Superparamagnetic graphene quantum dot as a dual‐modality contrast agent for confocal fluorescence microscopy and magnetomotive optical coherence tomography.

A magnetic graphene quantum dot (MGQD) nanoparticle, synthesized by hydrothermally reducing and cutting graphene oxide‐iron oxide sheet, was demonstrated to possess the capabilities of simultaneous confocal fluorescence and magnetomotive optical coherence tomography (MMOCT) imaging. This MGQD shows low toxicity, significant tunable blue fluorescence and superparamagnetism, which can thus be used as a dual‐modality contrast agent for confocal fluorescence microscopy (CFM) and MMOCT. The feasibility of applying MGQD as a tracer of cells is shown by imaging and visualizing MGQD labeled cells using CFM and our in‐house MMOCT. Since MMOCT and CFM can offer anatomical structure and intracellular details, respectively, the MGQD for cell tracking could provide a more comprehensive diagnosis. Optical coherence tomography (OCT) is a hugely successful photonics‐based medical imaging tool; however, it lacks the spatial resolution to see individual cells. One solution to this is to tag cells with an OCT contrast agent. Here, we describe a unique OCT contrast agent. We deposit iron oxide onto the surface of nanometer‐scale graphene oxide sheet, resulting in a quantum dot nanoparticle, uniquely displaying low toxicity and strong contrast under both magnetomotive OCT and fluorescence microscopy. [ABSTRACT FROM AUTHOR]