OBJECTIVE:To study the cytotoxicity of the graft polymer after polyethyleneimine (PEI) had been modified by polyoxyethylene stearate (POES) and the property of the carrier,grafted-polymer/DNA complexes. METHODS: To modify PEI by conjugating PEI to POES with succinimidyl carbonate method. Structural analysis of synthesized polymer was performed by using 1H-NMR. Agarose gel electrophoresis (AGE) behavior of the graft polymer/DNA complexes was observed with particle size and zeta potential measured. The cytotoxicity of the graft polymer was evaluated by MTT method. The pGL3-lus served as a reporter gene,and the luciferase activity was determined to evaluate the transfection efficiency of grafted-polymer/DNA on Hela cells. RESULTS: 1H-NMR showed that the graft polymer had high purity. AGE showed that the DNA-wrapping ability of the graft polymer were increased with the increase of N/P ratios,and decreased with the increase of the POES graft number. The size of complexes was below 300 nm,and the zeta potential of the complexes increased with the increase of N/P ratios. The graft polymer showed significantly lower cytotoxicity than PEI. The graft polymer with lower POES graft number had higher transfection efficiency. CONCLUSIONS: The POES-modified PEI can be used as an effective non-viral genetic carrier.

Objective To modify polyethyleneimine (PEI) by using Poloxamer 188 (P188) , and evaluate its related feature as carriers of genes in vitro. Methods PEI was modified through conjugating one hydroxyl group of P188 to the amino group of PEI by carbonate method. Structural analysis of synthesized polymer was performed by using 1H-NMR. The particle size and Zeta potential of synthesized polymer /DNA complexes were measured. The cytotoxicity of the complexes was evaluated using MTT method in MCF-7 cells, HeLa cells and HepG2 cells. The pGL3-lus was used as a reporter gene, and the transfection efficiency of complexesat HeLa cells was evalutated by measuring activity of luciferase. Results The result of 1H-NMR showed the purity of these synthesized polymers was high. The particle size of complexes were decreased with the increment of N /P ratios. The Zeta potential of complexes increased with the increment of N /P ratios. The cytotoxicity of the complexes increased with the increment of N /P ratios. The synthesized polymers showed lower cytotoxicity than unmodified PEI. The new synthesized polymers had maintained the high transfection efficiency at high N /P ratios. In particular, the optimal transfection efficiency of (P188) 1- PEI (N /P = 24) was significantly higher than that of PEI (N /P = 6) . Conclusion The P188 modifed PEI can serve as a effective non-viral gene carriers to transfect Hela cells.