The purpose of this study was to develop a ternary complex of plasmid DNA (pDNA) electrostatically assembled with polyamidoamine (PAMAM) dendrimer and chondroitin sulfate (CS) for effective and secure gene delivery. PAMAM dendrimers are new cationic polymers that are expected to be used as gene delivery vectors. However, cationic non-viral gene vectors showed cytotoxicity by binding to negative cellular membranes. We therefore prepared a ternary complex by adding CS, an anionic polymer, and examined its usefulness. The pDNA/PAMAM dendrimer complex (PAMAM dendriplex) and the PAMAM dendriplex coated by CS (CS complex) showed nanoparticles with positive ζ-potential and negative ζ-potential, respectively. The CS complex had no cytotoxicity against B16-F10 cells and no agglutination activity, although severe cytotoxicity and high agglutination were observed in the PAMAM dendriplex. As a result of an in vitro gene expression study of B16-F10 cells, not only the PAMAM dendriplex but also the CS complex showed high transfection efficiency. The transfection efficiency of the CS complex was significantly inhibited by clathrinmediated endocytosis inhibitor (chlorpromazine), caveolae-mediated endocytosis inhibitor (genistein), and hypothermia. Tail-vein injection of the CS complex into mice led to significantly higher gene expression in the spleen than the PAMAM dendriplex. Thus, the ternary complex of pDNA electrostatically assembled with PAMAM denriplex and CS showed safe high gene expression in the spleen. This vector is expected to be useful for useful gene delivery.Key words ternary complex; chondroitin sulfate; polyamidoamine dendrimer; gene delivery Gene therapy is expected to be an effective method to treat cancer, infection, innate immunodeficiency and cardiovascular diseases.1-4) The success of gene therapy is largely dependent on the development of vectors capable of effectively delivering foreign genes into targeted cells. One major approach in gene therapy is based on cationic polymers, such as polyethylenimine (PEI), polylysine, polyarginine, and chitosan.5-8) When cationic polymer-encapsulated plasmid DNA (pDNA) makes association with the cell surface, it enters the cells by endocytosis.Polyamidoamine (PAMAM) dendrimers are new cationic polymers, which are highly branched radial polymers that have specific and systematically variable size, shape and chemical structure. Their radical structure contains a 2-carbon ethylenediamine core and primary amino groups on the surface. Successive generations (G) have increasing diameter and double the surface functional amino groups of the preceding generation.9,10) PAMAM dendrimers can be used as carriers for pDNA and show high transfection efficiency. 11,12)The pDNA/PAMAM dendrimer complexes (PAMAM dendriplex) are formed by electrostatic interactions and initiate cell entry through binding to anionic phospholipids on the cell membrane. With increasing generations of dendrimers, the PAMAM dendriplex showed higher transfection efficiency, which depended on the charge rati...

The purpose of the present study was to investigate the usefulness of the ternary complex with protamine and γ-polyglutamic acid (γ-PGA), which are biodegradable materials for foods and medical products, as a safe gene delivery vector. We formed cationic binary complexes (plasmid DNA (pDNA)/protamine complexes) with high transfection efficiency. The binary complex showed slight toxicity probably related to its total cationic charge. Then, we formed ternary complexes (pDNA/protamine/γ-PGA complexes) by addition of anionic polymer, γ-PGA, and they showed no cytotoxicity. The transfection efficiency of the pDNA/protamine/γ-PGA complexes was as high as that of the pDNA/protamine complexes, although their zeta potentials were different. Inhibition study of the gene expressions in B16-F10 cells suggested that pDNA/protamine complexes were taken up by caveolae-mediated endocytosis and macropinocytosis. On the other hand, pDNA/protamine/ γ-PGA complexes were taken up by clathrin-mediated endocytosis and macropinocytosis. Thus, we succeeded in developing the ternary complex as a safe gene delivery vector with biocompatible materials.