Figure 2 TEM images of three modified GQDs deposited on copper grids. (a) The TEM image of aGQDs. (b) Diameter distribution of the cGQDs. (c) The TEM image of dGQDs. As shown in Figure 3, in the aGQDs FTIR spectra, the peak at 1,627 cm−1 was attributed to the vibration of C = O bonds. The peak centered at 1,417 cm−1 was assigned to the bending vibrations of N-H

bonds, while the peak at 1,328 cm−1 was attributed to the bending vibrations of C-N bonds, indicating that the amide functional groups had been successfully grafted onto the graphitic sheet. The FTIR spectra of cGQDs showed absorption of carboxyl group and hydroxyl group, as evidenced by the COO− symmetric stretching vibration at 1,388 cm−1 https://www.selleckchem.com/products/i-bet-762.html and the COO− antisymmetric

stretching vibration at 1,571 cm−1[6, 9]. In comparison with GO, two new peaks (1,400 and 1,304 cm−1) ascribed to the stretching vibration of selleck C-N band emerged in the FTIR spectra of dGQDs, which implied that the CO-N (CH3)2 groups had been incorporated in the GQDs. Figure 3 FTIR spectra of the GQDs. The FTIR spectra of three modified GQDs and GO. The cell uptake and distribution of GQDs The photoluminescent properties of the GQDs allow us to monitor their cellular uptake and distribution directly. GQDs uptake and bioimaging experiments were performed with a fluorescence microscope. In comparison with the control cells (Figure 4a) without GQDs that had been incubated for the same time, the fluorescence of the cells incubated with 50 μg/mL of modified GQDs (Figure 4b,c,d) for 12 h was obviously brighter, which indicated the cell uptake of GQDs with

different chemical groups. The majority of the fluorescence intensity was raised from the cytoplasm, demonstrating that the three modified GQDs were located in the cytoplasm but not in the 4-Aminobutyrate aminotransferase nucleus. No obvious reduction in fluorescence brightness was observed under continuous excitation over 20 min, indicating the high photostability of three kinds of modified GQDs. Figure 4 Representative fluorescence microscope images of cells. (a) Fluorescence image describing control cells. (b) Cells treated with 50 μg/mL of aGQDs for 12 h. (c) Cells exposed to 50 μg/mL of cGQDs for 12 h. (d) Cells after the treatment of 50 μg/mL of dGQDs for 12 h. Magnification, ×20. Cell selleck inhibitor proliferation evaluation Figure 5a showed that after 24-h exposure to aGQDs, the cell proliferation of A549 cells exhibited a concentration-dependent decrease. A significant cell proliferation decrease was induced by aGQDs when the concentration reached 100 and 200 μg/mL compared to that of the control cells (p < 0.05). When the concentration of cGQDs reached 50 μg/mL, the cell MTT (% of control) was statistically different from the control groups (p < 0.05). The influence of dGQDs on A549 cell proliferation was statistically significant only when the concentration was 200 μg/mL (p < 0.05).