A novel magnetic fluorescent biosensor based on graphene quantum dots for rapid, efficient, and sensitive separation and detection of circulating tumor cells

We describe a “turn-on” magnetic fluorescent biosensor based on graphene quantum dots (GQDs), Fe 3 O 4 , and molybdenum disulfide (MoS 2 ) nanosheets. It is used for rapid, efficient, and sensitive separation and detection of circulating tumor cells (CTCs). A facile approach (electrochemical synthesis method) for the preparation of photoluminescent GQDs functionalized with an aptamer [epithelial cell adhesion molecule (EpCAM) receptors] and a magnetic agent for one-step bioimaging and enrichment of CTCs is described. MoS 2 nanosheets, as a fluorescence quencher, and the aforementioned aptamer@Fe 3 O 4 @GQD complex were assembled to construct “turn-on” biosensing magnetic fluorescent nanocomposites (MFNs). This system exhibits low cytotoxicity and an average capture efficiency of 90%, which is higher than that of other magnetic nanoparticles on account of the one-step CTC separation method. In addition, the MFNs could quickly identify and label CTCs within 15 min, surpassing other one-step and two-step marker detection methods. Furthermore, because of the presence of aptamers, the MFNs have specific capability to capture CTCs (both low- and high-EpCAM-expressing cells). In addition, high-sensitivity detection of up to ten tumor cells in whole blood was achieved. Therefore, the MFNs have great potential to be used as universal biosensing nanocomposites for fluorescence-guided tumor cell enrichment and bioimaging. ᅟ