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Novel triblock copolymers of poly (L-lactide)-poly (ethylene glycol)-sebacate-poly (ethylene glycol)-poly (L-lactide) were synthesized by Ring-Opening Polymerization of different ratios of L-lactide with other three pre-prepared poly (ethylene glycol)sebacate-poly (ethylene glycol) polymers, coded A, B and C which had different poly (ethyleneglycol) chain lengths. The copolymers were characterized by FTIR and 1 H NMR spectroscopy, which indicated that the reaction of ROP took place and led to producing nine triblock copolymers having new different lactide chain lengths (n = 10, 25 and 50), AL 10 , AL 25 , AL 50 ,BL 10 , BL 25 , BL 50 , CL 10 , CL 25 , and CL 50. Nine polymer networks were also prepared from copolymers with sodium alginate S 1-S 9 and finally mixed with a solution of hydroxyl ethyl cellulose to form SH 1-SH 9 .

Introduction: Chitosan is one of the natural polymers can generally consider as a biocompatible and biodegradable polycationic polymer, which has minimum immunogenicity and low cytotoxicity. Therefore, chitosan and its derivatives may represent potentially safe cationic carriers for use in gene delivery.Materials and Methods: Chitosan with 90.1 DD% obtained by deacetylation of chitin extracted from local shrimp shells. Graft copolymerization of L-lactide onto chitosan was carried out at room temperature by ring opening polymerization under a nitrogen atmosphere to prepare chitosan-g-poly (N-lactide) graft copolymer. It was obtained in good yield and characterized by FTIR. The samples purity and concentration were detected using both Nanodrop UV-spectroscopy and agarose gel electrophoresis techniques. The human heat shock proteins gene, hsp-70, was used as a model of human genes to study the effect of chitosan-g-poly(N-lactide) graft copolymer. Results and Discussion: The results revealed that chitosan-g-poly (N-lactide) graft copolymers had safety effect on the DNA, and binding with it. the human heat shock proteins gene, hsp-70, was used as a model of human genes to study the effect of chitosan-g-poly(N-lactide) graft copolymer, it shows a good binding ability the human gene, implies that it might be used in biomedical applications in the future. Conclusions: Grafting of L-lactide onto chitosn by ring opening polymerization was confirmed by FTIR.   The repaired polymer has safety effects on human DNA and genes. The chitosan-g-poly (N-lactide) graft copolymer has shown high efficiency to electrostatic interaction with human DNA and gene, implying that it is suitable to be used as DNA and gene delivery.

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