Low molecular weight polyethylenimine-poly(gamma-benzyl L-glutamate) (PEI-PBLG) was crosslinked by N,N'-cystaminebisacrylamide (CBA) to get the polymer named as CBA-PEI-PBLG (CPP).CPP not only inherits PEI-PBLG's amphiphilic advantages,but also possesses reducible properties.CPP can complex with DNA to form nanoparticles.CPP/DNA complex particles were characterized by particle size and zeta potential analysis.The result showed that the complex particles have suitable size and surface charges for gene delivery.And gel retardation assay also prove CBA-PEI-PBLG has proper condensing ability for DNA.CPP has good reducible property,and also has good biocompatibility because of introducing PBLG segment.The cytotoxicity of CPP was evaluated using MTT assay,and the results showed CPP has lower cytotoxicity compared with PEI 25 K.The transfection properties were characterized in different cells by using plasmid DNA as a reporter.CPP showed higher transfection efficiencies and lower cytotoxicity in HeLa cells.This was attributed to bioreducible and biocompatibility properties of the CPP.These results suggested that CPP is a promising low-toxic,highly effective non-viral gene carrier.
GUO ZhaoPei 1,TIAN HuaYu 1,XIA JiaLiang 1,2,CHEN Jie 1,LIN Lin 1 & CHEN XueSi 1 1 Key Laboratory of Polymer Ecomaterials
To increase the in vivo stability of polycation gene carriers,a pH-sensitive shielding system,γ-benzyl L-glutamate-co-glutamate acid polymer(PGA(60)(60 refers to the molar ratio of glutamate acid in the polymer)),was synthesized and characterized.PGA(60) showed pH sensitivity at about pH 6.0.PGA(60) shielded the positive charge of DNA/PEI(1:1) complexes.Gel retardation assay showed that no DNA-strand exchange with PGA(60) occurred after PGA(60) was added to DNA/PEI complexes at different proportions.MTT cytotoxicity tests demonstrated that neither PGA(60) nor DNA/PEI/PGA(60) ternary complexes had cytotoxicity at the test concentration.The transfection efficiency was improved when the positive charge was partly shielded by PGA(60).Because of the charge repulsion between the surface of cells and ternary complex particles,there was almost no transfection efficiency when the zeta potential of ternary complexes turned to negative.Because of the suitable pH sensitive range,PGA(60) may be a potential shielding system for polycation gene carriers to be used in vivo.
