Electrophoretic purification of tumor-targeted polyethylenimine-based polyplexes reduces toxic side effects in vivo.

Non-viral vectors based on polyethylenimine (PEI) are usually generated with an excess of PEI. However, the amount of unbound polymer correlates with toxicity limiting the in vivo use of these gene carriers. Purification based on size exclusion chromatography of PEI/DNA polyplexes smaller than 200 nm has been shown to efficiently remove unbound PEI polymer.

Melittin analogs with high lytic activity at endosomal pH enhance transfection with purified targeted PEI polyplexes.

Melittin-polyethylenimine (PEI) conjugates have been shown to enhance gene transfer efficiency of polyplexes due to their membrane-destabilizing properties. Inherent lytic activity at neutral pH however also provokes high cytotoxicity due to plasma membrane damage. In order to shift the lytic activity towards the endosomal membrane, several melittin analogs were designed.

Toward synthetic viruses: endosomal pH-triggered deshielding of targeted polyplexes greatly enhances gene transfer in vitro and in vivo.

Nonviral vectors should undergo "virus-like" changes compatible with the steps of gene delivery. Poly(ethylene) glycol (PEG) shielding of DNA/polycation polyplexes protects from nonspecific interactions with the extracellular environment. pH-triggered removal of the shield within the endosome may be advantageous.