Macrocyclic chelators have been widely employed in the realm of nanoparticle-based positron emission tomography (PET) imaging, whereas its accuracy remains questionable. Here, we found that 64 Cu can be intrinsically labeled onto nanographene based on interactions between Cu and the π electrons of graphene without the need of chelator conjugation, providing a promising alternative radiolabeling approach that maintains the native in vivo pharmacokinetics of the nanoparticles. Due to abundant π bonds, reduced graphene oxide (RGO) exhibited significantly higher labeling efficiency in comparison with graphene oxide (GO) and exhibited excellent radiostability in vivo. More importantly, nonspecific attachment of 1,4,7-triazacyclononane-1,4,7-triacetic acid (NOTA) on nanographene was observed, which revealed that chelator-mediated nanoparticle-based PET imaging has its inherent drawbacks and can possibly lead to erroneous imaging results in vivo.
Keywords: graphene; imaging agents; nanoparticles; positron emission tomography; radiolabeling.
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