Tumor accumulation of protein kinase-responsive gene carrier/DNA polyplex stabilized by alkanethiol for intravenous injection

We synthesized polymeric gene carriers consisting of poly-L-lysine (PLL) main chain modified both with substrate peptide for protein kinase Cα (PKCα) and alkanethiol (pentadecanethiol). Due to the grafted substrate peptide, the polyplex prepared from these carriers is expected to show gene expression triggered by the phosphorylation of the peptide by intracellular PKCα. The modified alkanethiol on the main chain stabilized the polyplex both via disulfide crosslinking and hydrophobic interaction. The polyplex found to show gene expression in vitro when the alkanethiol content in the main chain was enough low (4-mol%-modification of PLL's ε-amine group) to minimize cytotoxic effect. Even though the content of alkanethiol is low, the polyplex had significant stability in a model serum solution and showed longer blood circulation in vivo. The polyplex clearly accumulated in tumor after intravenous injection.