Facile preparation of Eu3+ and F− co-doped luminescent hydroxyapatite polymer composites via the photo-RAFT polymerization

The luminescent hydroxyapatite nanorods co-doped with Eu 3+ and F − (named as FAp:Eu 3+ ) were synthesized through liquid-solid-solution strategy to control their size and morphology as well as improve their fluorescence. However, these luminescent FAp:Eu 3+ nanorods are hydrophobic nature and cannot be directly used for biomedical applications. In this work, we developed a novel strategy for surface modification of FAp:Eu 3+ nanorods with the combination of the surface ligand exchange reaction and photo-initiated reversible addition-fragmentation chain transfer (photo-RAFT) polymerization using the biocompatible and hydrophilic poly(ethylene glycol) methacrylate (PEGMA) as the monomer. We demonstrated that the photo-RAFT polymerization is a facile and efficient route to fabricate hydrophilic FAp:Eu 3+ -polyPEGMA composites based on a series of characterization techniques. The FAp:Eu 3+ -polyPEGMA composites still well maintained the morphology and luminescent properties. Furthermore, the resultant FAp:Eu 3+ -polyPEGMA composites showed low cytotoxicity and desirable cell uptake behavior. These features suggested that the FAp:Eu 3+ -polyPEGMA composites are of great potential for biological imaging applications. More importantly, the photo-RAFT polymerization should be promising for preparation of many other luminescent nanocomposites owing to their advantages of photo-RAFT polymerization such as low polymerization temperature, high efficiency, absence of metal catalysts and good monomer applicability. It is therefore, the photo-RAFT could be extended for fabrication of many other multifunctional fluorescent composites for different biomedical applications.