Synthesis and characterization of polyaminoacidic polycations for gene delivery

The properties as non viral gene vector of a protein-like polymer, the alpha,beta-poly(N-2-hydroxyethyl)-d,l-aspartamide (PHEA) were exploited after its derivatization with 3-(carboxypropyl)trimethyl-ammonium chloride (CPTA) as molecule bearing a cationic group, in order to obtain stable polycations able to condense DNA. PHEA was firstly functionalized with aminic pendant groups by reaction with ethylenediamine (EDA) obtaining the alpha,beta-poly(N-2-hydroxyethyl)(2-aminoethylcarbamate)-d,l-aspartamide (PHEA-EDA) copolymer. We demonstrated that polymer functionalization degree is easily modulable by varying reaction conditions, so allowing to produce two PHEA-EDA derivatives at different molar percentage of amine groups. Subsequently, the condensation reaction of PHEA-EDA copolymers with CPTA yielded alpha,beta-poly(N-2-hydroxyethyl)(2-[3-(trimethylammonium chloride)propylamide]-amidoethylcarbamate)-d,l-aspartamide (PHEA-EDA-CPTA) polycation derivatives. In vitro studies were carried out to evaluate polycations ability to complex DNA and to protect it from nuclease degradation. Obtained results demonstrated the good ability of our new PHEA polycationic derivatives, PHEA-EDA-CPTA, to complex and condense genomic material, neutralizing its anionic charge even at very low polycation/DNA weight ratio. Finally, PHEA-EDA-CPTA polycations were characterized by in vitro cytotoxicity studies to evaluate their effects on the viability of HuH-6 human hepatocellular carcinoma cells by MTS assay. No cytotoxicity was evidenced by both polycationic derivatives after 48h of incubation at all tested concentrations.