PEGylation of poly(amine-co-ester) polyplexes for tunable gene delivery

There is growing interest in PEGylation of cationic polymeric vehicles for gene delivery in order to improve vehicle stability and reduce toxicity, but little is known about the effects of PEG coatings on transfection. We used a polymer from the poly(amine-co-ester) (PACE) family blended with PEG-conjugated PACE at different ratios in order to explore the effects of polyplex PEGylation on the transfection efficiency of plasmid DNA, mRNA, and siRNA in vitro and mRNA in vivo. We discovered that concentrations of PACE-PEG as low as 0.25% by weight improved polyplex stability but also inhibited transfection in vitro. In vivo, the effect of PACE-PEG incorporation on mRNA transfection varied by delivery route; the addition of PACE-PEG improved local delivery to the lung, but PEGylation had little effect on intravenous systemic delivery. By both delivery routes, transfection was inhibited at concentrations higher than 5 wt% PACE-PEG. These results demonstrate that excess PEGylation can be detrimental to vehicle function, and suggest that PEGylation of cationic vehicles must be optimized by PEG content, cargo type, and delivery route.