Fluorinated hydrogel nanoparticles with regulable fluorine contents and T2 relaxation times as 19F MRI contrast agents

Abstract

Medical imaging contrast agents that are able to provide detailed biological information have attracted increasing attention. Among the new emerging imaging contrast agents, 19F magnetic resonance imaging contrast agents (19F MRI CAs) are extremely promising for their weak background disturbing signal from the body. However, to prepare 19F MRI CAs with a long T2 relaxation time and excellent biocompatibility in a simple and highly effective strategy is still a challenge. Herein, we report a new type of 19F MRI hydrogel nanocontrast agents (19F MRI HNCAs) synthesized by a surfactant-free emulsion polymerization with commercial fluorinated monomers. The T2 relaxation time of 19F 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 19F MRI signal intensity, the 19F MRI signal intensity was not only determined by the fluorine content in 19F MRI HNCAs but also by the hydration microenvironment around the fluorine atoms. Moreover, 19F MRI HNCAs demonstrated excellent biocompatibility and imaging capability inside cells. The primary exploration demonstrated that 19F MRI HNCAs as a new type of 19F MRI contrast agent hold potential for imaging lesion sites and tracking cells in vivo by 19F MRI technology.