Nanoparticles electrostatically coated with folic acid for effective gene therapy.

We developed a novel vector, electrostatically coated poly(ethylenimine) (PEI)/pDNA complexes with folic acid (FA). Without covalent binding, the FA molecules could coat the PEI/pDNA complexes, and stable anionic nanoparticles were formed at a charge ratio greater than 60. The addition of FA markedly decreased the cytotoxicity of the cationic PEI/pDNA complexes to the melanoma cell line, B16-F10 cells, which regularly expressed FA-specific receptor (FR). Furthermore, the anionic FA60/PEI/pDNA complexes showed high transgene efficiency via the FR-mediated pathway in B16-F10 cells. The FA60/PEI/pDNA complexes did not show agglutination with erythrocytes. After the intravenous injection of FA60/PEI/pDNA complexes into mice, a higher transgene efficiency than PEI/pDNA complexes was observed in the liver, kidney, spleen, and lung with FR. The gene expressions of FA60/PEI/pDNA complexes were significantly inhibited by preadministration of FA. Thus, the FA60/PEI/pDNA complexes were useful for effective gene therapy.