DCs were then collected and suspended in cold staining buffer (PBS containing 1% FCS, 0.1 mL) in microcentrifuge tubes. Afterwards, 20 μL of FITC-labeled anti-CD83, CD86, and HLA-DR monoclone antibodies (BD Pharmingen, San Jose, CA, USA) were added and Nutlin-3 concentration incubated with DCs for 30 min at 4°C. The DCs were washed again with cold staining buffer for three times, and the cell surface markers were analyzed by flow cytometry. Cellular viability study The influence of GO on DC viability was checked with

a standard MTS cell viability assay according to the manufacturer’s direction. Briefly, DCs were treated with GO (0.1 μg/mL) or D-Hank’s solution in 24-well plates for 2 h at 37°C in 5% CO2, washed thoroughly, and then added into 96-well plates with a density of 1 × 104/well. After 1, 4, and 24 h of incubation, the viability of DCs was evaluated with the MTS cell viability Selleck Seliciclib assay (n = 6). Statistical analysis Statistical difference was determined by Student’s t test, and a value of p < 0.05 was considered statistically significant. Results GO was prepared from natural graphite by a modified Hummer's method [24]. In order to get exfoliated single-layer nanosized GO, the GO solution was further processed and cracked by ultrasonication. The GO nanosheets were next collected via centrifugation at 50,000 g and dispersed in water as the stock solution. Atomic force microscopy (AFM) characterization (Figure 1A)

provided morphological information of the GO nanosheets. The height profile showed that the thickness of GO nanosheets was around 1.1 nm (Figure 1A), indicating single-layer

nanosheets. Moreover, the lateral size of GO nanosheets was about 60 to 360 nm, with an average dimension of 140 nm. The GO was negatively RG-7388 supplier charged with an average zeta potential of -28 mV (Figure 1B). The GO solutions were used without further treatments in the following experiments. Figure 1 Characterization of GO nanosheets and their antigen loading capability. (A) AFM topographic image of nanosized GO sheets deposited on mica (top) and the height profile along the black line (bottom). Scale bar is 500 nm. (B) Distributions of size and zeta potential of GO. (C) Loading rates of Ag on GO at various peptide/GO feed ratios. Immune system To induce a specific anti-glioma immune response, DCs must be exposed to glioma antigens. The antigen used in the study was a peptide (ELTLGEFLKL, termed Ag) from the protein survivin, which is widely expressed in malignant gliomas [20–22]. Survivin is a member of the inhibitor of apoptosis (IAP) protein family, which can regulate two important cellular processes: it inhibits apoptosis and promotes cell proliferation. Hence, survivin expression is generally associated with poor prognosis [30, 31]. The peptide ELTLGEFLKL can bind to HLA-A*0201, the most common human leukocyte antigen (HLA) serotype, and stimulate DCs to generate CD8+ immune responses against glioma cells [20–22, 26].