Polysaccharides Functionalized Graphene Oxide As Carriers For CpG ODN

Synthetic oligodeoxynucleotides(ODN)containing unmethylated cytosine and guanine(CpG)motifs can mimic the immunostimulatory effects of bacterial DNA and activate a similar innate and adaptive immune responses.Therefore,CpG ODNs have become a promising immunotherapeutic agent for the treatment of various diseases,including cancer,allergy and infectious diseases.However,the naked CpG ODN is easily degraded by nuclease and shows low cellular uptake,which greatly limits its applications.In this study,we developed CpG ODN delivery systems based on chitosan(CS)and yeast ?-glucan functionalized graphene oxide(GO).After studying the properties of polysaccharides functionalized GO,their ability as carriers for delivery of CpG ODN into RAW264.7 cells and the in vitro immunostimulatory activity of polysaccharides-GO/CpG ODN were further studied.The results showed that CS functionalized GO possessed smaller size,positively charged surface and good biocompatibility.CS functionalization also significantly reduced the nonspecific proteins adsorption on GO,which improved its safety for biomedical applications.Moreover,the GO-CS complex could evidently activate RAW264.7 cells to secret more amount of cytokines,which showed strong potential as an adjuvant.In addition,GO-CS improved the loading capacity of CpG ODN and promoted the cell uptake of CpG ODN.GO-CS/CpG ODN complexes could significantly enhance the secretion of interleukin-6(IL-6)and tumor necrosis factor ?(TNF-?)from RAW264.7 cells.Therefore,GO-CS nanocomposites could be used as carrier for CpG ODN and effectively deliver it into macrophages.In addition,based on the recognition of yeast ?-glucan and Dectin-1,yeast ?-glucan was used as targeting moiety for immune cells in constructing CpG ODN delivery systems.The results indicated that yeast ?-glucan functionalized GO had lower nonspecific proteins adsorption and could promote the proliferation of RAW264.7 cells.Moreover,yeast ?-glucan functionalization could significantly enhanced the cellular uptake of CpG ODN.Compared with GO-?-glucan and GO/CpG ODN,GO-?-glucan/CpG ODN complexes exhibited the strongest immunostimulatory effect,leading to the enhanced secretion of cytokines(IL-6 and TNF-?).In summary,polysaccharides functionalized GO could serve as efficient nanocarriers for enhancing the delivery efficiency of CpG ODN,which will facilitate the applications of CpG ODN in vaccines and immunotherapy.