Synthesis and evaluation of poly(ethylene glycol)-polylysine block copolymers as carriers for gene delivery

Different types of poly(ethylene glycol)-poly(L-lysine) PEG-PLL block copol ymers were examined for their ability to form polyelectrolyte complexes wit h DNA, their toxicity toward red blood cells and their in vitro transfectio n efficiency. The complexation of the polymers with DNA was studied using t he ethidium bromide fluorescence technique. All polymers complexed DNA to f orm particles with sizes ranging from 80 nm to 150 nm. In most cases, small er particles were also observed, and sometimes populations of even larger p articles could be detected. In vitro toxicity toward red blood cells Mi as low. Agglutination of red blood cells with some of the noncomplexed block c opolymers was observed, but the aggregates were less dense than with polyly sine. Transfection efficiency of 293 cells in vitro in the presence of chlo roquine was dependent upon the charge ratio of polymer/DNA. Efficient trans fection was achieved for the PEG-PLL block copolymers with linear PLL block s. On the other hand, very low transfection efficiency was obtained from th e PEG-PLL with a dendritic PLL block.