Highly water-dispersible calcium lignosulfonate-capped MnO nanoparticles as a MRI contrast agent with exceptional colloidal stability, low toxicity and remarkable relaxivity.

A simple and efficient method to synthesize highly water-dispersible calcium lignosulfonate-coated manganese oxide nanoparticles as a potential candidate for the current magnetic resonance imaging (MRI) contrast agents was reported. Hydrophobic MnO nanoparticles with dimensions of about 10 nm were prepared by thermal decomposition of manganese(ii)acetylacetonate in the presence of oleic acid as a surfactant. The characteristics of the synthesized nanoparticles, cytotoxicity assay and MRI properties were investigated in detail. Results showed that calcium lignosulfonate has a great influence on the colloidal stability and biocompatibility of MnO nanoparticles in water. Furthermore, this coating agent ensures abundant exposure of external Mn ion with protons of water, which endows the nanoparticles with a longitudinal molar relaxivity ( ) of 4.62 mM s. An efficient contrast enhancement effect was observed in the study of MRI investigations.