Glyco-graphitic Carbon Nitride Nanosheets For Drug Delivery

Graphitic carbon nitride nanosheets（GCNNs）,as a two-dimensional structured nanomaterial,have the advantages of good stability,good biocompatibility,and can be modified easily.Thus,the materials can be applied to construct nano-drug delivery systems.In order to make cancer treatment more efficient,in this study,we designed three glyco-graphitic carbon nitride nanocarriers and selected CpG ODNs and doxorubicin as model drugs,which improved the therapeutic effect of the drugs.The study mainly includes the following three aspects:In system one,we designed and prepared chitosan-modified GCNNs and studied its immunostimulatory effects.Firstly,bulk graphitic carbon nitride was prepared.After exfoliation,GCNNs with a particle size of about 95 nm were obtained.The chitosan was modified on the surface of the nanosheets by electrostatic interaction to obtain CS-GCNNs nanocomposites.Characterization results showed that CS-GCNNs are uniform in size（about 120 nm）,good-dispersed,and have strong fluorescence performance.After loading cytosine（C）-guanine（G）dinucleotide-containing oligodeoxynucleus（CpG oligodeoxynucleotide,CpG ODN）,the loading capacity can reach to 45.8μg·mg^-1.MTT experiment proved the good biocompatibility of the nanomaterials.Flow cytometry and CLSM results showed that nanocarriers can improve the endocytosis ability of the drugs.This is mainly due to the endocytic pathway mediated by clathrin.What’s more,the carrier can be used as the probe of intracellular localization.The results of enzyme-linked immunosorbent assay（ELISA）showed that CS-GCNNs/CpG ODNs can improve the immune stimulating effect of macrophages.To endow nanocomposites with the ability of targeting macrophages,in system two,polyethyleneimine was modified on the surface of GCNNs,and then mannose was linked through reduction amination to obtained Man-PEI-GCNNs.Morphological tests of the carriers showed that the average particle size of the nanomaterials was about 100 nm.The results of drug loading experiments showed that the loading capacity of CpG ODNs on the carriers reached to 109.6μg·mg^-1.The cell experiment results proved that the carriers possessed low cytotoxicity,and can be used to monitor the nanocarriers in real-time.They can also greatly improve the uptake efficiency of macrophages,resulting in the greatly improved immune response effect.The receptor blocking experiment investigated the targeting ability of this material.In the third part,a liver-targeted nano-drug delivery system designed for combined therapy was constructed as system three.The adhesion ability of polydopamine made it bound to the surface of GCNNs,and galactose molecules are linked through Michael addition reaction to obtain liver-targeted Gal-PDA@GCNNs nanomaterials.The carriers had the advantages of uniform size,good photothermal and photodynamic performance,and strong loading capacity for the chemotherapy drug-doxorubicin（DOX）.The drug release results demonstrated that the carriers can quickly release the drugs under the p H condition of the tumor microenvironment.The results of flow cytometry and CLSM experiments demonstrated the targeting selectivity of the materials for hepatocarcinoma cells.While MTT and live-death staining experiments proved that the vectors combined the excellent photothermal conversion performance of PDA with the great potential of GCNNs as photosensitizers.When loaded with DOX,the system had a significant inhibitory effect on hepatocarcinoma.