Rare-Earth Metal Cations Incorporated Silica Hybrid Nanoparticles Templated by Cylindrical Polymer Brushes

A novel template-directed approach based on core–shell cylindrical polymer brushes (CPBs) has been developed to prepare rare-earth metal cations (Ln3+) incorporated silica hybrid nanoparticles (NPs) with predictable dimensions. Tight chelation of Ln3+ ions in the core of the CPB template and a cross-linked silica layer deposited on the shell provide a very stable encapsulation of Ln3+ ions within the hybrid NPs and thus a high biocompatibility. As expected, the silica hybrid NPs obtain unique and diverse properties from the incorporated Ln3+ ions. That is, the hybrid NPs with Tb3+ or Eu3+ incorporation exhibit characteristic photoluminescence in visible light range, while the Gd3+- and Tb3+-containing hybrid NPs show paramagnetic behavior. Especially, the Gd3+-containing silica hybrid NPs show a remarkable longitudinal relaxation time (T1) shortening effect as well as minimal cytotoxicity, suggesting the application potential of these NPs as effective magnetic resonance imaging (MRI) contrast agents. This novel template-directed approach succeeds in combining different functional centers via loading in situ mixed Ln3+ ions (e.g. Tb3+ and Gd3+) into individual CPBs resulting in multicomponent hybrid NPs, which possess both visible photoluminescence and T1 contrast enhancement and can thus be applied as multimodal bioimaging probes.