upon irradiation with a visible light prompted an investigation into the possibility of using Ir–Gd CPPs in photodynamic therapy. After incubation with 200 μg mL–1 of Ir–Gd CPPs for 6 h, the viability of HeLa cells was only ∼16.6% after irradiation with a visible light (λ > 400 nm, 300 mW cm–2).