Synthesis, DNA Condensation, Cell Transfection Of Cobalt (Ⅱ)-polybenzimidazole Complexes

Gene therapy is a broad term that encompasses any strategy to treat a disease by introducing exogenous gene into cells of an affected person. Therefore, research efforts are currently focused on designing effective carrier vectors that can protect and transfer exogenous gene into the patient’s cells for gene therapy. Now, providing effective, targeted and safe carriers is a major challenge for gene delivery. In this work, we chosed bis(benzimidazol-2-ylmethyl)amine (IDB), tris(benzimidazol-2-ylmethyl)amine(NTB), N,N,N’,N’-tetrakis(benzimidazol-2-ylmethyl)-1,2-ethanediamine (EDTB) and 1,1,4,7,7-pentakis(1H-benzimidazol-2-ylmethyl)-1,4,7-triazaheptane (DTPB) as primary ligands, and based on which we synthesized eight Co(Ⅱ)-polybenzimidazole (pbzim) complexes. We systematically discuss the efficiency of Co(Ⅱ) complexes for gene delivery.Firstly, the Co(Ⅱ) complexes were characterized by X-ray diffraction and elemental analysis. Then, we used UV-vis absorption titration to examine the DNA-binding affinity of the complexes. The results suggest that the affinity is enhanced as the number of positive charges and bzim groups rise.Secondly, the property of condensates which formed at various molar ratios of complexes to DNA was examined by means of EMS A, RALS, DLS and TEM. The results show that the size, surface charge, and morphology of the condensates generated via a complex dose-dependent process can be controlled by selection of different complexes. We also found that DNA could be released from the condensates at acidic environment, and the EDTA and NaCl could accelerate the dissociation of DNA condensates.Finally, the cytotoxicity of Co(Ⅱ) complexes and DNA condensates were separately evaluated by MTT assay. The results indicate that the cytotoxicity of condensates is lower than that of complexes, and the cytotoxicity of both complexes and their condensates enhance with increasing number of positive charges and bzim groups. Moreover, the imaging examination performed under fluorescence microscope indicates that the condensates are in favor of cell internalization, and the genes transferred by the condensates are efficiently expressed.