Synthesis, structural characterization and in vitro testing of dysprosium containing silica particles as potential MRI contrast enhancing agents

•Dysprosium containing silica microparticles obtained by freeze and spray drying.•Higher structural units interconnection achieved in freeze vs. spray dried samples.•Dy occurance on the outermost layer of the microparticles evidenced by XPS.•Enhanced MRI contrast observed for freeze dried samples with 5% mol Dy2O3. The work is focused on synthesis and structural characterization of novel dysprosium-doped silica particles which could be considered as MRI contrast agents. Sol-gel derived silica rich particles obtained via freeze-drying and spray-drying processing methods were structurally characterized by XRD, 29Si MAS-NMR and XPS methods. The occurrence of dysprosium on the outermost layer of dysprosium containing silica particles was investigated by XPS analysis. The MRI contrast agent characteristics have been tested using RARE-T1 and RARE-T2 protocols. The contrast of MRI images delivered by the investigated samples was correlated with their local structure. Dysprosium disposal on microparticles with surface structure characterised by decreased connectivity of the silicate network units favours dark T2-weighted MRI contrast properties.