The preparing process was similar to that of aGQDs except replacing find more ammonia

with DMF. The unreacted H2O2 and water were removed by vacuum drying, and the residual DMF was removed through dialyzing for 48 h in a 3,500-Da dialysis bag. Characterization of GQDs The UV-visible (vis) spectra and fluorescence spectra were obtained using a UV–Vis spectrometer (NanoDrop, Wilmington, DE, USA) and a fluorescence spectrometer (PerkinElmer, Waltham, MA, USA), respectively. Transmission electron microscopy (TEM) observation was performed on a JEM-2100HR transmission electron microscopy (JEOL, Akishima-shi, Japan) operated at 200 kV. Fourier transform infrared (FTIR) spectra were collected using a Tensor 27 FTIR spectrometer (Bruker, Karlsruhe, Germany) in the range 400 to 4,000 cm−1. Cell culture A549 and C6 cells were cultured in Dulbecco’s modified Eagle medium (DMEM) supplemented with 10% (v/v) fetal bovine serum (FBS), penicillin (100 units/mL), and streptomycin (100 μg/mL) at 37°C in an incubator with 5% CO2 and 95% air. Cell imaging After incubated with GQDs (50 μg/mL) for 12 h, cells adhered on coverslips were washed thoroughly with PBS three times. Vactosertib supplier Formaldehyde (4%) was added to fix the cells for 20 min at room temperature. The cells without GQDs were taken

as control. The cell imaging and distribution experiment was conducted by a fluorescence microscope (Leica, Wetzlar, Germany). MTT assay The cytotoxicity of Smoothened Agonist datasheet three modified GQDs was quantitatively evaluated Lonafarnib nmr by thiazoyl blue colorimetric (MTT) assay. Cells seeded in 96-well

plates were separately treated with different concentrations (0, 10, 25, 50, 100, and 200 μg/mL) of aGQDs, cGQDs, and GQDs for 24 h. Ten microliters of MTT (5 mg/mL) was added to each well and incubated for another 4 h at 37°C. Next, 100 μL DMSO was added to each well, and the optical density at 490 nm was recorded on a microplate reader (Rayto, Shenzhen, China). Trypan blue assay Cells were seeded in 6-well plates and incubated for 24 h. GQDs modified with different functional groups were separately introduced into cells with different concentrations (0, 10, 25, 50, 100, and 200 μg/mL). The cells in the supernatant and the adherent cells were collected and washed with PBS twice after incubation with GQDs for 24 h. Next, the cells were stained with 0.04% trypan blue solution for 3 min. The live and dead cells were counted using a cytometer. Flow cytometry experiment Flow cytometry analysis was performed to detect apoptotic and necrotic cells on a FACSCanto™ flow cytometer (BD Biosciences, Heidelberg, Germany). Apoptosis or necrosis was analyzed by double staining with annexin V-fluorescein isothiocyanate (FITC) and propidium iodide (PI) according to the instructions of the manufacturer. The FITC positive control was prepared by culturing the control cells in medium containing 1% of H2O2 for 24 h.