DOPE (1,2-Dioleoyl-sn-glycero-3-phosphoethanolamine)

DOPE (1,2-Dioleoyl-sn-glycero-3-phosphoethanolamine) is a neutral phospholipid containing two unsaturated oleic acid chains (C18:1). DOPE has a wide range of applications in biofilm research and drug delivery systems, especially as one of the components in liposomes or lipid nanoparticles (LNPs). It can work synergistically with other phospholipid molecules or cholesterol to modulate the physical and chemical properties of membranes, thereby optimizing the stability and delivery efficiency of drug or gene delivery systems^[1][2].

In vitro, DC-Chol/DOPE liposomes (molar ratios 1:1, 2:3, 1:2) were prepared at 4µmol/mL DC-Chol with 4, 6, or 8µmol/mL DOPE respectively, then diluated in 20µL HEPES buffer and incubated with 20µL of pDNA (1µg) at room temperature for 25min. Liposome/pDNA complexes containing 0.5µg pDNA were added to HepG2 cells for 8h. There was no significant difference in pDNA binding affinity between DC-Chol/DOPE liposomes containing various molar ratios of DC-Chol/DOPE. After transfection, cell viability was about 80% and the cytotoxicity of DC-Chol/DOPE liposomes containing a relatively high DOPE content was relatively low^[3]. HEK-293, mouse colon cancer (CT-26), and human tongue squamous cell carcinoma (CAL-27) cells were incubated with two mono cationic lipids Toc-Cim liposomes or Chol-Cim liposomes with lipid/DOPE molar ratio=1:1 at concentrations of 10, 20, 40, and 80μg/mL and lipid/pDNA ratios of lipoplexes ranging from 1:1 to 8:1 for 4h. All the liposomal concentrations and N/P ratios, the synthesized lipids exhibited limited cytotoxicity (more than 80% of cell viability) except at 80μg/mL liposomal concentration and 8:1 lipid/pDNA ratio. at 4:1 and 2:1 lipid/pDNA ratios, the Toc-Cim:pCMV-β-gal were produced the most efficient as closely to lipofectamine:pCMV-β-gal in the HEK-293 cell line compared to Chol-Cim:pCMV- β-gal. Toc-Cim:pCMV-β-gal at a 2:1 lipid/pDNA ratio is as effective against the CT-26 cell line as compared to the CAL-27 cell line^[4].

In vivo, DC-Chol (1.046mg), DOPE (1.451mg; 52.2mol%) and PEG2000-DSPE (0.281mg; 2.0 mol%) were mixed first to produce liposome. Next, p_shEg5@LS lipoplexes were prepared by mixing cationic liposomes with pAAV-shEg5 plasmids, and then become a final concentration of 0.89mg/mL at liposome/pDNA ratio = 1.65:1 in HBG buffer. A2780 tumor-bearing BALB/c nude mice intravenously administered with Cy5.5-p_shEg5@LS (1.5mg/kg) via tail vein showed a significant delay in tumor growth. The tumor tissues were significantly reduced in weight (58.0% reduction) at the completion of experiment (two weeks after injection)^[5]. The optimized formulation of 306-O12B LNP had 50% leading tail-branched bioreducible lipidoid (306-O12B), 38.5% cholesterol, 10% DOPC, and 1.5% DMG-PEG molar composition with a 7.5:1 weight ratio of 306-O12B/mRNA. C57BL/6 mice were intravenously administrated with 306-O12B LNPs containing Cas9 mRNA and Angptl3-targeting single-guide RNA (sgAngptl3) with a total RNA dose of 3.0mg/kg. At day 7 post-injection, 306-O12B LNP-mediated delivery resulted in a median editing rate of 38.5% in liver. The serum ANGPTL3 protein, LDL-C, and TG levels in 306-O12B LNP treatment group (65.2, 56.8, and 29.4% reductions, respectively)^[6].

References:
[1] MacDonald R C, Rakhmanova V A, Choi K L, Rosenzweig H S, Lahiri M K. O-ethylphosphatidylcholine: A metabolizable cationic phospholipid which is a serum-compatible DNA transfection agent. J Pharm Sci. 1999 Sep;88(9):896-904.
[2] Benedicto E A, Farbiak L, Ramírez M M, et al. Optimization of phospholipid chemistry for improved lipid nanoparticle (LNP) delivery of messenger RNA (mRNA). Biomater Sci. 2022 Jan 18;10(2):549-559.
[3] Chen Y, Sun J, Ying Y, et al. Complexes containing cationic and anionic pH-sensitive liposomes: comparative study of factors influencing plasmid DNA gene delivery to tumors. Int J Nanomedicine. 2013:8:1573-93.
[4] Manturthi S, Bhattacharya D, Sakhare K R, Narayan K P, Patri S V. Cimetidine-Based Cationic Amphiphiles for In Vitro Gene Delivery Targetable to Colon Cancer. ACS Omega. 2022 Aug 25;7(35):31388-31402.
[5] Seraj S, Lee J J, Ahn H J. Systemic delivery of Eg5 shRNA-expressing plasmids using PEGylated DC-Chol/DOPE cationic liposome: Long-term silencing and anticancer effects in vivo. Biochem Pharmacol. 2019 Aug:166:192-202.
[6] Qiu M, Glass Z, Chen J J. Lipid nanoparticle-mediated codelivery of Cas9 mRNA and single-guide RNA achieves liver-specific in vivo genome editing of Angptl3. Proc Natl Acad Sci U S A. 2021 Mar 9;118(10):e2020401118.