Fluorinated hydrogel nanoparticles with regulable fluorine contents and T(2) relaxation times as (19)F MRI contrast agents

Medical imaging contrast agents that are able to provide detailed biological information have attracted increasing attention. Among the new emerging imaging contrast agents, (19)F magnetic resonance imaging contrast agents ((19)F MRI CAs) are extremely promising for their weak background disturbing signal from the body. However, to prepare (19)F MRI CAs with a long T(2) relaxation time and excellent biocompatibility in a simple and highly effective strategy is still a challenge. Herein, we report a new type of (19)F MRI hydrogel nanocontrast agents ((19)F MRI HNCAs) synthesized by a surfactant-free emulsion polymerization with commercial fluorinated monomers. The T(2) relaxation time of (19)F MRI HNCA-1 was found to be 25–40 ms, guaranteeing its good imaging ability in vitro. In addition, according to an investigation into the relationship between the fluorine content and (19)F MRI signal intensity, the (19)F MRI signal intensity was not only determined by the fluorine content in (19)F MRI HNCAs but also by the hydration microenvironment around the fluorine atoms. Moreover, (19)F MRI HNCAs demonstrated excellent biocompatibility and imaging capability inside cells. The primary exploration demonstrated that (19)F MRI HNCAs as a new type of (19)F MRI contrast agent hold potential for imaging lesion sites and tracking cells in vivo by (19)F MRI technology.