PEGylated bioreducible poly(amido amine)s for non-viral gene delivery

A facile method for PEGylated bioreducible poly(amido amine)s is described by a one-pot Michael-type addition polymerization of N, N′-cystaminebisacrylamide (CBA) with a mixture of 4-amino-1-butanol (ABOL) and mono-tert-butoxycarbonyl (Boc) PEG diamine. By this approach, two Boc-amino-PEGylated p(CBA-ABOL) copolymers were obtained with the PEG/ABOL composition ratio of 1/10 (1a) and 1/6 (2a), respectively. These copolymers were characterized by 1H NMR and gel permeation chromatography. The PEGylated copolymers 1a, and its deprotected analog 1b with a terminal amino group at the PEG chain, were further evaluated as gene delivery vectors. The copolymers 1a and 1b condense DNA into nano-scaled PEGylated polyplexes (< 250 nm) with near neutral (2–5 mV, 1a) or slightly positive (9–13 mV, 1b) surface charge which remain stable in 150 mM buffer solution over 24 h. UnPEGylated polyplexes from p(CBA-ABOL), however, are relatively less stable and increase in size to more than 1 μm. The PEGylated polyplexes showed very low cytotoxicity in MCF-7 and NIH 3T3 cells and induced appreciable transfection efficiencies in the presence of 10% serum, although that are lower than those of p(CBA-ABOL) lacking PEG. The lower transfection efficiency of the PEGylated p(CBA-ABOL) polyplexes is discussed regarding the effect of PEGylation on endosomal escape of the PEGylated polyplexes.