Epitaxial growth of heterostructured nanoparticles for biomedical applications

With the development of nanotechnology, inorganic nanoparticles have attracted tremendous interest as agents for biomedical diagnosis and therapy due to their unique properties. In the past decade, numerous inorganic nanoparticles, such as quantum dots (QDs) (Reiss et al. 2009; Zhu et al. 2013), upconversion nanoparticles (UCNPs) (Chen et al. 2013; Chen et al. 2015; Wang et al. 2013a; Zhou et al. 2012), superparamagnetic iron oxide nanoparticles (SPIONs) (Gobbo et al. 2015; Santhosh and Ulrih 2013; Singh and Sahoo 2014) and gold nanoparticles (Cai et al. 2008; Dreaden et al. 2012), have been employed for different biomedical applications. Among these inorganic nanomaterials, heterostructured nanoparticles which contain two or more components have been increasingly explored and are expected to play increasingly important roles in preclinical/clinical research in the future (He and Lin 2015; Sailor and Park 2012). Different hybrid nanostructures including core/shell, heterodimer and dumbbell structures have been designed and applied for biomedical purposes. As compared to conventional inorganic nanoparticles, the incorporation of second (or multiple) components offers heterostructured nanoparticles enhanced properties and enriched 55functionalities. For example, the growth of a shell or multiple shells onto QDs have successfully enhanced their fluorescence quantum yield and reduced their cytotoxicity (Ghosh Chaudhuri and Paria 2012). Similarly, the core/shell structure has also been widely studied to enhance emission efficiency and tune optical properties of UCNPs (Chen et al. 2015). In addition, dumbbell structured Au-Fe3O4 nanohybrids have been designed for simultaneous optical imaging and magnetic resonance imaging (MRI) (Yu et al. 2005).