Evaluation of a lanthanide nanoparticle-based contrast agent for microcomputed tomography of porous channels in subchondral bone.

Osteoarthritis (OA) is a chronic joint disease that causes disability and pain. The osteochondral interface is a gradient tissue region that plays a significant role in maintaining joint health. It has been shown that during OA, increased neoangiogenesis creates porous channels at the osteochondral interface allowing the transport of molecules related to OA. Importantly, the connection between these porous channels and the early stages of OA development is still not fully understood. Microcomputed tomography (microCT) offers the ability to image the porous channels at the osteochondral interface, however, a contrast agent is necessary to delineate the different X-ray attenuations of the tissues. In this study BaYbF 5 -SiO 2 nanoparticles are synthesized and optimized as a microCT contrast agent to obtain an appropriate contrast attenuation for subsequent segmentation of structures of interest, that is, porous channels, and mouse subchondral bone. For this purpose, BaYbF 5 nanoparticles were synthesized and coated with a biocompatible silica shell (SiO 2 ). The optimized BaYbF 5 -SiO 2 27 nm nanoparticles exhibited the highest average microCT attenuation among the biocompatible nanoparticles tested. The BaYbF 5 -SiO 2 27 nm nanoparticles increased the mean X-ray attenuation of structures of interest, for example, porous channel models and mouse subchondral bone. The BaYbF 5 -SiO 2 contrast attenuation was steady after diffusion into mouse subchondral bone. In this study, we obtained for the first time, the average microCT attenuation of the BaYbF 5 -SiO 2 nanoparticles into porous channel models and mouse subchondral bone. In conclusion, BaYbF 5 -SiO 2 nanoparticles are a potential contrast agent for imaging porous channels at the osteochondral interface using microCT.