Novel Synthetic Method and Characterization of Magnetic Resonance/Near-infrared dual-modal imaging agents by In Vivo Molecular Imaging

A novel magnetic resonance (MR)/near-infrared (NIR) imaging contrast agent was developed by a facile fluorescent dye-coating on magnetic nanoparticles (MNP). The fluorescent dye molecules were directly attached onto the... [ view full abstract ]

A novel magnetic resonance (MR)/near-infrared (NIR) imaging contrast agent was developed by a facile fluorescent dye-coating on magnetic nanoparticles (MNP). The fluorescent dye molecules were directly attached onto the nanoparticle surface, which enable the nanoparticles to transfer from hydrophobic phase to hydrophilic phase. This facile synthesis method was applied to various fluorescent dyes and another hydrophobic nanoparticle to evaluate the synthetic principle. And the dye coating on the particle was well characterized by single particle imaging technique. We also demonstrated that photostability of fluorescent dyes on the particle surface were improved compared to the soluble dye form by monitoring of fluorescence signals under the continuous irradiation.
The dye-coated MNP presents high T2 relaxivity value (308 mM-1s-1), good cell viability due to biocompatible NIR dye, indocyanine green, supporting non-invasive in vivo MR/NIR imaging. We performed in vivo tracking of the dye-coated MNP labeled dendritic cells (DCs). Importantly, the migration of DCs via lymphatic drainage and homing into the lymph node were monitored through real-time NIR fluorescence and MR imaging. This novel MR/NIR contrast agent has potential applications as a non-invasive imaging agent for imaging or tracking of immune cells to confirm immunotherapeutic efficacy.