Fig. 4

Confocal microscopy showing cellular uptake, localization and exocytosis of s-GOs and l-GOs in HK-2 cells. a Images of cellular uptake of FITC labelled (green) s-GOs and l-GOs after 4 and 24 h coculture. The nucleus was stained with DAPI (blue). b Quantitatively analysis of uptake of s-GOs and l-GOs in HK-2 cells. c Quantitative analysis of GO internalized in cells after 24 h treatment of s-GOs and l-GOs compared to untreated group by flow cytometry d Subcellular colocalization analysis of s-GOs-FITC/l-GOs-FITC and LysoTracker Red in HK-2 cells after 24 h coculture. The nucleus was stained with DAPI (blue). The second line images of each GO-treated group show higher magnification of a cell. e Profiles of fluorescence signal intensity along the straight line (white) crossing the nucleus and lysosome of a representative s-GO/l-GO treated cell. f Exocytosis of s-GOs and l-GOs from HK-2 cells after GO-treated cells cultured in GO-free medium for 24 h. g Quantitatively analysis of s-GO or l-GO exocytosis from HK-2 cells. Scale Bar: 20 μm; intra: intracellular; extra: extracellular. ***p < 0.001