No abstract

Under physiological salt concentration, plasmid DNA compossible reason for this effect. Application of the small parplexed with transferrin-conjugated or unmodified polyethyticles in more concentrated form and over extended perlenimine (PEI, 800 kDa) forms huge (up to Ͼ1000 nm) iods of time improves transfection activity. Reduced intraaggregates, unless the individual components are mixed cellular release may be another explanation for the at a highly positive nitrogen/phosphate (N/P) charge ratio.decreased transfection efficiency; incubation with chloroAt low ionic strengths, however, small particles with an quine or incorporation of the endosomolytic peptide INF5 average size of 40 nm are formed over a broad range of into the small complexes enhances gene expression N/P ratios. Interestingly, in transfection experiments these approximately 10-fold. Analysis of gene expression at the small particles result in a 10-fold (B16F10 cells) to more cellular level using a green fluorescence protein reporter than 100-fold (Neuro2A cells, K562 cells) reduced lucifergene and flow cytometry revealed that the differences in ase gene expression efficiency in comparison to the large overall gene expression largely result from different intencomplexes formed in physiological salt solutions. Limited sities per expressing cell, while the difference in the pertransport of the small particles to the cell surfaces is one centage of expressing cells is less substantial.

This study presents an efficient method to remove free PEI from PEI polyplexes by SEC. Our results from transfection experiments demonstrate that free PEI substantially contributes to efficient gene expression but also mediates toxic effects in a dose-dependent manner. Purified polyplexes without free PEI have to be applied at increased concentrations to achieve high transfection levels, but exhibit a greatly improved toxicity profile.

No abstract

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. Polycation and PEG were linked via acylhydrazides or pyridylhydrazines. The pyridylhydrazone prepared from polylysine and propionaldehyde-PEG showed the greatest acid-dependent hydrolysis; at pH 5, 37 degrees C for 10 min, 90% hydrolyzed, while at pH 7.4 the half-life was 1.5 h. Particle size and zeta potential measurements of the polyplexes showed complete deshielding within 1 h at pH 5, while at pH 7.4 the shield remained at 4 h, 37 degrees C. For gene transfection a targeting conjugate was also included in the polyplex, transferrin as ligand for K562 and Neuro2A cells and epidermal growth factor for HUH-7 and Renca-EGFR cells. Marker gene expression showed that the reversibly shielded polyplexes exhibited up to 2 log orders of magnitude higher gene expression in vitro and 1 log magnitude higher gene expression in an in vivo mouse model, compared to the stably shielded control polyplexes. Engineering of polyplexes with more dynamic domains is an encouraging new direction in nonviral vector design.