Multimodal Nanoparticle Bioengineering for X-Ray Fluorescence Imaging

Multimodal nanoparticles (NPs) are promising contrast agents for multiscale and complementary bioimaging. It is essential to study the interactions between the cellular environment and NPs in order to evaluate their functional and toxic properties. Here, we present a methodology for complementary imaging to evaluate the biocompatibility and biodistribution of dual-mode hybrid NPs <i>in vitro</i> and <i>in vivo</i>. These inorganic NPs are composed of an X-ray fluorescent (XRF) active element, complemented with dye-doped silica coating, conjugated carbon quantum dots, or decorated superparamagnetic iron oxide NPs. We investigated the advantages of whole-animal XRF imaging and local XRF computed tomography (XFCT), characterized by high specificity and sensitivity. The complementary properties enabled the multiscale visualization of the NPs<i> in vitro</i> and in tissues from excised organs via optical fluorescence microscopy and correlative imaging with <i>in vivo</i> magnetic resonance imaging (MRI). The optimization of the hybrid NP surface chemistry and colloidal stability led to biocompatible contrast agents for XRF molecular imaging.