A pH Responsive Ternary Gene Carrier based on Branched- Poly(ethylenimine) and Poly(2-ethyl-2-oxazoline)-block- Poly(methacrylic acid)

Abstract

This study demonstrates new ternary polyion gene carriers, based on the P H -responsive diblock copolymer poly(2-ethyl-oxazoline)-block-poly(methacrylic acid) (PEOz-b-PMAA), and the branched-poly (ethylenimine) (B-PEI). This study complexes the plasmid DNA with B-PEI and further with PEOz-b-PMAA to obtain ternary polyplexes (DNA/B-PEI/PEOz-b-PMAA). PMAA were partially dissociated under neutral P H with a negative charge, to attach to the positive charge surface of the B-PEI/DNA polyplex. The ternary polyplexes will also desorb and return to the original pre-poly complex to help gene release after cell uptake due to PMMA become neutral charge under an acid environment in endosome. The ternary polyplexes showed suitable mean particle size, low cytotoxicity, and acceptable transfection at P H 7.4 because of shielding of B-PEI by PEOz-b-PMAA. TEM morphology showed that the stable core-shell structure of ternary polyplexes at P H 7.4 collapsed and released plasmid at P H 5. Observations of cell uptake of the B-PEI/DNA polyplex and ternary polyplexes by CLSM revealed that ternary polyplexes started to accumulate after 3 h incubation and accumulated significantly after 6 h. In conclusion, the ternary polyplex improves cytotoxicity of the single B-PEI/DNA polyplex, and presents a PH-responsive behavior to enhance gene escape from the polyplex. The ternary polyplex constitutes a useful approach for gene carrier design.