DNA delivery systems based on copolymers of poly (2‐methyl‐2‐oxazoline) and polyethyleneimine: Effect of polyoxazoline moieties on the endo‐lysosomal escape

Abstract

Abstract Poly(2‐methyl‐2‐oxazoline)‐polyethylenimine (PMeOx‐co‐PEI) copolymers differing by degree of polymerization (DP = 50 and 200) and PEI content (from 37 to 99 mol%) were synthesized by living cationic ring‐opening polymerization of 2‐methyl‐2‐oxazoline, followed by partial hydrolysis. Upon mixing with DNA in a wide range of N/P ratios, they formed well‐defined polyplex particles of small size (typically below 100 nm) and narrow size distribution. The polyplexes demonstrated good colloidal stability and very low in vitro cytotoxicity. The copolymers exhibited buffering capacity of over 50% relative to that of the reference PEI implying effective endo‐lysosomal escape of the polyplexes. Increased cellular internalization of both PCR fragments and plasmid DNA, attributable to the strongly positive ζ potential and small size of the polyplexes, was observed. In spite of these favorable prerequisites, the transfection efficiency was low (below 20% relative to the control PEI) and was attributed to retarded swelling of the polyplex particles, endo‐lysosomal rupture, and DNA release.