The photoluminescence, drug delivery and imaging properties of multifunctional Eu3+/Gd3+ dual-doped hydroxyapatite nanorods

The design and synthesis of multifunctional systems with high biocompatibility are very significant for the future of clinical applications. Herein, we report a microwave-assisted rapid synthesis of multifunctional Eu3+/Gd3+ dual-doped hydroxyapatite (HAp) nanorods, and the photoluminescence (PL), drug delivery and in vivo imaging of as-prepared Eu3+/Gd3+ doped HAp nanorods. The photoluminescent and magnetic multifunctions of HAp nanorods are realized by the dual-doping with Eu3+ and Gd3+. The PL intensity of doped HAp nanorods can be adjusted by varying Eu3+ and Gd3+ concentrations. The magnetization of doped HAp nanorods increases with the concentration of doped Gd3+. The as-prepared Eu3+/Gd3+-doped HAp nanorods exhibit inappreciable toxicity to the cells in vitro. More importantly, the Eu3+/Gd3+-doped HAp nanorods show a high drug adsorption capacity and sustained drug release using ibuprofen as a model drug, and the drug release is governed by a diffusion process. Furthermore, the noninvasive visualization of nude mice with subcutaneous injection indicates that the Eu3+/Gd3+-doped HAp nanorods with the photoluminescent function are suitable for in vivo imaging. In vitro and in vivo imaging tests indicate that Eu3+/Gd3+-doped HAp nanorods have a potential in applications such as a multiple-model imaging agent for magnetic resonance (MR) imaging, photoluminescence imaging and computed tomography (CT) imaging. The Eu3+/Gd3+ dual-doped HAp nanorods are promising for applications in the biomedical fields such as multifunctional drug delivery systems with imaging guidance.