Two-Photon Luminescent Bone Imaging Using Europium Nanoagents

Abstract

Summary An accumulation of fatigue-induced microdamage can often result in an overall thinning and weakening of the bone's structure through a reduction in its mass, which increases its fragility and makes an individual more susceptible to fractures. Consequently, it is vitally important to detect and quantify microdamage early in order to diagnose skeletal diseases and combat their progression. Herein, we present the synthesis and study of europium [Eu(III)]-emitting surface-modified gold nanoparticles as contrast agents for imaging microdamaged bone structure at low concentrations. These nanostructures can be utilized to generate three-dimensional maps (z stacking) of microcracks formed within bone. Using two-photon excitation fluorescence microscopy, we were able to visualize and understand the manner in which these nanoagents bind to damaged bone, as well as demonstrate their selectivity toward exposed Ca(II) within microcracks. Such systems are therefore ideal for biological application as targeted contrast agents for both optical imaging and MRI.