4.5.1 Paramagnetic Ions Coordinated Graphene
Iron (Fe), manganese (Mn), and gadolinium (Gd) are representative paramagnetic
metal ions with high magnetic moments. When these ions coordinate surrounding
water molecules, the spin-lattice relaxation (T1) efficiently occurs. Since the T1
contrast depends on the net magnetization with respect to time, these ions can be
employed as adequate T1 contrast agents [69]. Nevertheless, as highly paramagnetic metal ions typically exhibit high toxicity owing to the random coordination
with biomolecules, these ions are mostly used as chelated forms [68]. To that end,
functionalized graphene derivatives with cavities and oxygenated functional groups
Fig. 4.5 Dynamic tracking of protein of interest. a Confocal fluorescence images of insulin
conjugated GQDs (green, left) or with antibodies against insulin receptor (IR) (red, middle). b and
c Cellular distribution of insulin receptors after (b) 10 min or (c) 1 h incubation with
insulin-GQDs. Scale bar = 10 lm. Adapted with permission [66]
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