Polydopamine-coated NaGdF 4 :Dy for T 1 / T 2 -weighted MRI/CT multimodal imaging-guided photothermal therapy

The development of biocompatible theranostic agents with imaging and therapeutic functions is urgently desired for biomedicine and nanoscience. Herein, a novel polydopamine (PDA) coated lanthanide-based nanocomposite NaGdF 4 :Dy@PDA-PEG-FA (NaGdF 4 :Dy@PPF) has been successfully constructed for early diagnosis and treatment of tumors. MTT assay, histological analysis and the body weight changes of mice unambiguously revealed that this agent had relatively low cytotoxicity and negligible tissue damage. Due to the strong NIR absorption of PDA, this nanocomposite could be triggered effectively by 808 nm laser irradiation to produce an excellent photothermal conversion efficiency of 32.3%. Furthermore, NaGdF 4 :Dy@PPF displayed high longitudinal ( r 1 = 1.27 mM −1 s −1 ) and transverse ( r 2 = 126.0 mM −1 s −1 ) relaxivities, and a strong X-ray attenuation characteristic (43.56 HU L g −1 ). And T 1 / T 2 -weighted MRI and CT imaging in vivo confirmed that this nanocomposite could induce a significant contrast-enhancement effect on tumor sites at 24 h post injection. In addition, NaGdF 4 :Dy@PPF showed outstanding photothermal cytotoxicity against 4T1 cells and efficient inhibition of tumor growth under 808 nm irradiation. All these results demonstrated that this multifunctional nanoplatform had potential application as a novel multimodal imaging-guided PTT agent for early diagnosis and therapy of tumors.