Quantitative Nanoscopy of Small Blinking Graphene Nanocarriers in Drug Delivery

Nanotechnology-enhanced drug delivery via receptor-mediated endocytosis provides a promising and clinically translatable strategy to targeted diagnosis and precise therapy, yet an in-depth understanding of this process is technically limited by our inability to probe the nanocarrier distributions at the cell surface and inside the cell at nanoscale resolution. Here, we report small blinking single-layer graphene oxide nanosheet (GONS) that  serves both as a nanoscopy fluorophore and as a drug-bearing nanocarrier for addressing such a task. The GONS blinks spontaneously with a low duty cycle (∼0.003), high photon output (∼3000 photons per switching event), and higher photostability than organic dyes, thus affording well for single molecule localization-based super-resolution imaging. Applying the localization analysis, we reveal GONS clustering size, GONS number in each cluster, and the number fraction of GONSs that participate in clustering at the cell surface and in the cytoplasm, respectively, and track their evolutions over 24 h. The data suggest that the nanocarrier clustering and distribution at the cell surface control their endocytosis and accumulation inside the cell. This process is drug-independent during which drug transportation into the destination relies on its own loading and escaping capability. Thus, this work demonstrates the great potential of the dual-functional GONS in quantitative super-resolution imaging of drug carriers in cells, which is helpful for the rational design of a smart drug delivery system aiming at achieving full therapeutic capacity.