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.
Chen
Lei
L
State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, China.
Tian
Huayu
H
Chen
Jie
J
Chen
Xuesi
X
Huang
Yubin
Y
Jing
Xiabin
X
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