Degradable copolymer based on amphiphilic N-octyl-N-quatenary chitosan and low-molecular weight polyethylenimine for gene delivery

Chengchu Liu,^1,2,* Qing Zhu,^1,* Wenhui Wu,¹ Xiaolin Xu,¹ Xiaoyu Wang,³ Shen Gao,³ Kehai Liu<sup>1

1</sup>Department of Biopharmaceutics, College of Food Science and Technology, Shanghai Ocean University, Shanghai, China; ²Shanghai Engineering Research Center of Aquatic-Product Processing and Preservation, Shanghai, China; ³Department of Pharmaceutics, Changhai Hospital, Second Military Medical University, Shanghai China

^*The first two authors contributed equally to this work

Background: Chitosan shows particularly high biocompatibility and fairly low cytotoxicity. However, chitosan is insoluble at physiological pH. Moreover, it lacks charge, so shows poor transfection. In order to develop a new type of gene vector with high transfection efficiency and low cytotoxicity, amphiphilic chitosan was synthesized and linked with low-molecular weight polyethylenimine (PEI).
Methods: We first synthesized amphiphilic chitosan – N-octyl-N-quatenary chitosan (OTMCS), then prepared degradable PEI derivates by cross-linking low-molecular weight PEI with amphiphilic chitosan to produce a new polymeric gene vector (OTMCS–PEI). The new gene vector was characterized by various physicochemical methods. We also determined its cytotoxicity and gene transfecton efficiency in vitro and in vivo.
Results: The vector showed controlled degradation. It was very stable and showed excellent buffering capacity. The particle sizes of the OTMCS–PEI/DNA complexes were around 150–200 nm with proper zeta potentials from 10 mV to 30 mV. The polymer could protect plasmid DNA from being digested by DNase I at a concentration of 2.25 U DNase I/µg DNA. Furthermore, they were resistant to dissociation induced by 50% fetal bovine serum and 1100 µg/mL sodium heparin. OTMCS–PEI revealed lower cytotoxicity, even at higher doses. Compared with PEI 25 KDa, the OTMCS–PEI/DNA complexes also showed higher transfection efficiency in vitro and in vivo.
Conclusion: OTMCS–PEI was a potential candidate as a safe and efficient gene vector for gene therapy.

Keywords: nonviral gene vector, polyethylenimine, transfection efficiency, cytotoxicity

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