Nanoparticle dynamics in macrophages investigated with a laboratory soft x-ray microscope

Silica-shell metal-core nanoparticles are gaining increasing attention as contrast agents in advanced biomedical imaging, e.g., x-ray fluorescence imaging. However, these nanoparticles often accumulate in the liver, posing a significant challenge to their delivery efficiency to the intended target. This accumulation is likely caused by macrophage activity in processing cellular waste products, invading microorganisms, and foreign nanomaterials. We employ laboratory soft x-ray microscopy to investigate the uptake and dynamics of molybdenum-core silica-shell nanoparticles (MoO2SiO2 NPs) in macrophages. A laboratory soft x-ray microscope (LSXM), capable of nanometer-scale imaging of intact cells in their near-native state, visualized the NP uptake and observed the NP localization in phagocytic organelles in cryo-fixated cells. Quantitative analysis of the size and number of intracellular phagocytic structures at different time points post NP exposure revealed MoO2SiO2 NPs' dissolution dynamics. The results were validated by fluorescence microscopy and UV-Vis spectroscopy. We conclude that the LSXM as a powerful technique for studying bio-nano interactions.