Self-assembly DNA Tetrahedron-CpG Structure Stimulate Cell Immunity

CpG motif is composed by the non-methylated cytosine and guanine deoxynucleotides, widely presenting in the genome of the bacteria and having immunostimulating action. Synthetic CpG oligo deoxyribonucleotides (CpG ODN) can simulate the immunostimulatory activity of the CpG sequence in bacteria, which may be recognized by the mammalian immune system as "exogenous threat" and then induce the body’s immune response.So, CpG ODN has potential to become a therapeutic DNA or immune adjuvant to play the role of adjuvant therapy in the treatment of common diseases and even cancer. Unmethylated CpG ODN, however, readily biodegradable, and not susceptible to cellular uptake, require repeated administration and improve the dose, which are severe restrictions for CpG applications. With the development of nanotechnology, provide a new method for medicinal CpG in vivo delivery. A large number of studies have reported that nanomaterials carried CpG showed high activity and low cytotoxicity, and biocompatibility characteristics and have the potential to become new immunosuppressive agents for the treatment and prevention of certain diseases. Different number of CpG motifs and DNA tetrahedron frame CpG-tetrahedral composite structure with different valence states. The cellular uptake rate of the composite structure, stability of the structure in cells and their immunostimulating effect were assessed. We found that the the DNA tetrahedron-CpG structure can effectively carry CpG motifs into the murine macrophage-like cells RAW264.7without transfection reagent. The structure can exist stably in the cell for8hours or more, and stimulate the cells to produce immune response. The immunostimulating enhanced with the increase of number of CpG sequences, which loaded on the tetrahedron. In addition, we also found that the the tetrahedron loaded with four CpG sequences can cause stronger immune stimulation. We realize the first time the DNA tetrahedron on drug delivery, and overcome the problems that CpG sequence is easy to be resolved and hard to be ingested by cells. We provide a new idea and method to CpG in disease prevention and treatment research and we also believe that the DNA tetrahedron structure will be a promising targeted drug carrier.