Multi-armed poly(L-glutamic acid)-graft-oligoethylenimine copolymers as efficient nonviral gene delivery vectors.
BACKGROUND
The application of polyethylenimine (PEI) in gene delivery has been severely limited by significant cytotoxicity that results from a nondegradable methylene backbone and high cationic charge density. It is therefore necessary to develop novel biodegradable PEI derivates for low-toxic, highly efficient gene delivery.


METHODS
A series of novel cationic copolymers with various charge density were designed and synthesized by grafting different kinds of oligoethylenimine (OEI) onto a determinate multi-armed poly(L-glutamic acid) backbone. The molecular structures of multi-armed poly(L-glutamic acid)-graft-OEI (MP-g-OEI) copolymers were characterized using nuclear magnetic resonance, viscosimetry and gel permeation chromatography. Moreover, the MP-g-OEI/DNA complexes were measured by a gel retardation assay, dynamic light scattering and atomic force microscopy to determine DNA binding ability, particle size, zeta potential, complex formation and shape, respectively. MP-g-OEI copolymers were also evaluated in Chinese hamster ovary and human embryonic kidney-293 cells for their cytotoxicity and transfection efficiency.


RESULTS
The particle sizes of MP-g-OEI/DNA complexes were in a range of 109.6-182.6 nm and the zeta potentials were in a range of 29.2-44.5 mV above the N/P ratio of 5. All the MP-g-OEI copolymers exhibited lower cytotoxicity and higher gene transfection efficiency than PEI25k in the absence and presence of serum with different cell lines. Importantly, the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay revealed that the cytotoxicity of MP-g-OEI copolymers varied with their molecular weight and charge density, and two of MP-g-OEI copolymers (OEI600-MP and OEI1800-MP) could achieve optimal transfection efficiency at a similar low N/P ratio as that for PEI25k.


CONCLUSIONS
MP-g-OEI copolymers demonstrated considerable potential as nonviral vectors for gene therapy.
State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, China.
Lei
L
Chen
Huayu
H
Tian
Jie
J
Chen
Xuesi
X
Chen
Yubin
Y
Huang
Xiabin
X
Jing
D000818:Animals; D016466:CHO Cells; D016923:Cell Death; D002470:Cell Survival; D006224:Cricetinae; D003412:Cricetulus; D024202:Electrophoretic Mobility Shift Assay; D016650:Fluorescein-5-isothiocyanate; D018014:Gene Transfer Techniques; D005822:Genetic Vectors / Q000235:genetics*; D006801:Humans; D042541:Intracellular Space / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy; D018625:Microscopy, Atomic Force; D010316:Particle Size; D011094:Polyethyleneimine / Q000737:chemistry*; D011099:Polyglutamic Acid / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared; D014162:Transfection; D014780:Viruses / Q000235:genetics; D014783:Viscosity
D011099:Polyglutamic Acid; D011094:Polyethyleneimine; D016650:Fluorescein-5-isothiocyanate