Design of Hydroxyapatite-Based Multifunctional Nanoparticles for Cell Labelling and Cell Growth Inhibition

There has been an increasing demand for the development of cell-labeling nanomaterials that safely label and visualize a specific type of cells for diagnosis and inspection in vivo and in vitro. In order to design such cell-labeling nanomaterials, the properties of efficient visible light luminescence and effective interactions with cells have to be realized using a biocompatible nanomaterial. From this viewpoint, we summarize and overview the current situation on cell-labeling technologies. Among various functional nanomaterials, we focus on hydroxyapatite nanoparticles and their photofunctionalization based on the properly designed inorganic-organic hybrid structure such as hydroxyapatite/ organic europium (III) complex. Also, the immobilization technique of a specific binding molecule to the solid surface is introduced to demonstrate the selective uptake into cancer cells. Moreover, an example of the growth inhibitory drug molecules for cancer cells are described, focusing on the cytostatic inhibition of citric acid and the potential use of hydroxyapatite/citric acid hybrids. Finally, we mention our future perspectives on the theranostic nanoparticles with fluorescence and therapeutic properties that are achieved through the hydroxyapatite-organic hybrid interfacial interactions.