Abstract
The purpose of this study was to prepare polymeric gene carriers based on PEOz-b-PMAA, (poly(2-ethyl-oxazoline)- block-poly -methacrylic acid) and Branched-Poly (ethylenimine), (B-PEI). PMAA were partially dissociation under neuteral pH and were with negative charge, so that they could attach to the positive charge surface of B-PEI/DNA polyplex. The newly formed polyplex were biocompatible by the hydrophilic segment, PEOz and could enhance the stability of the polyplex in vivo. We prepared B-PEI/DNA polyplex by varying weight ratio of B-PEI/DNA, till the polyplex were provide with stable particle size and highly positive charge. And the B-PEI/DNA polyplex were then formed a bilayer structure polyplex with PEOz-b-PMAA. The experiment results showed that the particle size of B-PEI/DNA polyplex were about 150 nm, and the bilayer polyplex were about 200~250nm. While B-PEI/DNA polyplex carried posive surface charge with zeta potential of 30mV, the PEOz-b-PMAA could covered up the positive charge of B-PEI when bilayer structure polyplex were prepared. Data of material cytotoxicity showed that B-PEI revealed extremely toxicity to Hela cells under 100μg/ml concentration, and the cells viability approached 0, and PEOz-b-PMAA showed 80% viability under the same conceration. Then We compared the viability of B-PEI/DNA and PEOz-b-PMAA /B-PEI/DNA, and the later kept higher viability then the former . TEM observation showed that PEOz-PMAA/B-PEI/DNA polyplex formed core-shell structure, and the polyplex in pH 5 would collapse and release plasmid.The results of transfection effects indicated that the bilayer structure reduce the efficiency slightly, and RLU/unit weight of the bilayer gene carrier were about 1/10~1/100 of B-PEI/DNA polyplex. By CLSM observation, we observed celluptake of B-PEI/DNA polyplex and bilayer structure polyplex, the result revealed that the bilayer structure polyplex started to accumulate after 3hrs incubation and accumulated a significant amount after 6hrs. In conclusion, the polyplex formed with PEOz-PMAA covered on B-PEI/DNA could improved the cytotoxicity of B-PEI/DNA. The newly ternary polyplex presented a well transfection efficiency and cell uptake efficiency, so the ternary polyplex constitute a useful approach for further design of gene carriers.