Ternary complex of plasmid DNA electrostatically assembled with polyamidoamine dendrimer and chondroitin sulfate for effective and secure gene delivery.

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 clathrin-mediated 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.