Abstract: Objective To synthesize a biodegradable non-viral gene carrier with a high transfection efficiency and a low
cytotoxicity. Methods Poly(ethylene glycol)-block-(poly(L-glutamic acid)-graft-polyethylenimine) was prepared via
ammonolysis of poly(ethylene glycol)-block-poly (γ-benzyl L-glutamate) with the low-molecular-mass polyethylenimine (600
Da). The synthesized copolymer was characterized by 1H nuclear magnetic resonance spectroscopy and gel permeation
chromatography. The polyplex micelle from PEG-b-(PG-g-PEI) and plasmid DNA (pDNA) was studied using dynamic light
scattering, zeta-potential measurements, and gel retardation assay. The in vitro cytotoxicity and transfection efficiency of
PEG-b-(PG-g-PEI) were tested by MTT assay and luciferase assay in HEK 293T cells using PEI (25 kDa) as the control. Results
PEG-b-(PG-g-PEI) could efficiently condense DNA into nanosized particles with positive surface charges when the N/P ratio of
polymer and DNA was above 5:1. The zeta potential of the polyplexes was about 25 mV, and the particle size was 120 nm at a
N/P ratio of 10. The cell toxicity and gene transfection evaluations showed a lower cytotoxicity and a higher gene transfection
efficiency of the copolymer than PEI 25000 in HEK 293T cells. Conclusions The polymer can be used as a potential non-viral
gene carrier for gene therapy.