Multifunctional Eu3+/Gd3+ dual-doped calcium phosphate vesicle-like nanospheres for sustained drug release and imaging

A facile room-temperature solution method is reported for the preparation of multifunctional Eu3+ and Gd3+ dual-doped calcium phosphate (CaP) (Eu3+/Gd3+−CaP) vesicle-like nanospheres in the presence of an amphiphilic block copolymer polylactide–block–monomethoxy(polyethyleneglycol) (PLA−mPEG). The photoluminescent (PL) and magnetic multifunctions of CaP vesicle-like nanospheres are realized by dual-doping with Eu3+/Gd3+ ions. Under the excitation at 393 nm, Eu3+/Gd3+−CaP vesicle-like nanospheres exhibit a strong near-infrared (NIR) emission at 700 nm, and the PL intensity can be adjusted by varying Eu3+ and Gd3+ concentrations. Furthermore, Eu3+/Gd3+−CaP vesicle-like nanospheres can be used as the drug nanocarrier and have a high drug loading capacity and ultralong sustained drug release using ibuprofen as a model drug. The drug release from the drug delivery system of Eu3+/Gd3+−CaP vesicle-like nanospheres can sustain for a very long period of time (more than 80 days). The as-prepared Eu3+/Gd3+−CaP vesicle-like nanospheres exhibit essentially inappreciable toxicity to the cells in vitro. The noninvasive visualization of nude mice with subcutaneous injection indicates that the Eu3+/Gd3+−CaP vesicle-like nanospheres are suitable for in vivo bio-imaging. In vivo imaging tests using the subcutaneous injection model of nude mice indicate that Eu3+/Gd3+−CaP vesicle-like nanospheres can be used as an imaging agent for the NIR luminescence imaging. Thus, the Eu3+/Gd3+−CaP vesicle-like nanospheres are promising for applications in the biomedical fields such as multifunctional drug delivery systems and tissue engineering scaffolds with bio-imaging guidance.