Two-photon graphene quantum dot modified GdO nanocomposites as a dual-mode MRI contrast agent and cell labelling agent.

For obtaining high-resolution macroscopical anatomical information and high sensitivity microscopical optical signals, it is highly desirable to develop dual-modality magnetic resonance imaging (MRI) and fluorescent probes in medical imaging simultaneously. In this study, GdO nanoparticles were modified with two-photon graphene quantum dots (GQD), integrating a magnetic resonance imaging (MRI) contrast agent with two-photon imaging functionality into one nanoprobe. A photoluminescence study indicated that the GQD modification process integrated MRI properties with both one-photon and two-photon imaging properties. GdO/GQD nanocomposites showed a significantly improved longitudinal relaxivity (r = 15.995 mM s) in comparison with commercial Magnevist (Gd-DTPA, r = 4.5 mM s) and some reported papers. Excellent water solubility and good biocompatibility make GdO/GQD nanocomposites an ideal dual-modal imaging agent, suggesting their potential and significant biological and clinical applications in the future.