Surface modification of fluorescent Tb3+-doped layered double hydroxides with hyperbranched polymers through host-guest interaction.

The preparation of fluorescent inorganic-organic polymer composites for biomedical applications has become one of the most interest research focuses recently. In this work, we reported a novel method for the preparation of Tb3+-doped luminescent layered double hydroxides (LDHs) based composites by taken advantage of a one-pot supramolecular chemistry. The adamantane can be immobilized on the surface of Tb3+-doped LDHs to obtain LDH-Ad, which could be further utilized for modified by the ß-cyclodextrin (ß-CD) containing hyperbranched polyglycerols (ß-CD-HPG) through the host-guest interaction. Based on the characterization results, we demonstrated that the hyperbranched polyglycerol could be facilely introduced on these fluorescent Tb3+-doped LDHs through the method described in this work. The obtained Tb3+-doped LDHs based polymer composites (LDHs-ß-CD-HPG) display improved water dispersibility and still maintain their fluorescence. The results based on various biological assays suggest that LDHs-ß-CD-HPG polymer composites are of low cytotoxicity and their cell uptake behavior can be effectively traced using confocal laser imaging. All of the above results demonstrated that the fluorescent Tb3+-doped LDHs based polymer composites could be effectively surface modified with hydrophilic hyperbranched polymers through a one-pot facile host-guest interaction and the resultant fluorescent composites are of excellent physicochemical properties and display great potential for biomedical applications. This novel surface modification method should also be important for fabrication of other multifunctional composites and therefore great advanced the development of biomedical applications of fluorescent LDHs based polymer composites and related materials.

Surface PEGylation and biological imaging of fluorescent Tb3+-doped layered double hydroxides through the photoinduced RAFT polymerization.

Tb3+-doped layered double hydroxides (LDHs) exhibit excellent optical characteristics, uniform size and uniform morphologies when synthesized through a hydrothermal method. However, due to their lack of functional groups and poor dispersibility, applications of these fluorescent Tb3+-doped LDHs have been largely impeded especially in the biomedical fields. In this work, a novel strategy was developed for the surface modification of these fluorescent Tb3+-doped LDHs using photoinduced surface-initiated reversible addition-fragmentation chain transfer (RAFT) polymerization with hydrophilic poly(ethylene glycol) methacrylate (PEGMA) as the monomer. The final products were obtained via the metal free surface-initiated RAFT polymerization with light irradiation. Successful preparation of these fluorescent LDHs polymer composites (LDH-PEG) was confirmed by a number of analytical technologies, such as transmission electron microscopy, Fourier transformed infrared spectroscopy, X-ray photoelectron spectroscopy and thermogravimetric analysis. In addition, laser scanning confocal microscope was employed to examine the cell uptake behavior of the LDH-PEG composites and evaluate their potential for biomedical applications. We demonstrated that the hydrophilic monomer PEGMA could be facilely grafted on the surface of Tb3+-doped LDHs through metal free photoinduced surface-initiated RAFT polymerization. The resultant LDH-PEG composites displayed high water dispersibility, strong fluorescence, low cytotoxicity and a desirable cell uptake performance. These features of the LDH-PEG composites indicated their great potential for biomedical applications. More importantly, photoinduced RAFT polymerization has the advantages of a conventional controlled living radical polymerization, which could overcome drawbacks such as toxicity, the fluorescence quenching effects of metal catalysts and the complex synthesis of chain transfer agents. Therefore, this method could be an alternative tool for the surface modification of materials and fabrication of multifunctional fluorescent nanomaterials based polymer composites.