Abstract
Nanoparticles (NPs) have been used as contrast agents for several bioimaging modalities. X-ray fluorescence (XRF) tomography can provide sensitive and quantitative 3D detection of NPs. With spectrally matched NPs as contrast agents, we demonstrated earlier in a laboratory system that XRF tomography could achieve high-spatial-resolution tumor imaging in mice. Here, we present the synthesis, characterization, and evaluation of a library of NPs containing Y, Zr, Nb, Rh, and Ru that have spectrally matched K-shell absorption for the laboratory scale X-ray source. The K-shell emissions of these NPs are spectrally well separated from the X-ray probe and the Compton background, making them suitable for the lab-scale XRF tomography system. Their potential as XRF contrast agents is demonstrated successfully in a small-animal equivalent phantom, confirming the simulation results. The diversity in the NP composition provides a flexible platform for a better design and biological optimization of XRF tomography nanoprobes.
Highlights
Nanostructured materials have reached a central role in nanomedicine, in the search of new diagnostic and therapeutic agents
We recently reported on a laboratory scale X-ray fluorescence (XRF) tomography system [26] with spectrally matched molybdenum (Mo)-based NPs as the contrast agent, enabling high-spatial-resolution tumor imaging in mice. e X-ray source has a characteristic 24 keV line emission well matched by the K-absorption edge of Mo (20.0 keV, Kα XRF at 17.4 keV), showing promising potential for in vivo small-animal imaging [28]
Due to the nature of the selected materials, different synthetic schemes have been applied for different material families. e ceramic materials containing Y, Zr, and Nb are synthesized by a hydrothermal method, using urea decomposition at elevated temperatures for the hydrolysis of the metal ions
Summary
Nanostructured materials have reached a central role in nanomedicine, in the search of new diagnostic and therapeutic agents. One of their most attractive features is the possibility of influencing their biodistribution by surface decoration with targeting agents. NPs are used as contrast agents in bioimaging for a variety of microscopy and medical imaging methods. In small-animal imaging applications, targeted NPs are investigated as contrast agents in many modalities. NPs based on gold and other materials have been developed as alternatives to conventional contrast media for classical absorption-based X-ray imaging [3,4,5,6]. CT detection of actively targeted gold NPs against lymph nodes [14] or breast tumors [3] has been demonstrated in mice
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