Degradable, pH-sensitive, membrane-destabilizing, comb-like polymers for intracellular delivery of nucleic acids

This report describes the design and synthesis of a new series of degradable, pH-sensitive, membrane-destabilizing, comb-like polymers that can enhance the intracellular delivery of therapeutic nucleic acids. These comb-like polymers are based on a diblock polymer backbone where the first block is a copolymer of pH-sensitive ethyl acrylic acid (EM) monomers and hydrophobic butyl methacrylate (BMA) or hexyl methacrylate monomers. The second block is a homopolymer of N-acryloxy succinimide (NASI) or beta-benzyl L-aspartate N-carboxy-anhydride (BLA-NCA) monomers, which are functionalized to allow controlled grafting of hydrophobic HMA and cationic trimethyl aminoethyl methacrylate (TMAEMA) copolymers via acid-labile hydrazone linkages. These comb-like polymers displayed high hemolytic activity in acidic solutions, which increased with the increase in polymer concentration. All comb-like polymers degraded into small fragments upon incubation in an acidic solution (pH 5.8) due to hydrolysis of the hydrazone linkages connecting the hydrophobic/cationic grafts to the polymer backbone. Comb-like polymers successfully complexed anti-GAPDH siRNA molecules into serum- and nuclease-stable particles, which successfully silenced GAPDH expression at both the mRNA and protein levels. These results collectively indicate the potential of these new comb-like polymers to serve as vehicles for effective intracellular delivery of therapeutic nucleic acids. (C) 2010 Elsevier Ltd. All rights reserved.