Biotechnology and Bioprocess Engineering 2021; 26(4): 586-594  
Evaluation of Lipid-polyethylenimine Conjugates as Biocompatible Carriers of CpG Oligodeoxynucleotides to Macrophages
Jiwon Yang, Eun Seo Choi, Gayeon You, and Hyejung Mok
Jiwon Yang, Eun Seo Choi, Gayeon You, Hyejung Mok*
Department of Bioscience and Biotechnology, Konkuk University, Seoul 05029, Korea
Tel: +82-2-450-0448
These authors contributed equally to this work.
Received: November 17, 2020; Revised: December 31, 2020; Accepted: January 4, 2021; Published online: August 30, 2021.
© The Korean Society for Biotechnology and Bioengineering. All rights reserved.

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License ( which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Considering the potent immune stimulation by CpG oligodeoxynucleotides (CpGs), the development of CpG carriers is a prerequisite for efficient cancer immunotherapy. In this study, we conjugated 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[hydroxyl succinimidyl (polyethylene glycol)] (DSPE-PEG-NHS) with polyethylenimine (PEI) to develop a PEI-PEG-DSPE conjugate that can serve as a biocompatible and efficient CpG carrier. Five types of PEIPEG-DSPE conjugates were developed, each with different molecular weights of PEI and different degrees of DSPEPEG modification, and all exhibited significantly lower cytotoxicity. In particular, compared to CpG delivery via natural PEI, delivery with PEI (25 kDa)-PEG-DSPE and DSPE-PEG-NHS/(amine groups of PEI) at a molar ratio of 0.1 resulted in a higher uptake of CpGs into RAW264.7 cells, probably because of the presence of a hydrophobic lipid moiety. In addition, PEI-PEG-DSPE/CpG complexes triggered significant cytokine secretion (TNF-α) from RAW264.7 cells, comparable to that triggered by PEI/CpG complexes. Thus, PEI-PEG-DSPE conjugates could serve as biocompatible and efficient carriers of the immune stimulator CpG to the macrophages.
Keywords: polyethylenimine (PEI), lipid, conjugate, CpG oligodeoxynucleotide, macrophage

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