Novel branched poly(ethylenimine) - Cholesterol water-soluble lipopolymers for gene delivery

Dong An Wang, Ajit S. Narang, Malak Kotb, A. Osama Gaber, Duane D. Miller, Sung Wan Kim, Ram I. Mahato

Research output: Contribution to journalArticlepeer-review

228 Scopus citations


A novel water-soluble lipopolymer was synthesized by linking cholesteryl chloroformate to the secondary amino groups of branched poly(ethylenimine) (PEI) of 1800 and 10000 Da. Conjugation through PEI secondary amines gives this newly synthesized lipopolymer (abbreviated as PEI-Chol) special advantage over our previously synthesized lipopolymers, which utilized the primary amino groups for conjugation, as the primary amino groups have a significant role in DNA condensation. Also, significantly, only one cholesterol molecule was grafted onto each PEI molecule (confirmed by 1H NMR and MALDI-TOF mass spectrometry), leaving enough space for the steric interactions of the PEI's primary amines with the DNA. The PEI-Chol lipopolymer was characterized for the critical micellar concentration (cmc), buffer capacity, DNA condensation (by band retardation and circular dichroism), in vitro transfection efficiency, and cell viability. The cmcs of PEI-Chol 1800 and PEI-Chol 10000 were 496.6 and 1330.5 μg/mL, respectively. The acid-base titration indicated high buffering capacity of the polymers around the pH range of 5-7, which indicated their potential for buffering in the acidic pH environment of the endosomes. The band retardation studies indicated that efficient condensation of the plasmid DNA could be achieved using these lipopolymers. The circular dichroism spectra indicated a change in DNA conformation and adoption of lower energy state upon condensation with these lipopolymers when an N/P ratio of 2.5/1 or above was formulated. The mean particle size of these complexes was in the range 110-205 nm, except for the complexes prepared using PEI of 1800 Da, which had a mean particle size of 384 ± 300 nm. The ζ potential of DNA complexes prepared using PEI-Chol 1800, PEI-Chol 10000 and PEI of 1800, 10000, and 25000 Da at an N/P ratio of 15/1 was in the range 23-30 mV and was dependent on the N/P ratios. The in vitro transfection of PEI-Chol/pCMS-EGFP complexes in Jurkat cells showed high levels of expressed Green Fluorescent Protein (GFP) with little toxicity as determined by flow cytometry. These novel water-soluble lipopolymers provided good transfection efficiency with other desirable characteristics such as water solubility, free primary amino groups for efficient DNA condensation and high buffer capacity that indicated the possibility of efficient endosomal release.

Original languageEnglish (US)
Pages (from-to)1197-1207
Number of pages11
Issue number6
StatePublished - Nov 2002

ASJC Scopus subject areas

  • Bioengineering
  • Biomaterials
  • Polymers and Plastics
  • Materials Chemistry


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